P0400 - EGR Flow Malfunction

The Exhaust Gas Recirculation (EGR) temperature sensor circuit is monitored by the Powertrain Control Module (PCM). During EGR flow the hot exhaust gases heat the EGR temperature sensor. The test fails when the PCM does not detect EGR flow, based on the signal received from the EGR temperature sensor, when conditions call for EGR flow.

Possible Causes:
- EGR valve stuck closed
- EGRC-modulator valve
- EGRC-solenoid valve
- EGR passage
- EGR temperature sensor
- Vacuum hoses
- Exhaust gas leaks

Diagnostic Aids:
The resistance across the EGR temperature sensor at 32°F (0°C) should be between 7.9 and 9.7 M ohms. The resistance across the EGR temperature sensor at 122°F (50°C) should be between 0.57 and 0.7 M ohms.