Diagnostic Aids

An intermittent may be caused by a poor connection, rubbed-through wire insulation or a broken wire inside insulation. Inspect harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, poor terminal-to-wire connection, and damaged harness. Using scan tool, monitor ACTUAL EGR POSITION and wiggle harness and connectors. A change in voltage will indicate area of problem. If DTC cannot be duplicated, check scan tool FAILURE RECORDS to determine mileage since last DTC was set.

1. Perform On-Board Diagnostic (OBD) System Check. See BASIC DIAGNOSTIC PROCEDURES article. Read and record FREEZE FRAME and/or FAIL RECORDS data for each DTC set. Go to next step.
2. Turn ignition on. Review and record scan tool FAILURE RECORDS data. Operate vehicle within FAILURE RECORDS conditions. Using scan tool, monitor SPECIFIC DTC information for DTC P0404 until DTC P0404 test runs. Note result. If scan tool indicates DTC P0404 failed this ignition, go to next step. If scan tool indicates DTC P0404 did not fail this ignition, see DIAGNOSTIC AIDS .
3. Disconnect EGR valve harness connector. Check EGR valve and connector for damaged pins or terminals. Repair as necessary. If connector pins and terminals are okay, go to next step.
4. Remove EGR valve. Check if carbon deposits are present on EGR shaft. If carbon is present, go to next step. If carbon is not present, go to step  6.
5. Clean EGR valve shaft and inside of EGR valve. Check pintle and seat for damage. If damage was present that would effect operation of EGR valve, go to step  7. If no damage was present that would effect operation of EGR valve, go to next step.
6. Reinstall EGR valve. Ensure ignition is off. Install scan tool. Start and run engine at idle. Using scan tool, check EGR operation. If EGR operates correctly, system is okay. If EGR does not operate correctly, go to next step.
7. Replace EGR valve. If DTC P0404 still fails SPECIFIC DTC test on scan tool, replace PCM.