Question about 1999 Pontiac Firebird

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Cooling fans wont come on

I replaced all 3 relays & ect sensor didnt fix the problem. When ect is not plugged in fans come on what do i do next?

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  • Pontiac Master
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I think you may have a PCM problem, the fact the fans come on in "failure mode" when the ECT signal is lost indicates the circuits to the fans are ok. Technicians disconnect the ECT to verify fan operation as a quick test for checking the fan circuit and the fan motors. one last note, you do realize the fans don't come on until either the AC is on or the engine reaches approx 235 Degrees F. at idle that takes a long time.

Posted on Aug 21, 2008

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Need a wiring diagram of the 2 wires from the temp sending unit that controls the temp gauge and cooling fans on a 99 grand am gt. Need to see where they go They disappear behind the engine


The PCM regulates voltage to the coolant fan relays, which operate the fans. Refer to Engine Controls.

Engine Cooling Fan Description - Electric
The electric cooling fans are used to lower the temperature of the engine coolant flowing through the radiator. They are also used to cool the refrigerant (R-134a) flowing through the A/C condenser.
Operation
The electric cooling fan operates when the engine cooling temperature exceeds a certain value. The cooling fan on this engine is controlled by the PCM. The cooling fan has one speed. The PCM turns the cooling fan ON by grounding the coil of the cooling fan relay when certain conditions are met. When the A/C is requested, the cooling fan will also be turned ON.
Power for the cooling fan motors are supplied through Cool Fan #1 and Cool Fan #2 relays. The cooling fan relays are energized when current flows from the fuses in the Cell 23: Cooling Fan Controls , and through the relay coils to ground through the PCM. The Low Speed fans control circuit is grounded for low speed fans operation. During low speed fans operation, both fans run at a slow speed. The High Speed fans control circuit is grounded for high speed operation. During high speed fans operation, both fans run at high speed.
Important: When certain Diagnostic Trouble Codes (DTCs) are present, the PCM may command the cooling fans to run all the time. It is important to perform Powertrain On Board Diagnostic (OBD) System Check prior to diagnosing the engine cooling fans.
If a problem that involves the low speed cooling fan relay control circuit exists, DTC P0480 should set. If the problem affects the high speed cooling fan relay control circuit, DTC P0481 should set. A problem with the ECT sensor should set DTC P0117, P0118, P1114, or P1115. Any of these DTCs will affect cooling fan operation and should be diagnosed before using the Cooling Fan Diagnosis tables. The Cooling Fan Diagnosis tables should be used to diagnose the PCM controlled cooling fans only, if a DTC has not set.

The engine coolant temperature (ECT) sensor (3) is a thermistor, a resistor which changes value based on temperature, mounted in the engine coolant stream. Low coolant temperature produces a high resistance (100,000 ohms at -40°C) (-40°F), while high temperature causes low resistance (70 ohms at 130°C) (266°F).
The PCM supplies a 5 volt signal to the ECT sensor through a resistor in the PCM and monitors the terminal voltage. Since this forms a series circuit to ground through the ECT sensor, high sensor resistance (low temperature) will result in high PCM terminal voltage. When the resistance of the ECT sensor is low (high temperature), the terminal voltage will be drawn lower. This terminal voltage indicates engine coolant temperature to the PCM.
A hard fault in the ECT sensor circuit should set either a DTC P0117 or P0118. Remember, these DTCs indicate a malfunction in the engine coolant temperature circuit, so proper use of the DTC table may lead to either repairing a wiring problem or replacing the sensor, to properly repair a problem.

The engine coolant sensor is an input to the PCM , Two wire's both go to the PCM .An the PCM turns on the cooling fans !

DTC P0480 Cooling Fan Relay 1 Control Circuit
DTC P0481Cooling Fan Relay 2 Control Circuit
The Body Control Module (BCM) request the cooling fans. The BCM sends a Class 2 message to the PCM in order to enable the fans based on various inputs. Thebattery voltage travels to all three cooling fan relay coils. The PCM enables cooling fan relay #1 by providing the ground path. The PCM enables cooling fan relays #2 and mode control together by providing a ground path. The left and right cooling fans are connected in series. This will enable both fans on low speed when the fan #1 relay is energized. When all three fan relays are energized, both fans will operate at high speed. The high speed is possible because the fan relays are wired in a parallel circuit. When the PCM detects that certain DTCs are set, the PCM will enable the cooling fans.
The PCM will enable the engine cooling fans when certain Diagnostic Trouble Codes are set.

