Question about 1999 BMW 323 Series

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Tank leak diagnosis pump reed switch not open

(141) 8D EUIII PO440 OBDIII P1477 tank leak diagnosis pump reed switch not open

Posted by Anonymous on

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6ya6ya
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SOURCE: I have freestanding Series 8 dishwasher. Lately during the filling cycle water hammer is occurring. How can this be resolved

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Posted on Jan 02, 2017

duane_wong
  • 6826 Answers

SOURCE: P1477, Leakage Diagnostic Pump Reed Switch Did Not

Sounds like it has something to do with either the fuel system, more specifically in the evaporative fuel portion of the car.

A reed switch definition follows from Wikipedia:

The reed switch is an electrical switch operated by an applied magnetic field. It was invented at Bell Telephone Laboratories in 1936 by W. B. Ellwood.

Some people have changed the charcoal canister on their BMWs with this Malfunction Code, but that did not fix the problem.

Some people have changed the air filter and that didn't fix the problem.

Good luck on this repair.

Posted on Nov 12, 2010

  • 2 Answers

SOURCE: p1477 reed switch not open-

Im going throught this problem also P1477 code on my E46/99 bmw 328i, also dont forget to check all the vacume lines, it is very common on this car that the hoses they use go rotten very quick, along with the intake tubes or elbows, i found massive holes on my mine also many vacume lines damaged, i still have the 1477 code, but ive seen various post were people swapped the fuel breather valve, i checked all the canister tours the rear of the vehicle, they all seemed fine , no broken lines, everything is tight but the fuel breather valve its only between 80 to 100$, compare to the 350$ canister... go figure, and its fixed quite a few cars, so ill give it try, wipe the codes, and hope it doesnt come back, good luck....

Posted on Sep 27, 2012

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I have 99 bmw 323i.i ran it hot and got prob fixed and now the eml and a triangle with circle around it comes on dash and car has no power.feels like it has a rev limiter.wats wrong with my car


