DTC P0400 (EGR) - EGR Flow Malfunction: Notes

Connect SSM. Retrieve DTC(s). Check if DTC P0105, P0106, P0403 or P1102 is present. If DTC(s) is present, diagnose affected DTC(s) first. Manually check EGR valve diaphragm for sticking. After checking, go to CONFIRMATION OF ACTUAL DRIVING PATTERN, clear DTCs and retest. If DTC(s) does not reset, go to next step.
WARNING: Use extreme caution when checking EGR valve. Valve will be extremely hot and can cause severe burns.
Check 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 leakage is not found, go to next step.
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 harness connector, then connecting an external 12-volt source to EGR solenoid valve.
CAUTION: DO NOT use vehicle battery as 12-volt source. Vehicle electrical system may be damaged.

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. Go 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 breathing 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.