Important: A short to ground will cause an open fuse(s). Before performing this diagnostic procedure, inspect the fuse(s) for an open.
1
Did you perform the Instrument Cluster System Check?
--
Go to Step 2
Go to Instrument Cluster System Check
2
Turn the ignition switch to the ON position.
With the scan tool select Instrument Panel Cluster, Special Functions, Instrument Panel Cluster (IPC) gauges.
Perform the Coolant Gauge Sweep Test.
Does the coolant temperature gauge complete a full sweep when commanded?
--
Go to Powertrain On Board Diagnostic (OBD) System Check in Engine Controls
Go to Step 3
3
Replace the instrument cluster. Refer to Instrument Cluster Replacement .
Did you complete the repair?
--
Go to Instrument Cluster System Check
--

Your best bet would be to take your vehicle to a qualified repair shop that knows how the system works . An has the tools to diagnose the problem .

Nov 13, 2016 | 1999 Pontiac Grand Am GT

2 Answers

FANS WONT COME ON ,,ALL FUSES,RELAYS AND ELECTRIC FAN MOTORS ARE NEW,,THERMOSTAT IS GOOD,,WHERE IS ELECTRIC FAN TEMP SENSOR LOCATION


op
why not post symptoms first and not a barrage of parts.
must we decode that to a symptom,. kinda hard right.

I will not guess. what is wrong, nor what is not working on your car. now what fans you are talking about, up to 4 fans on cars.

cab blower fan (wild guess blower is ok) and so is HVAC, ?
radiator fans
Condenser fan.

my wild guess to , engine over heats?????????
if yes, the scan it first. no not last FIRST.
it dont work like you think its not a 1988 Samurai.
sorry,
on modern cars, they got smarter, the engine goes
gee the PCM knows water temp why have a fan temp regulator.
hark , now it dont. (saves cash on useless parts)
but has a relay , (well until you have my car and the relay is now 100% electronic, called a huge transistor)
we've used this tech in industry for years, but car makers just learning how still.
i digress. but evolution and history helps diagnosis.
what is there?

Ill look for you, ive posted this 100s of times
the book is 4 bucks to see online. the real deal
lets look now.
XL-7 (the dash matters big time)
answering for , overheats engine, and fans on RAD dead.
(some are staged, PCM brains... now. and also chain ops based on if A/C is on or not) facts.
first I see 2 fans... ok.
the next page shows nice block diagram of the fan system
yup, NOT Simple.

ill post those words for you.
"The engine cooling fan system consists of 2 electrical cooling fans and 3 fan relays. The relays are arranged in a series/parallel configuration that allows the engine control module (ECM) to operate both fans together at low or high speeds. The cooling fans receive positive voltage from the cooling fan relays which receive battery positive voltage from the underhood fuse block.
During low speed operation, the ECM supplies the ground path for the low speed cooling fan relay which is fan 1 relay through the low speed cooling fan relay control circuit. This energizes the low speed fan relay coil, closes the relay contacts, and supplies battery positive voltage from the fan 1 fuse through the cooling fan motor supply voltage circuit to the left cooling fan. The ground path for the left cooling fan is through the series/parallel relay which is fan 2 relay, and the right cooling fan. The result is a series circuit with both fans running at low speed.
During high speed operation the ECM supplies the ground path for the low speed fan relay through the low speed cooling fan relay control circuit. The ECM grounds the high speed fan relay, which is fan 3 relay, and the series/parallel relay, which is fan 2 relay through the high speed cooling fan relay control circuit. This energizes the series/parallel relay coil, closes the relay contacts, and provides a ground path for the left cooling fan. At the same time the high speed fan relay coil is energized closing the relay contacts and provides battery positive voltage from the fan 2 fuse 1 on the cooling fan motor supply voltage circuit to the right cooling fan. During high speed fan operation, both engine cooling fans have their own ground path. The result is a parallel circuit with both fans running at high speed.
When the request for fan activation is withdrawn, the fan may not turn OFF until the ignition switch is moved to the OFF position or the vehicle speed exceeds approximately 16 km/h (10 mph). This is to prevent a fan from cycling ON and OFF excessively at idle.
end quote.

i bet you didnt scan it , like 99.9 % of all posters here dont.
DTC Descriptors
DTC P0480: Cooling Fan Relay 1 Control Circuit
DTC P0481: Cooling Fan Relay 2 Control Circuit
DTC P0691: Cooling Fan Relay 1 Control Circuit Low Voltage
DTC P0692: Cooling Fan Relay 1 Control Circuit High Voltage
DTC P0693: Cooling Fan Relay 2 Control Circuit Low Voltage
DTC P0694: Cooling Fan Relay 2 Control Circuit High Voltage
Diagnostic Fault Information

is the ECT showing overheat, yes no?
if yes, it must operate a fan or 2.
the book even covers all tests for fans dead, in a large truth table.
both the FSM and alldata.com have that, its no secret ,its published in 4 major places.