have throttle body checked also the MDK throttle motor,
make sure that the dealer has followed service bulletin 12 07 99 for procedure to replace the MDK throttle motor
also have them check for codes,here are some codes,
it could be an expensive job,have them check everything,it is most likely the throttle motor,,throttle body is 600 if they switch it,dont let them do it without checking throttle motor,
codes,
MS41, MS42 and MS43 engine DME bmw codes...
• 1 Ignition coil Cyl 2
• 2 Ignition coil Cyl 4
• 3 Ignition coil Cyl 6
• 5 Fuel injector Cyl 2
• 6 Fuel injector Cyl 1
• 8 Air Flow Meter (HFM)
• 10 Coolant Temperature Sensor
• 11 Tank Pressure Sensor (EVAP System) or Radiator Outlet Temp (MS43)
• 12 TPS or Plausibility - Maximum Coolant Temp (MS43)
• 13 Plausibility- Radiator Outlet Temp
• 14 Intake Air Temperature Sensor
• 15 Plausibility - Cut Out Time
• 16 AirCon Compressor - PWM Signal or Plausibility Intake Air Temp (MS43)
• 17 Plausibility - Engine Coolant Temp
• 18 EWS Signal or Camshaft Sensor (MS43)
• 19 Activation VANOS Inlet Valve or Exhaust Valve (MS43)
• 20 "CHECK ENGINE" Light Failure
• 21 VANOS -Electrical Fault or Activation VANOS Inlet Valve (MS43)
• 22 Fuel Injector Cyl 3
• 23 Fuel Injector Cyl 6
• 24 Fuel Injector Cyl 4
• 25 Lambda Sensor Heater -Bank 1
• 27 Idle Control Valve - Malfunction
• 29 Ignition Coil Cyl 1
• 30 Ignition Coil Cyl 3
• 31 Ignition Coil Cyl 5
• 33 Fuel Injector Cyl 5
• 35 Aux. Air Injection System Relay
• 36 DME Main Relay
• 37 DME Main Relay : Delay
• 38 Clutch Switch -Plausibility
• 39 Brake Light Switch or Brake Light Test Switch
• 40 Brake Light Switch or Pedal Value Signal
• 42 Multi Function Steering Wheel- Plausibility
• 43 Multi Function Steering Wheel: Button
• 45 Multi Function Steering Wheel: Port
• 47 Temp Sensor -Downstream of Pre-Cat or Torque Limitation Level 1 (MS43)
• 48 DME Control Unit -Self Test 1
• 49 DME Control Unit or Torque Monitoring Level 2 (MS43)
• 50 EVAP Control Valve or Response Monitoring Level 2 (MS43)
• 51 Shut-off Valve -Charcoal Filter or Request Control Unit Reset (MS43)
• 52 Solenoid Valve -Exhaust Flap
• 53 Idle Speed Actuator
• 55 Lambda Sensor Heater -Bank 2
• 56 Ignition Current Feedback Resistor - Open Circuit
• 57 Knock sensor -Bank 1
• 58 DME Control Unit -Self Test 2
• 59 Knock Sensor -Bank 2
• 61 Lambda Sensor Heater -Bank 2 Post Cat
• 62 Aux. Air Injection System -Switching Valve
• 63 DME Control Unit or Ambient Temp Signal via CAN (MS43)
• 64 Plausibility - Ambient Temperature
• 65 Camshaft Position Sensor (Inlet MS43)
• 66 DME Control Unit
• 67 DME Control Unit
• 68 Tank Venting Valve
• 69 Fuel Pump Relay
• 70 DME Control Unit
• 71 DME Control Unit
• 72 DME Control Unit
• 74 AirCon Compressor Relay
• 75 Lambda Sensor Voltage -Bank 1
• 76 Lambda Sensor Voltage -Bank 2
• 77 Lambda Sensor Voltage -Bank 1 Post Cat
• 78 Lambda Sensor Voltage -Bank 2 Post Cat
• 79 Lambda Sensor Heater -Bank 1 Post Cat
• 80 ABS/ASC interface
• 81 MSR Signal -Active too Long
• 82 ABS/ASC Interface -Advance Adjustment
• 83 Crankshaft Sensor
• 90 Exhaust Temperature Pre Cat Conv - Bank 1
• 91 Exhaust Temperature Pre Cat Conv - Bank 2
• 92 Exhaust Temperature Post Cat Conv -Bank 1
• 93 Exhaust Temperature Post Cat Conv -Bank 2
• 94 Auxiliary Air -Air Mass Flow Sensor
• 95 Auxiliary Air Valve or Auxiliary Air Hose Blocked
• 96 Auxiliary Air Pump - Function
• 97 Auxiliary Air -Flow Rate too Low
• 98 Auxiliary Air -Flow Rate too High
• 99 Auxiliary Air Valve Jammed Open
• 100 DME Control Unit -Self-Test Failed
• 103 VANOS Error -Inlet Camshaft
• 104 VANOS Error -Exhaust Camshaft
• 105 VANOS Error -Position Inlet Camshaft
• 106 VANOS Error -Position Exhaust Camshaft
• 109 Throttle Valve Plausibility
• 110 Pedal Sensor Value Potentiometer 1
• 111 Pedal Sensor Value Potentiometer 2
• 112 TPS Potentiometer 1
• 113 TPS Potentiometer 2
• 114 Throttle Valve Final Stage
• 115 Reference Voltage -Voltage Regulator 1 or Throttle Pedal Adaptation (MS43)
• 116 Reference Voltage -Voltage Regulator 2
• 117 Plausibility -Pedal Position Sensor 1/2
• 118 Plausibility -TPS 1/2 or TPS1/Airflow Plausibility (MS43)
• 119 Throttle Valve Sensor -Mechanical Error or TPS2/Airflow Plausibility (MS43)
• 120 Plausibility Pedal Sensor or TPS
• 122 Engine Oil Temperature
• 123 Map Cooling Thermostat Control
• 124 Activation DISA Solenoid
• 125 Activation Electric Fan
• 126 Activation Tank Leak Pump Solenoid
• 127 Activation Pump Solenoid
