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DTC P0400 (EGR): EGR Flow Malfunction

WARNING: Use extreme caution when checking EGR valve. Valve will be extremely hot and can cause severe burns.
  1. If vehicle is equipped with automatic transmission, go to next step. If vehicle is equipped with 2.2L and manual transmission, check A/T-M/T identification circuit. Turn ignition on. Using DVOM connected to chassis ground, backprobe ECM connector terminal No. 81. See appropriate wiring diagram in WIRING DIAGRAMS article. If voltage is 2 volts or more, repair wiring and/or connector. If voltage is less than 2 volts, check ECM connector contacts. If contacts are okay, replace ECM with known good unit and retest.
  2. Connect SSM. Retrieve DTC(s). If DTC P0106 , P0107, P0108, P0403, P1102, P1122 or P1421 exist, diagnose affected DTC(s) first. If other codes exist, manually check EGR valve diaphragm for sticking. After checking, go to CONFIRMATION OF ACTUAL DRIVING PATTERN at end of this test, clear DTC(s) and retest. If DTC P0400 only exists, go to next step.
  3. Check all EGR vacuum hoses for leaks, cracks, clogging or other damage. Check and repair as necessary:
    • Pipes and hoses running between throttle body and Backpressure Transducer (BPT)
    • Pipe and hose line connecting BPT and EGR solenoid valve
    • Hose between EGR solenoid valve and EGR valve
    • BPT pressure hose

    After checking and repairing, go to CONFIRMATION OF ACTUAL DRIVING PATTERN . If no problems are found, go to next step.

  4. Turn ignition off. Connect SSM. Set SSM to function mode FD05, to check EGR solenoid operation. EGR solenoid can also be checked by disconnecting EGR solenoid valve connector, then connecting an external 12-volt source (not tested vehicle's battery) to EGR solenoid valve. Start engine. Open throttle valve 5-10 degrees and visually check EGR valve operation. If EGR valve operates, malfunction may be due to freezing or clogging by foreign matter. DO NOT  replace EGR valve at this point since it may not be faulty. Proceed to CONFIRMATION OF ACTUAL DRIVING PATTERN . If malfunction is again detected in CONFIRMATION OF ACTUAL DRIVING PATTERN check for clogging in gas outlets of intake manifold or cylinder head (check by blowing into outlets). If clogged, repair or replace intake manifold or cylinder head and return to CONFIRMATION OF ACTUAL DRIVING PATTERN . If not clogged, replace EGR valve and go to CONFIRMATION OF ACTUAL DRIVING PATTERN.
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