DTC P0400: EGR Function
- Check Vacuum Source To EGR Valve - Start engine and allow it to warm up. Set engine speed between 2000-4000 RPM. Disconnect hose to EGR valve and check for vacuum. If vacuum exists, go to next step. If vacuum does not exists, check vacuum hoses for restrictions, misrouting, cracks or improper connection. If not faults are found, go to next step.
- Check EGRC Solenoid - Turn ignition on. Check operating sound of EGRC solenoid while disconnecting and reconnecting EGRC solenoid harness connector. If solenoid is not functioning properly, repair or replace solenoid as required. If solenoid is functioning properly, go to next step.
- Disconnect EGRC solenoid. Apply battery voltage and ground to terminals No. 1 and 2. See Figure. With battery voltage applied, air should pass between ports "A" and "B". Air should not pass between ports "A" and "C". With no voltage applied, air should pass between ports "A" and "C". Air should not pass between ports "A" and "B". Replace EGRC solenoid if airflow is not as specified. If solenoid is okay, check vacuum hoses for restrictions or misrouting.
- - Check EGR Temperature Sensor
- Ensure sensor is not damaged or contaminated. Check ECM and EGR temperature sensor harness connectors for damage, corrosion or pushed-out pins. Repair if necessary. If no problems are found, ensure ignition is off. Measure resistance between EGR temperature sensor connector terminals as follows:
- With temperature at 32°F (0°C), resistance should be 7.9-9.7 megohms.
- With temperature at 122°F (50°C), resistance should be .57-.70 megohms.
- With temperature at 212°F (100°C), resistance should be .08-.10 megohms.
If resistance is not as specified, replace EGR temperature sensor. If resistance is as specified, disconnect harness connectors in circuit and check for damage or corrosion. If fault is still present, go to DTC P0402: EGR CONTROL BACKPRESSURE TRANSDUCER (EGRC-BPT) VALVE.