• 128 DME/EWS Communication
• 129 CAN Signal SMG 1
• 130 CAN Signal ASC -Timeout
• 131 CAN Signal Instrument Cluster -Timeout
• 132 CAN Signal Instrument Cluster -Timeout
• 133 CAN Signal ASC -Timeout
• 134 SMG Intervention -Plausibility
• 135 Throttle Valve Re-Adaptation Required
• 136 Throttle Valve -Spring Test and Limp-home Position Failed
• 137 CAN Signal -Steering Angle Sensor
• 139 CAN Signal -Tank Level Sensor
• 140 Tank Leak Pump Solenoid - Reed Switch Open or Output Stage (MS43)
• 141 Tank Leak Pump Solenoid - Reed Switch Stuck Closed or Tank Level Sensor (MS43)
• 142 Tank Leak Pump Solenoid - Reed Switch Stuck Open or DMTL Module (MS43)
• 143 Tank Ventilation or Tank Leakage (MS43)
• 144 Fuel System - Large Leak Recognised
• 145 Fuel System - Small Leak Recognised
• 146 EVAP System Leak Detected (Small Leak) or Pedal Sensor Supply Voltage Pot 1 (MS43)
• 147 Pedal Position Sensor Potentiometer Supply Channel 1 (Pot 2 MS43)
• 149 Air Flow Sensor or Pedal Value Sensor Mismatch
• 150 Lambda Post Cat Bank 1 Max Limit
• 151 Lambda Post Cat Bank 2 Max Limit
• 152 Lambda Post Cat Bank 1 Min Limit
• 153 Lambda Pre Cat Bank 2 Max Limit
• 154 Lambda Pre Cat Bank 2 Min Limit
• 155 Lambda Pre Cat Bank 2 No Signal
• 156 Lambda Pre Cat Bank 1 No Signal
• 157 Lambda Post Cat Bank 1 Min Limit
• 159 Lambda Post Cat Bank 2 Max Limit
• 160 Lambda Post Cat Bank 2 (MS41) or Throttle Valve Stuck
• 161 Throttle Valve - Stuck
• 162 Throttle Valve -Control Deviation
• 168 Pedal Position Sensor Pot Supply 1 or MAP Cooling Thermostat Jammed (MS43)
• 169 Throttle Valve Output Stage Cut off after Fault
• 170 DME Control Unit -Self Test Failed
• 171 Plausibility - Throttle Valve
• 172 Pedal Sensor Potentiometer 1/2 Short Circuit
• 173 TPS Potentiometer 1/2 Short Circuit
• 174 Throttle Valve Potentiometer 1/2 Adaptation
• 175 Pedal Sensor 1 Adaptation
• 176 Pedal Sensor 2 Adaptation
• 186 Voltage Post Cat Bank 1
• 187 Voltage Post Cat Bank 2
• 188 Voltage Pre Cat Bank 1
• 189 Voltage Pre Cat Bank 2
• 190 EVAP -Reed Switch Open or Voltage Post Cat Bank 1 (MS43)
• 191 EVAP -Reed Switch Closed or Voltage Post Cat Bank 2 (MS43)
• 192 EVAP -Reed Switch Open
• 193 EVAP -Check Hoses
• 194 EVAP -Large Leak Detected
• 195 EVAP -Small Leak Detected
• 196 EVAP -Electrical Valve from LDP Pump or Barometric Pressure Sensor (MS43)
• 197 EVAP -Barometric Pressure Sensor
• 198 Cat Efficiency during Start -Bank 1
• 199 Cat Efficiency during Start -Bank 2
• 200 Lambda Regulation Bank 1 Pre Cat
• 201 Lambda Regulation Bank 2 Pre Cat
• 202 Lambda Regulation Bank 1 Post Cat
• 203 Lambda Regulation Bank 2 Post cat
• 204 Idle Control System -Idle speed not plausible
• 208 EWS -RPM Signal Error
• 209 EWS -Message Error
• 210 Ignition Feedback Resistor (ZSR)
• 211 Idle Speed Actuator -Mechanical
• 212 VANOS Bank 1 -Mechanical
• 214 Vehicle Speed Signal (VSS)
• 215 Lambda Sensor Bank 1 or ASC/MSR/EML -Interface not plausible
• 216 Lambda Sensor Bank 2 or EGS Position Signal
• 217 CAN bus error -EGS Signal not present
• 218 CAN module -Warning
• 219 CAN module -CAN Offline
• 220 Lambda Voltage Range Bank 1 Sensor 1
• 221 Lambda Voltage Range Bank 2 Sensor 1
• 222 Low Coolant Temperature or Lambda Sensor Control (MS43)
• 223 Lambda Sensor Switching Bank 1 Sensor 2
• 224 Lambda Sensor Switching Bank 2 Sensor 2
• 225 Cat Efficiency Bank 1
• 226 Cat Efficiency Bank 2
• 227 Mixture Deviation Bank 1
• 228 Mixture Deviation Bank 2
• 229 Lambda Sensor Switching Bank 1
• 230 Lambda Sensor Switching Bank 2
• 231 Lambda Sensor Switching Bank 1 Pre Cat
• 232 Lambda Sensor Switching Bank 2 Pre Cat
• 233 Catalytic Converter Overall Efficiency Bank 1
• 234 Catalytic Converter Overall Efficiency Bank 2
• 235 Lambda Heater Bank 1 Post Cat or Pre Cat Signal (MS43)
• 236 Lambda Heater Bank 2 Post Cat or Pre Cat Signal (MS43)
• 238 Misfire Cyl 1
• 239 Misfire Cyl 2
• 240 Misfire Cyl 3
• 241 Misfire Cyl 4
• 242 Misfire Cyl 5
• 243 Misfire Cyl 6
• 244 Crankshaft Interval Timing
• 245 Aux Air Injection System Bank 1
• 246 Aux Air Injection System Bank 2
• 247 Aux Air Injection System -Incorrect Flow Detected
• 248 Pre Cat Converter Efficiency -Bank 1
• 249 Pre Cat Converter Efficiency -Bank 2
• 250 Tank Venting Valve -Function
• 251 Tank Ventilation Diagnosis Error
• 252 Tank Ventilation System Vacuum
• 253 Activated Charcoal Filter Shut-off Valve Stuck Shut
• 254 Tank Ventilation System -Large Air Leak
• 255 Tank Ventilation System -Valve Stuck Open

