P1404

Diagnostic Chart:

Wiring Diagram:

CIRCUIT DESCRIPTION

This diagnostic checks for a EGR valve that is stuck open. The VCM determines that the EGR valve is stuck open if the actual EGR position and the learned closed EGR position vary by more than a predetermined value. The VCM checks for a stuck valve when the desired EGR position is at 0%. The VCM commands the EGR valve to 100% during certain driving conditions in order to clear a possible restriction from the EGR valve is the VCM determines that the valve is stuck open. The VCM rechecks for a stuck valve when the desired EGR position returns to 0%. A failure timer is incremented if the stuck EGR valve condition is still present. This DTC sets when the timer reaches a predetermined value.

CONDITIONS FOR SETTING THE DTC

^ The difference between the actual position and the learned position is greater than 0.2 volts.

^ The above condition is present for greater than 10 seconds.

^ The failure counter is greater than five.

ACTION TAKEN WHEN THE DTC SETS

^ The Malfunction Indicator Lamp (MIL) will illuminate.

^ The VCM will record operating conditions at the time the diagnostic fails. The Freeze Frame and Failure Records will store this information.

^ A history DTC is stored

^ The EGR Valve is disabled.

CONDITIONS FOR CLEARING THE MIL/DTC

^ The VCM turns the MIL OFF after 3 consecutive drive trips when the test has Run and Passed and not Failed.

^ A history DTC will clear if no fault conditions have been detected for 40 warm-up cycles (coolant temperature has risen 22°C (40°F) from the startup coolant temperature and the engine coolant temperature exceeds 70°C (160°F) during the same ignition cycle).

^ Use the scan tool Clear Information function.

^ Disconnect the VCM battery feed for 30 seconds.

DIAGNOSTIC AIDS

Due to the moisture associated with exhaust systems, the EGR valve may freeze and stick in colder weather at times. After the vehicle is brought into a warm shop for repairs, the valve warms and the problem disappears. By watching the ACTUAL EGR POSITION and DESIRED EGR POSITION on a cold vehicle with a scan tool, the fault can be verified easily. Check the freeze frame data to determine if the DTC set when the vehicle was cold by viewing the Engine Coolant Temperature (ECT).

TEST DESCRIPTION

Number(s) below refer to the step number(s) on the Diagnostic Table.

2. Commanding the EGR valve open determines whether the EGR system can control the EGR valve accurately and if the malfunction is present.

4. When the EGR valve electrical connector is disconnected, the scan tool should display the Actual EGR Position as 0%. If it does not, the malfunction lies either in the EGR signal circuit or the VCM.

6. If the EGR valve 5.0 volt reference is shorted to voltage, the DMM will read battery voltage and additional DTCs may be set.

11. A poor electrical connection may have caused this DTC to set. Be sure to check the terminals for being backed out, improperly formed, damaged, and for poor tension.

15. The replacement VCM must be programmed and the Crankshaft Position System Variation Learn Procedure must be performed. Refer to the latest Techline procedures for VCM programming.

16. Clearing the DTCs is a very important step for this diagnostic. The clearing function allows the EGR valve to relearn a new minimum pintle position as the old position was inaccurate due to the malfunction that caused the DTC. If the VCM sees an EGR command, the new minimum pintle position will not be learned.

17. If no malfunctions have been found at this point and no additional DTCs were set, refer to the Diagnostic Aids for additional checks and information.