Diagnostic test shows EGR valve excessive flow. One shop installed 2 new sensors ($285), said EGR valve ok, wiring/hoses ok. Light still on. They couldn't solve, said go to dealer. Ford Dealer diagnostic test ($100). Insisted EGR valve no good. Installed new EGR valve ($160), said wiring/hoses ok, computer ok. Service engine light still came on. Ford dealer examined car again. Now saying "computer no good", saying computer costs $500. Said need new computer because they show a "spiking" at the egr valve when testing. Have already paid $545.00 for parts and labor and light still on. Afraid to spend another $500 for a new computer cause their explanation why need new computer sounds like just guessing and not really sure. What shall I do?
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Re: Service Engine Soon
A couple of things you can try:
remove the negative battery terminal to reset your car's computer. There are some car stereos that would require a security code when the battery is removed;
on your next fill up, try if you can get a higher octane gas instead of your normal, say if you use to put in 91, shift temporarily to 95;
add a can of injector/carb cleaner in your gas tank;
on a long stretch, drive aggressively and hard. The idea is to clean your fuel system, combustion chamber, valves, exhaust manifold, catalytic converter, exhaust system including your EGR and O2 sensors.
If error indicator persist, trace the EGR wiring with special attention to the connectors at the ends.
Hope this be of initial help/idea. Pls post back how things turned up or should you need additional information.
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P1121 Ford Throttle Position Sensor Inconsistent with Mass Air Flow Sensor http://engine-codes.com/p0401_ford.html no they are not related !
Are there any cracks in the rubber hose from air cleaner to throttle body ! That could cause the P1121 air entering after mass air flow sensor !
P1121 - Throttle Position (TP) Sensor Inconsistent with MAF Sensor
The PCM monitors a vehicle operation rationality check by comparing sensed throttle position to mass air flow readings. If during key ON engine running self-test the comparison of the TP sensor and MAF sensor readings are not consistent with calibrated load values, the test fails and a diagnostic trouble code is stored in continuous memory.
Air leak between MAF sensor and throttle body
TP sensor not seated properly
Damaged TP sensor
Damaged MAF sensor
Drive vehicle and exercise throttle and TP sensor in all gears. A TP PID (TP V PID) less than 4.82 % (0.24 volt) with a LOAD PID greater than 55% or a TP V PID greater than 49.05% (2.44 volts) with a LOAD PID less than 30% indicates a hard fault.
P0401 - EGR Flow Insufficient Detected
The EGR system is monitored during steady state driving conditions while the EGR is commanded on. The test fails when the signal from the DPF EGR sensor indicates that EGR flow is less than the desired minimum.
EGR valve stuck closed
EGR valve leaks vacuum
EGR flow path restricted
EGRVR circuit shorted to PWR
VREF open to D.P.F. EGR sensor
D.P.F. EGR sensor downstream hose off or plugged
EGRVR circuit open to PCM
VPWR open to EGRVR solenoid
D.P.F. EGR sensor hoses both off
D.P.F. EGR sensor hoses reversed
Damaged EGR orifice tube
Damaged EGRVR solenoid
Perform KOER self-test and look for DTC P1408 as an indication of a hard fault. If P1408 is not present, look for contamination, restrictions, leaks, and intermittents
a vacuum restriction to the map sensor--a skewed map sensor reading can cause the PCM to read an incorrect MAP change during the EGR flow test
an engine that is running poorly due to mechanical condition such as worn piston rings, ect. can cause low engine vacuum thus EGR flow test will fail
excessif backpressure of the exhaust system can cause P0401
exhaust system leak can cause an insufficient amount of EGR flow
a restriction in the intake manifold such as carbon deposit and casting flash.
po300 random misfire po401 low flow egr p1404 egr. check spark plugs and check for vacume leaks. with the po400 1404 could be your egr valve is good but po400 means low flow which to me indicates that the egr passage may be clogged up and needs to be cleaned out check out scottykillmer.com the passage way may be easy to clean depending on the position of the egr vavle but you might have to remove the intake manifolld
This is not a cut and dry fault code. This means that more than one thing wrong can set the code in the computers memory. Here is the low down on the P0402 fault code. This is from the OBD2 fault code diagnostic book.
P0402 - Exhaust Gas Recirculation Flow Excessive Detected
- Engine Light ON (or Service Engine Soon Warning Light) - Possible engine hesitation
- EGR solenoid valve harness is open or shorted - EGR solenoid valve circuit poor electrical connection - EGR volume control valve stuck closed - Dead (Weak) battery - Faulty EGR temperature sensor and circuit - Faulty EGR Valve - EGR passage clogged - Exhaust gas leaks
Exhaust Gas Recirculation (EGR) System
The exhaust gas recirculation (EGR) system is designed to:
reintroduce exhaust gas into the combustion cycle.
lower combustion temperatures.
reduce the formation of oxides or nitrogen (NOX).
The amount of exhaust gas reintroduced and the timing of the cycle varies by calibration. Timing and volume are controlled by the following:
exhaust system back pressure
engine coolant temperature
air charge temperature
The EGR valve (EGR valve) (9D475) is vacuum-actuated. The vacuum hose routing diagram is shown on the Vehicle Emission Control Information (VECI) decal.
The EGR system is a differential pressure feedback EGR Sensor system. Differential pressure feedback EGR Sensor is a subsonic closed loop EGR system. The differential pressure feedback EGR system:
monitors EGR flow rate by the pressure drop across the metering orifice located in the EGR tube.
uses a differential pressure feedback EGR sensor as the feedback device.
uses the EGR valve only as a pressure regulator, rather than a flow metering device.
controlled pressure is varied by the valve movement using vacuum output of the EGR vacuum regulator solenoid (9J459).
allows for a more accurate assessment of EGR flow requirements.
Differential Pressure Feedback EGR Flow Diagram
Differential Pressure Feedback EGR Sensor
Disconnect engine control sensor wiring (12A581) from Differential Pressure Feedback EGR Sensor.
Disconnect Differential Pressure Feedback EGR Sensor hoses from EGR valve to exhaust manifold tube (9D477).
Remove retaining nuts or bolts (depending upon application) and EGR Differential Pressure Feedback transducer.
Follow removal procedure in reverse order.
Tighten retaining nuts or bolts (depending upon application) to 5-7 Nm (45-61 lb-in).
Based on what the tech manuals say I would change the DPFE sensor for the EGR Valve, careful not to tear the special silicone rubber hoses that go to it from the exhaust, as a Ford dealer tech I saw these codes allot, and the DPFE sensor was almost always the issue or the hoses going to it.