Apr 03, 2015 | 1999 BMW 323i

2 Answers

Diagnosis code Po440 on Oldsmobile 88 ls


That is P0440
Difintion is: Leak in the Evpaorative fuel emission system. Possible common cause loose or defective gas cap.

May 30, 2012 | Cars & Trucks

1 Answer

P1477 reed switch not open- changed gas cap last week 2000 328ci


Im going throught this problem also P1477 code on my E46/99 bmw 328i, also dont forget to check all the vacume lines, it is very common on this car that the hoses they use go rotten very quick, along with the intake tubes or elbows, i found massive holes on my mine also many vacume lines damaged, i still have the 1477 code, but ive seen various post were people swapped the fuel breather valve, i checked all the canister tours the rear of the vehicle, they all seemed fine , no broken lines, everything is tight but the fuel breather valve its only between 80 to 100$, compare to the 350$ canister... go figure, and its fixed quite a few cars, so ill give it try, wipe the codes, and hope it doesnt come back, good luck....

Jun 13, 2011 | 2000 BMW 3 Series

1 Answer

Po440 code


CODE PO440 IS EVAP SYSTEM MALFUNCTION CONDITIONS. POSSIBLE CAUSES CHARCOAL CANISTER IS LOADED WITH FUEL OR MOISTURE. FUEL FILLER CAP IS LOOSE CROSS THREADED DAMAGED OR WRONG PART. FUEL TANK FUEL FILLER NECK OR FUEL SENDING UNIT O RING IS LEAKING. FUEL TANK PRESSURE SENSOR IS DAMAGED OR DISCONNECTED.OR FAILED.FUEL TANK VAPOR LINES IS CLOGGED DAMAGED OR DISCONNECTED.PURGE VALVE VAPOR LINE IS CLOGGED DAMAGED OR DISCONNECTED. PURGE OR VENT SOLENOID POWER CIRCUIT IS OPEN CHECK THE FUSE.PCM HAS FAILED.

Jan 12, 2011 | 2001 Chevrolet Venture

1 Answer

Check engine light is on and when checked it pulls a malfunction code (code P1494) leak detection switch or mechanical failure. Is it still under warranty under the emissions? It is a 2001 Jeep Grand...


First off, a model year 2001, its possible still covered under the 5 year/50,000 mile emissions warranty. That's federal law. So you should not have had to pay a penny for that repair since the Leak Detection Pump is an emission control device.

As is the Charcoal Canister. If that is bad there should be no charge for repair or replacement. I hope you saved the receipts because I think they owe you a bunch of money. If they give you an argument about it, call Chrysler and they will take care of it.

Now, are you ready to learn more about the Leak Detection Pump then you will ever need to know? Good! Here it is!

Leak Detection Pump (LDP) Operation And Diagnosis:
* P0442-Evap Leak Monitor 0.040" Leak Detected
* P0455-Evap Leak Monitor Large Leak Detected
* P0456-Evap Leak Monitor 0.020" Leak Detected
* P1486-Evap Leak Monitor Pinched Hose Found
* P1494-Leak Detection Pump SW Or Mechanical Fault
* P1495-Leak Detection Pump Solenoid Circuit

Introduction:
The evaporative emission system is designed to prevent the escape of fuel vapors from the fuel system. Leaks in the system, even small ones, can allow fuel vapors to escape into the atmosphere.

Government regulations (remember I said that?) require on-board testing to make sure that the evaporative (EVAP) system is functioning properly. The leak detection system tests for EVAP system leaks and blockage. It also performs self-diagnostics.

During self-diagnostics, the Powertrain Control Module (PCM) first checks the Leak Detection Pump (LDP) for electrical and mechanical faults. If the first checks pass, the PCM then uses the LDP to seal the vent valve and pump air into the system to pressurize it.

If a leak is present, the PCM will continue pumping the LDP to replace the air that leaks out. The PCM determines the size of the leak based on how fast/long it must pump the LDP as it tries to maintain pressure in the system.

EVAP Leak Detection System Components:
Service Port: Used with special tools like the Miller Evaporative Emissions Leak Detector (EELD) to test for leaks in the system.

EVAP Purge Solenoid: The PCM uses the EVAP purge solenoid to control purging of excess fuel vapors stored in the EVAP canister. It remains closed during leak testing to prevent loss of pressure.

EVAP Canister The EVAP canister stores fuel vapors from the fuel tank for purging. EVAP Purge Orifice: Limits purge volume.

EVAP System Air Filter: Provides air to the LDP for pressurizing the system. It filters out dirt while allowing a vent to atmosphere for the EVAP system.

Leak Detection Pump (LDP) Components:
The main purpose of the LDP is to pressurize the fuel system for leak checking. It closes the EVAP system vent to atmospheric pressure so the system can be pressurized for leak testing. The diaphragm is powered by engine vacuum. It pumps air into the EVAP system to develop a pressure of about 7.5' H20(1/4) psi. A reed switch in the LDP allows the PCM to monitor the position of the LDP diaphragm. The PCM uses the reed switch input to monitor how fast the LDP is pumping air into the EVAP system. This allows detection of leaks and blockage.

The LDP assembly consists of several parts. The solenoid is controlled by the PCM, and it connects the upper pump cavity to either engine vacuum or atmospheric pressure. A vent valve closes the EVAP system to atmosphere, sealing the system during leak testing. The pump section of the LDP consists of a diaphragm that moves up and down to bring air in through the air filter and inlet check valve, and pump it out through an outlet check valve into the EVAP system.