lets back up
if the engine coolant is low (no that side tank the engine and rad)
the ECT will lie. if that happens the fans may not come one
that is because the ECT is useless measuring air, for water.
that water must touch ECT for ECT to work.
this is FIRST
then scan the ECT does it show overheating, IT must if it IS overheating. fix that next if it lies to you,(IR gun in hand)

The system has staged fans.
i cant find the trip points in my crappyy online pages.
but is like 225f then 250f trips. is my guess...
about. if the engine over heats, check fuses first then scan it.
it will simply tell you why its bad.
eg, fan1 output dead.
or if you hot wire a fan and its dead, then it is.
(only on cars with non modulated fans,,hot wire them,else not.)

now the link to the 4 buck real book.
the non dash XL7 (my guess) you this pick yourself... cant see car.
https://suzukipitstopplus.com/Products/10182-2007-xl7-service-manual.aspx

this is how it really works
the ECU has software that decide trip points for fans.
hard coded, this is. based on how hot it is and if A/C is on not.
its way smarter than 1988 and better.
the DTC errors can see an open line, shorted to ground or stuck 12v.(runs all time error)
(tells you relay is good or not)

25839272-0kjd5huq4lpr130nt243wle5-3-0.jpg no scanner no joy , sorry, tis a fact.....

25839272-0kjd5huq4lpr130nt243wle5-3-2.jpg

Aug 27, 2015 | 2007 Suzuki XL-7

1 Answer

Location of radiator fan relay 1992 ford tempo gl


The radiator cooling fan relay in ford Tempo gl has been integrated into the CCRM (Constant Control Relay Module) this is the black box fixed to the left strut tower with the big cable harness on it.

This relay box is commanded by the PCM (Powertrain Control Module) it´s linked to every sensor in the car. (It's located behind the fuse panel next to the steering column.

The PCM supervises various conditions, including the signal that the ECT (Engine Coolant Temperature) sensor sends and power up the Fan Relay into CCRM to activate the Cooling Fan.
-------------
This should help.Thanks.Helpmech.

Mar 01, 2011 | 1992 Ford Tempo

2 Answers

Electric Radiator Fan Does Not Come On


Chevy dealer says will not come on until temperature reaches 219 f

May 16, 2010 | 2007 Chevrolet Silverado 1500 2WD

1 Answer

Where is the switch that cuts on the cooling fans on a 2000 grand am with a 3.4 engine


The computer turns on the fan. Based on sensors from the motor.
DTC P0480 - COOLING FAN CIRCUIT

Circuit Description

The cooling fan is controlled by PCM through the fan relay based on inputs from ECT sensor, IAT sensor, A/C selector switch, A/C refrigerant pressure switch and vehicle speed sensor. PCM controls cooling fan by grounding cooling fan control circuit which turns on cooling fan relay.

The fan relay will be commanded on when ECT reaches 223°F (106°C) or greater, A/C is requested or vehicle speed is less than 38 MPH. Cooling fan relay will also be commanded on regardless of vehicle speed when a DTC is set requesting cooling fan to be on, ECT is 304°F (151°C) or greater, or A/C refrigerant pressure is high. Cooling fan may also be commanded on when engine is not running, on certain conditions.

Conditions for setting DTC:

Battery voltage greater than 9.5 volts.

Cooling fan fault line detects a malfunction for 6 seconds.

1. Check cooling system. Ensure coolant level and belt tension are correct. Adjust/repair as necessary. After repairs, go to step 23). If no adjustment or repairs were required, go to next step.

2. Turn ignition on, with engine off. Using scan tool, check if cooling fan is operating with ECT at less than 209°F (98°C). If cooling fan is off, go to next step. If cooling fan is on, go to step 4).

3. Command cooling fan relay on. If cooling fan operates, go to step 23). If cooling fan does not operate, go to step 5).

4. Turn ignition off. Disconnect PCM harness connector. If cooling fan turns off, go to step 23). If cooling fan does not turn off, go to step 6).

5. Disconnect cooling fan relay harness connector. Using a test light connected to ground, probe battery feed circuits in relay harness connector. If test light illuminates on both terminals, go to step 7). If test light does not illuminate on both terminals, go to step icon_cool.gif.