The diaphragm is pulled up by engine vacuum, and pushed down by spring pressure, as the LDP solenoid turns on and off. The LDP also has a magnetic reed switch to signal diaphragm position to the PCM. When the diaphragm is down, the switch is closed, which sends a 12 V (system voltage) signal to the PCM. When the diaphragm is up, the switch is open, and there is no voltage sent to the PCM. This allows the PCM to monitor LDP pumping action as it turns the LDP solenoid on and off.

LDP At Rest (Not Powered):
When the LDP is at rest (no electrical/vacuum) the diaphragm is allowed to drop down if the internal (EVAP system) pressure is not greater than the return spring. The LDP solenoid blocks the engine vacuum port and opens the atmospheric pressure port connected through the EVAP system air filter. The vent valve is held open by the diaphragm. This allows the canister to see atmospheric pressure.

Diaphragm Upward Movement:
When the PCM energizes the LDP solenoid, the solenoid blocks the atmospheric port leading through the EVAP air filter and at the same time opens the engine vacuum port to the pump cavity above the diaphragm. The diaphragm moves upward when vacuum above the diaphragm exceeds spring force. This upward movement closes the vent valve. It also causes low pressure below the diaphragm, unseating the inlet check valve and allowing air in from the EVAP air filter. When the diaphragm completes its upward movement, the LDP reed switch turns from closed to open.

Diaphragm Downward Movement:
based on reed switch input, the PCM de-energizes the LDP solenoid, causing it to block the vacuum port, and open the atmospheric port. This connects the upper pump cavity to atmosphere through the EVAP air filter. The spring is now able to push the diaphragm down. The downward movement of the diaphragm closes the inlet check valve and opens the outlet check valve pumping air into the evaporative system. The LDP reed switch turns from open to closed, allowing the PGM to monitor LDP pumping (diaphragm up/down) activity. During the pumping mode, the diaphragm will not move down far enough to open the vent valve.

The pumping cycle is repeated as the solenoid is turned on and off. When the evaporative system begins to pressurize, the pressure on the bottom of the diaphragm will begin to oppose the spring pressure, slowing the pumping action. The PCM watches the time from when the solenoid is de-energized, until the diaphragm drops down far enough for the reed switch to change from opened to closed. If the reed switch changes too quickly, a leak may be indicated. The longer it takes the reed switch to change state, the tighter the evaporative system is sealed. If the system pressurizes too quickly, a restriction somewhere in the EVAP system may be indicated.

Pumping Action:
During portions of this test, the PCM uses the reed switch to monitor diaphragm movement. The solenoid is only turned on by the PCM after the reed switch changes from open to closed, indicating that the diaphragm has moved down. At other times during the test, the PCM will rapidly cycle the LDP solenoid on and off to quickly pressurize the system. During rapid cycling, the diaphragm will not move enough to change the reed switch state. In the state of rapid cycling, the PCM will use a fixed time interval to cycle the solenoid.
The Charcoal Canister

EVAP/Purge Solenoid:
The duty cycle EVAP canister purge solenoid (DCP) regulates the rate of vapor flow from the EVAP canister to the intake manifold. The Powertrain Control Module (PCM) operates the solenoid.

During the cold start warm-up period and the hot start time delay, the PCM does not energize the solenoid. When de-energized, no vapors are purged. The PCM de-energizes the solenoid during open loop operation.

The engine enters closed loop operation after it reaches a specified temperature and the time delay ends. During closed loop operation, the PCM cycles (energizes and de-energizes) the solenoid 5 or 10 times per second , depending upon operating conditions. The PCM varies the vapor flow rate by changing solenoid pulse width. Pulse width is the amount of time that the solenoid is energized. The PCM adjusts solenoid pulse width based on engine operating condition.

Vapor Canister:
A maintenance free, EVAP canister is used on all vehicles. The EVAP canister is filled with granules of an activated carbon mixture. Fuel vapors entering the EVAP canister are absorbed by the charcoal granules.

Fuel tank pressure vents into the EVAP canister. Fuel vapors are temporarily held in the canister until they can be drawn into the intake manifold. The duty cycle EVAP canister purge solenoid allows the EVAP canister to be purged at predetermined times and at certain engine operating conditions.

Hope this helps.

Dec 14, 2010 | 2001 Jeep Grand Cherokee

2 Answers

Code P1477


Code P1477 means: EVAP LDP Circuit Malfunction. (It may just be a faulty gas cap)

Nov 16, 2010 | 2002 Mercury Sable

1 Answer

Leak detection pump sw or mechanical fault


can be caused by failure of the evaporation system leak detection pump or reed switch. When you turn your key on, the LDP sometimes comes on briefly to pressurize the fuel tank. The PCM enables a solenoid value in the pump to allow engine vacuum to shift a diaphram that pressurizes the system. Locate the LDP if the left rear bumper/fender well. With the engine running, remove the vacuum hose to see if vacuum from the engine is being supplied to the pump. If not, check the hose connection at the engine intake manifold. Repair or replace the hose as necessary to restore vacuum to the LDP.
If the engine vacuum is present, the problem may be with the pump or the electrical power to the pump solenoid. You can check the power to the solenoid by removing the connector and probing the connector with a 12 volt test light. Connect the test light clip to a ground point on the frame and probe the cable terminals. With the car running, one of the terminal should light the test light. If not, the problem is the wiring to the alternator. If the test light comes on, replace the LDP. Please let me know if you have any questions.


EVAP Leak Detection Pump Description & Operation
The evaporative emission system is designed to prevent the escape of fuel vapors from the fuel system. Leaks in the system, even small ones, can allow fuel vapors to escape into the atmosphere. Government regulations require onboard Testing to make sure that the evaporative (EVAP) system is functioning properly. The leak detection system tests for EVAP system leaks and blockage. It also performs self-diagnostics. During self-diagnostics, the Powertrain Control Module (PCM) first checks the Leak Detection Pump (LDP) for electrical and mechanical faults. If the first checks pass, the PCM then uses the LDP to seal the vent valve and pump air into the system to pressurize it. If a leak is present, the PCM will continue pumping the LDP to replace the air that leaks out. The PCM determines the size of the leak based on how fast/long it must pump the LDP as it tries to maintain pressure in the system.
The main purpose of the LDP is to pressurize the fuel system for leak checking. It closes the EVAP system vent to atmospheric pressure so the system can be pressurized for leak Testing. The diaphragm is powered by engine vacuum. It pumps air into the EVAP system to develop a pressure of about 0.25 psi. A reed switch in the LDP allows the PCM to monitor the position of the LDP diaphragm. The PCM uses the reed switch input to monitor how fast the LDP is pumping air into the EVAP system. This allows detection of leaks and blockage.
The LDP assembly consists of several parts. The solenoid is controlled by the PCM, and it connects the upper pump cavity to either engine vacuum or atmospheric pressure. A vent valve closes the EVAP system to atmosphere, sealing the system during leak Testing. The pump section of the LDP consists of a diaphragm that moves up and down to bring air in through the air filter and inlet check valve, and pump it out through an outlet check valve into the EVAP system. The diaphragm is pulled up by engine vacuum, and pushed down by spring pressure, as the LDP solenoid turns on and off.
The LDP also has a magnetic reed switch to signal diaphragm position to the PCM. When the diaphragm is down, the switch is closed, which sends a 12v (system voltage) signal to the PCM. When the diaphragm is up, the switch is open, and there is no voltage sent to the PCM. This allows the PCM to monitor LDP pumping action as it turns the LDP solenoid on and off.
Diaphragm Downward Movement
Based on reed switch input, the PCM de-energizes the LDP solenoid, causing it to block the vacuum port, and open the atmospheric port. This connects the upper pump cavity to atmosphere through the EVAP air filter. The spring is now able to push the diaphragm down. The downward movement of the diaphragm closes the inlet check valve and opens the outlet check valve pumping air into the evaporative system. The LDP reed switch turns from open to closed, allowing the PCM to monitor LDP pumping (diaphragm up/down) activity.
During the pumping mode, the diaphragm will not move down far enough to open the vent valve. The pumping cycle is repeated as the solenoid is turned on and off. When the evaporative system begins to pressurize, the pressure on the bottom of the diaphragm will begin to oppose the spring pressure, slowing the pumping action. The PCM watches the time from when the solenoid is de-energized, until the diaphragm drops down far enough for the reed switch to change from opened to closed. If the reed switch changes too quickly, a leak may be indicated. The longer it takes the reed switch to change state, the tighter the evaporative system is sealed. If the system pressurizes too quickly, a restriction somewhere in the EVAP system may be indicated.
Diaphragm Upward Movement
When the PCM energizes the LDP solenoid, the solenoid blocks the atmospheric port leading through the EVAP air filter and at the same time opens the engine vacuum port to the pump cavity above the diaphragm. The diaphragm moves upward when vacuum above the diaphragm exceeds spring force. This upward movement closes the vent valve. It also causes low pressure below the diaphragm, unseating the inlet check valve and allowing air in from the EVAP air filter. When the diaphragm completes its upward movement, the LDP reed switch turns from closed to open.

Removal & Installation
The Leak Detection Pump (LDP) is located under the left quarter panel behind the left/rear wheel. It is attached to a two-piece support bracket. The LDP and LDP filter are replaced (serviced) as one unit.

  1. Remove stone shield behind left/rear wheel. Drill out plastic rivets for removal.
  2. Remove 3 LDP mounting bolts.
  3. Remove support bracket brace bolt.
  4. Loosen, but do not remove 2 support bracket nuts at frame rail.
  5. To separate and lower front section of two-piece support bracket, remove 3 attaching bolts on bottom of support bracket. While lowering support bracket, disconnect LDP wiring clip.
  6. Disconnect electrical connector at LDP.
  7. Carefully remove vapor/vacuum lines at LDP.
  8. Remove LDP.