6. Disconnect cooling fan relay harness connector. With test light connected to ground, probe battery feed circuit in relay harness connector. If test light illuminates, go to step 9). If test light does not illuminate, go to step 10).

7. Connect a jumper wire between cooling fan relay battery feed and cooling fan battery feed circuit. If cooling fan operates, go to step 11). If cooling fan does not operate, go to step 12).

8. Repair open in battery feed circuit. After repairs, go to step 23).

9. Repair short to voltage in cooling fan battery feed circuit. After repairs, go to step 23).

10. Connect test light battery voltage and probe cooling fan control circuit. If test light illuminates, go to step 13). If test light does not illuminate, go to step 21).

11. Connect test light to battery voltage and probe cooling fan control circuit. Using scan tool, command cooling fan on. If test light illuminates, go to step 14). If test light does not illuminate, go to step 15).

12. With jumper wire still connected, disconnect cooling fan harness connector. Using test light connected to ground, probe cooling fan battery feed circuit. If test light illuminates, go to step 16). If test light does not illuminate, go to step 17).

13. Repair short to ground in cooling fan control circuit. After repairs, go to step 23).

14. Check terminals to cooling fan relay. Repair as necessary. After repairs, go to step 23). If terminals are okay, go to step 21).

15. Check cooling fan control circuit for open or poor connection. Repair as necessary. After repairs, go to step 23). If circuit or connection is okay, go to step 22).

16. Connect test light to battery voltage and probe cooling fan ground circuit. If test light illuminates, go to step 1icon_cool.gif. If test light does not illuminate, go to step 19).

17. Repair open or poor connection in cooling fan ignition feed circuit. After repairs, go to step 23).

18. Check for poor connections at cooling fan harness connector. Repair as necessary. After repairs, go to step 23). If connections are okay, go to step 20).

19. Repair open or poor connection in cooling fan ground circuit. After repairs, go to step 23).

20. Replace cooling fan motor. After replacing cooling and motor, go step 23).

21. Replace cooling fan relay. After replacing relay, go to step 23).

22. Replace PCM. Program replacement PCM using required equipment. After replacing PCM, go to next step.

23. Turn ignition on, with engine off. Command cooling fan on. If cooling fan operates, system is okay. If cooling fan does not operate, repeat step 1).

May 16, 2010 | 2000 Pontiac Grand Am GT

1 Answer

06 vue cooling fan wont shut off tried new relay swich and the 40a fuse is obviously good. what could it be, temp sending unit?


The power for the fan comes from 2 relays in the
junction block on the left fender. One is a high fan relay 40amp the other is the low fan relay 20amp.
If either one is stuck, it will power the fan. Also if the
engine coolant temp(ect)sensor is bad, it can send a
false signal to the engine control module(ecm) and powering the fan. With the engine cool, if the fans still
running. Unplug the ect sensor(on thermo. housing)
if the fan stops replace the sensor. If not pull the relays one at a time. And see which one stops the fan. If none of this works it may be an ecm problem.
Hope this helps.

Mar 21, 2010 | 2005 Saturn VUE

3 Answers

2005 chrysler 300c 5.7l v8 hemi.........over heating electric fans do not come on......however when fans are checked individually they work....the two fuses and the 3 relays check ok......made check with...


The fans are turned on by the PCM, if the PCM is not telling the fans to turn on, they won't even if everything tests fine.

2005 Chrysler 300 V8-5.7L VIN H

Coolant Temperature Sensor/Switch (For Computer): Service and Repair
ENGINE COOLANT TEMP SENSOR
REMOVAL
The Engine Coolant Temperature (ECT) sensor (3) on the 5.7L engine is located under the air conditioning compressor. It is installed into a water jacket at the front of the cylinder block.
WARNING: HOT, PRESSURIZED COOLANT CAN CAUSE INJURY BY SCALDING. COOLING SYSTEM MUST BE
PARTIALLY DRAINED BEFORE REMOVING THE COOLANT TEMPERATURE SENSOR.
1. Partially drain the cooling system.
2. Remove accessory drive belt.
3. Carefully unbolt air conditioning compressor from front of engine. Do not disconnect any A/C hoses from compressor. Temporarily support
compressor to gain access to ECT sensor (3).
4. Disconnect electrical connector (2) from sensor (3).
5. Remove sensor (3) from cylinder block.
INSTALLATION
1. Apply thread sealant to sensor threads.
2. Install ECT sensor (3) to engine.
3. Tighten sensor to 11 Nm (97.3 inch lbs.) torque.
4. Connect electrical connector (2) to ECT sensor (3).
5. Fill the cooling system.