To Install:
  1. Position LDP and carefully install vapor/vacuum lines to LDP and LDP filter.
    WARNING The vapor/vacuum lines and hoses must be firmly connected. Check the vapor/vacuum lines at the LDP; LDP filter and EVAP canister purge solenoid for damage or leaks. If a leak is present, a Diagnostic Trouble Code (DTC) may be set.
  2. Connect electrical connector to LDP.
  3. While raising front section of support bracket, connect LDP wiring clip.
  4. Install 3 LDP mounting bolts.
  5. Join front and rear sections of two-piece support bracket by installing 3 bolts on bottom of support bracket. Do not tighten bolts at this time.
  6. Install support bracket brace bolt. Do not tighten bolt at this time.
  7. Tighten 2 support bracket nuts at frame rail and 3 support bracket bolts and brace bolt.
  8. Position stone shield behind left/rear wheel. Install new plastic rivets.
  9. jturcotte_55.gif

Nov 05, 2010 | 2000 Jeep Grand Cherokee

1 Answer

Code P1494


DTC P1494 - Leak Detection Pump Switch or Mechanical Fault

The causes are possibly an open or shorted switch sense circuit, a pump switch failure, or an open "fused ignition switch" output. First off, a model year 2001 is will still covered under the emissions warranty. That's federal law. So you should not have had to pay a penny for that repair since the Leak Detection Pump is an emission control device.

As is the Charcoal Canister. If that is bad there should be no charge for repair or replacement. I hope you saved the receipts because I think they owe you a bunch of money. If they give you an argument about it, call Chrysler and they will take care of it.

Now, are you ready to learn more about the Leak Detection Pump then you will ever need to know? Good! Here it is!

Leak Detection Pump (LDP) Operation And Diagnosis:

This article describes the theory of operation for the leak detection system. In addition, information is provided for each of the Diagnostic Trouble Codes (DTC's) as follows:

* P0442-Evap Leak Monitor 0.040" Leak Detected
* P0455-Evap Leak Monitor Large Leak Detected
* P0456-Evap Leak Monitor 0.020" Leak Detected
* P1486-Evap Leak Monitor Pinched Hose Found
* P1494-Leak Detection Pump SW Or Mechanical Fault
* P1495-Leak Detection Pump Solenoid Circuit

Introduction:
The evaporative emission system is designed to prevent the escape of fuel vapors from the fuel system. Leaks in the system, even small ones, can allow fuel vapors to escape into the atmosphere.

Government regulations (remember I said that?) require on-board testing to make sure that the evaporative (EVAP) system is functioning properly. The leak detection system tests for EVAP system leaks and blockage. It also performs self-diagnostics.

During self-diagnostics, the Powertrain Control Module (PCM) first checks the Leak Detection Pump (LDP) for electrical and mechanical faults. If the first checks pass, the PCM then uses the LDP to seal the vent valve and pump air into the system to pressurize it.

If a leak is present, the PCM will continue pumping the LDP to replace the air that leaks out. The PCM determines the size of the leak based on how fast/long it must pump the LDP as it tries to maintain pressure in the system.

EVAP Leak Detection System Components:
Service Port: Used with special tools like the Miller Evaporative Emissions Leak Detector (EELD) to test for leaks in the system.

EVAP Purge Solenoid: The PCM uses the EVAP purge solenoid to control purging of excess fuel vapors stored in the EVAP canister. It remains closed during leak testing to prevent loss of pressure.

EVAP Canister The EVAP canister stores fuel vapors from the fuel tank for purging. EVAP Purge Orifice: Limits purge volume.

EVAP System Air Filter: Provides air to the LDP for pressurizing the system. It filters out dirt while allowing a vent to atmosphere for the EVAP system.

Leak Detection Pump (LDP) Components:
The main purpose of the LDP is to pressurize the fuel system for leak checking. It closes the EVAP system vent to atmospheric pressure so the system can be pressurized for leak testing. The diaphragm is powered by engine vacuum. It pumps air into the EVAP system to develop a pressure of about 7.5' H20(1/4) psi. A reed switch in the LDP allows the PCM to monitor the position of the LDP diaphragm. The PCM uses the reed switch input to monitor how fast the LDP is pumping air into the EVAP system. This allows detection of leaks and blockage.

The LDP assembly consists of several parts. The solenoid is controlled by the PCM, and it connects the upper pump cavity to either engine vacuum or atmospheric pressure. A vent valve closes the EVAP system to atmosphere, sealing the system during leak testing. The pump section of the LDP consists of a diaphragm that moves up and down to bring air in through the air filter and inlet check valve, and pump it out through an outlet check valve into the EVAP system.

The diaphragm is pulled up by engine vacuum, and pushed down by spring pressure, as the LDP solenoid turns on and off. The LDP also has a magnetic reed switch to signal diaphragm position to the PCM. When the diaphragm is down, the switch is closed, which sends a 12 V (system voltage) signal to the PCM. When the diaphragm is up, the switch is open, and there is no voltage sent to the PCM. This allows the PCM to monitor LDP pumping action as it turns the LDP solenoid on and off.

LDP At Rest (Not Powered):
When the LDP is at rest (no electrical/vacuum) the diaphragm is allowed to drop down if the internal (EVAP system) pressure is not greater than the return spring. The LDP solenoid blocks the engine vacuum port and opens the atmospheric pressure port connected through the EVAP system air filter. The vent valve is held open by the diaphragm. This allows the canister to see atmospheric pressure.

Diaphragm Upward Movement:
When the PCM energizes the LDP solenoid, the solenoid blocks the atmospheric port leading through the EVAP air filter and at the same time opens the engine vacuum port to the pump cavity above the diaphragm. The diaphragm moves upward when vacuum above the diaphragm exceeds spring force. This upward movement closes the vent valve. It also causes low pressure below the diaphragm, unseating the inlet check valve and allowing air in from the EVAP air filter. When the diaphragm completes its upward movement, the LDP reed switch turns from closed to open.

Diaphragm Downward Movement:
based on reed switch input, the PCM de-energizes the LDP solenoid, causing it to block the vacuum port, and open the atmospheric port. This connects the upper pump cavity to atmosphere through the EVAP air filter. The spring is now able to push the diaphragm down. The downward movement of the diaphragm closes the inlet check valve and opens the outlet check valve pumping air into the evaporative system. The LDP reed switch turns from open to closed, allowing the PGM to monitor LDP pumping (diaphragm up/down) activity. During the pumping mode, the diaphragm will not move down far enough to open the vent valve.

The pumping cycle is repeated as the solenoid is turned on and off. When the evaporative system begins to pressurize, the pressure on the bottom of the diaphragm will begin to oppose the spring pressure, slowing the pumping action. The PCM watches the time from when the solenoid is de-energized, until the diaphragm drops down far enough for the reed switch to change from opened to closed. If the reed switch changes too quickly, a leak may be indicated. The longer it takes the reed switch to change state, the tighter the evaporative system is sealed. If the system pressurizes too quickly, a restriction somewhere in the EVAP system may be indicated.

Pumping Action:
During portions of this test, the PCM uses the reed switch to monitor diaphragm movement. The solenoid is only turned on by the PCM after the reed switch changes from open to closed, indicating that the diaphragm has moved down. At other times during the test, the PCM will rapidly cycle the LDP solenoid on and off to quickly pressurize the system. During rapid cycling, the diaphragm will not move enough to change the reed switch state. In the state of rapid cycling, the PCM will use a fixed time interval to cycle the solenoid.

The Charcoal Canister

EVAP/Purge Solenoid:
The duty cycle EVAP canister purge solenoid (DCP) regulates the rate of vapor flow from the EVAP canister to the intake manifold. The Powertrain Control Module (PCM) operates the solenoid.

During the cold start warm-up period and the hot start time delay, the PCM does not energize the solenoid. When de-energized, no vapors are purged. The PCM de-energizes the solenoid during open loop operation.

The engine enters closed loop operation after it reaches a specified temperature and the time delay ends. During closed loop operation, the PCM cycles (energizes and de-energizes) the solenoid 5 or 10 times per second , depending upon operating conditions. The PCM varies the vapor flow rate by changing solenoid pulse width. Pulse width is the amount of time that the solenoid is energized. The PCM adjusts solenoid pulse width based on engine operating condition.

Vapor Canister:
A maintenance free, EVAP canister is used on all vehicles. The EVAP canister is filled with granules of an activated carbon mixture. Fuel vapors entering the EVAP canister are absorbed by the charcoal granules.

Fuel tank pressure vents into the EVAP canister. Fuel vapors are temporarily held in the canister until they can be drawn into the intake manifold. The duty cycle EVAP canister purge solenoid allows the EVAP canister to be purged at predetermined times and at certain engine operating conditions.

Hope helps (remember rated and comment this).

Jun 17, 2010 | 2001 Jeep Grand Cherokee

2 Answers

I have code po440 on my 2000 blazer..what's wrong??


CODE PO440 - EVAP ystem malfunction conditions. possible causes 1-charcoal canister is loaded with fuel or moisture. 2- the fuel filler cap is loose or damaged 3- fuel tank filler neck or fuel sending unit O ring is leaking 4- fuel tank pressure sensor is damaged disconnected or it failed.5- fuel tank vapor lines is clogged damaged or disconnected. 6 -purge valve vapor line is clogged damaged or disconnected.7- the purge or vent solenoid power circuit is open check the fuse.8-pcm has failed.

Dec 26, 2009 | Chevrolet Blazer Cars & Trucks

1 Answer

Code PO440 EMC SYSTEM MALFUNCTION what do i look for? on 1999 olds 3.4


CODE PO440 FUEL FILLER CAP IS LOOSE OR CROSS THREAD.CHARCOAL CANISTER IS LOADED WITH FUEL AND MOISTURE.PURGE VALVE VAPOR LINE CLOGGED DAMAGE OR DISCONNECTED.FUEL TANK PRESSURE SENSOR IS DAMAGED DISCONNECTRD OR FAILED.PURGE OR VENT SOLENOID POWER CIRCUIT IS OPEN CHECK THE FUSE.FUEL TANK FUEL FILLER NECK OR FUEL SENDING UNIT O RING IS LEAKING.THIS IS A LIST OF POSSIBLE CAUSE FOR YOUR PROBLEM.

Sep 24, 2009 | 1999 Oldsmobile Alero

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