Sep 10, 2009 | 2005 Chrysler 300

2 Answers

Cooling fans dont engage! 1998 oldsmobile silhouette!


Your Problem Can VERY WELL BE with the Temp Sensor, As It Is the First in This Electrucal Circut . it Waits for 210-230 Degree Engine temp and Gives that Sygnal to the ECM then ECM Grounds out the Cooling FAN RELAY To Turn ON the FANS and the Temp Sensor is Usualy THE #1 Culpret Closley in front of the RELAY.
There are 2 Sensors On this Vehicle The One You Replaced and One Located At Trans Side of
Engine Closer to Front of Vehicle At the Head ,Thereis a 2 wire Plug On it and This Sensor Goes to the ECT witch CONTROLS COOLING FAN RELAY. Hope this Helps and if you Need A Diagram For this It Must be Emailed as FixYa Does NOT Support Large Picture Files. My Email Add. Is MY
Screen Name Here on FixYa @aol.com

Jun 15, 2009 | 1998 Oldsmobile Silhouette

1 Answer

I want to know where the Coolant Temp sensor is on a 04 2.4 PT


the engine coolant temp sensor is in the assembly that the pressure cap (radiator cap) goes on. it's under the part that the cap goes on, closer to the engine block. you can see the wires and the plug going to it. here's the remove and replace step by step:
1. disconnect battery negative terminal (they always tell you to do that when you work on electrical parts)
2.partially drain cooling system below level of ect sensor
3.disconnect ect sensor
4.remove ect sensor
and to reinstall
1.install ect sensor torque to 168 in-lbs
2.connect sensor electrical connector
3.connect battery negative terminal
4.refill system with coolant
hope that helps

Jun 03, 2009 | 2004 Chrysler PT Cruiser

3 Answers

Van chevrolet venture 2000


Fifteen minutes! you have bigger problems than only the fans the fans are controlled by a thermo switch that is heated by the coolant, If you have no coolant the sensor cannot activate But fifteen minutes seems like you may have a headgasket problem and steam cannot heat the coolant sensor.OperationNotesThe electric cooling fan operates when the engine cooling temperature exceeds a certain value. The cooling fan on this engine is controlled by the Powertrain Control Module (PCM) . The PCM turns the cooling fan ON by grounding the coil of the cooling fan relays when certain conditions are met. When the A/C is requested, the cooling fan will also be turned ON.

Power for the cooling fan motors are supplied through Maxifuses(R). The cooling fan relays are energized when current flows from the fuses in the Underhood Accessory Wiring Junction Block, and through the relay coils to ground through the PCM. The Coolant Fan 1 Relay Control Circuit is grounded for low speed fans operation. During low speed fans operation, both fans run at a slow speed. The Coolant Fan 1 Relay Control Circuit is grounded for high speed operation. During high speed fans operation, both fans run at high speed.

IMPORTANT: When certain Diagnostic Trouble Codes (DTCs) are present, the PCM may command the cooling fans to run all the time. Perform the A Powertrain On Board Diagnostic (OBD) System Check prior to diagnosing the engine cooling fans.

For more information regarding the Charging System, refer to Charging System Description , and Charging System Circuit Description in Starting and Charging.

If a problem that involves the low speed cooling fan relay control circuit exists, DTC P0480 Cooling Fan Relay 1 Control Circuit should set. If the problem affects the high speed cooling fan relay control circuit, DTC P0481 Cooling Fan Relay 2 Control Circuit should set. A problem with the ECT sensor should set DTC P0117 Engine Coolant Temperature (ECT) Sensor Circuit Low Voltage, DTC P0118 Engine Coolant Temperature (ECT) Sensor Circuit High Voltage, DTC P1114 Engine Coolant Temperature (ECT) Sensor Circuit Intermittent Low Voltage, DTC P1115 Engine Coolant Temperature (ECT) Sensor Circuit Intermittent High Voltage. Any of these DTCs will affect cooling fan operation and should be diagnosed before using the Electric Cooling Fan Diagnosis.

For more information regarding the Cooling System refer to Engine Cooling Fan Description - Electric, and Cooling System Description in Cooling System.


Here is the electrical schematic and how it all is suppose to work,
If you need any further help please contact me Thank you,Randy If you find this information helpful please give me a good rating

www.aceautomotive1.com

Aug 16, 2008 | 2000 Chevrolet Venture

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