DTC P0401: EGR System Failure: Testing
NOTE:
EGR solenoid is integral to EGR valve. If EGR solenoid is defective, EGR valve must be replaced.
- Turn ignition on. Using scan tool, read DTCs. If GLOBAL GOOD TRIP counter is displayed and displayed count is "0", go to next step. If GLOBAL GOOD TRIP counter is not displayed or displayed count is not "0", go to step 14.
- Turn off all accessories. Start engine. Allow engine to reach operating temperature. If engine runs rough at idle, go to next step. If engine does not run rough at idle, use scan tool and select ENGINE SYSTEM TEST, then EGR SYSTEM TEST. Select FLOW function. If engine runs rough or stalls, go to next step. If engine does not run rough or stall, go to step 7.
- Turn ignition off. Disconnect EGR solenoid connector. EGR solenoid is integral to EGR valve. EGR valve is mounted to rear of right cylinder head. Start engine. If engine does not run rough or stall, go to next step. If engine runs rough or stalls, remove and inspect EGR tube. Repair or replace EGR tube as necessary. If EGR tube is okay, replace EGR valve.
- Turn ignition off. Disconnect PCM connectors. PCM is located on left side of engine compartment, between Power Distribution Center (PDC) and Transmission Control Module (TCM). See Figure. Inspect connectors for damaged pins, corrosion and loose terminals. Repair connectors as necessary. If connectors are okay, measure resistance between ground and terminal No. 4 (Gray/Yellow wire) at EGR solenoid harness connector. See Fig 1. If resistance 5 ohms or more, go to next step. If resistance is less than 5 ohms, repair short to ground in Gray/Yellow wire between EGR solenoid and PCM.
- Measure resistance between terminals No. 4 (Gray/Yellow wire) and No. 3 (Black/Light Blue wire) at EGR solenoid harness connector. If resistance 5 ohms or more, go to next step. If resistance is less than 5 ohms, Gray/Yellow wire is shorted to Black/Light Blue wire. Repair wiring as necessary.
- At this time, PCM is assumed to be defective. Replace PCM.
- Turn ignition off. Disconnect EGR solenoid connector. EGR solenoid is integral to EGR valve. EGR valve is mounted to rear of right cylinder head. Connect a test light to Orange/Dark Green wire at EGR solenoid harness connector. Turn ignition on. Using test light, probe terminal No. 4 (Gray/Yellow wire) at EGR solenoid harness connector. See Fig 1. Using scan tool, actuate EGR solenoid. If test light flashes on and off, go to next step. If test light does not flash on and off, go to step 10.
- Turn ignition off. Remove and inspect EGR valve and EGR tube for damage, restrictions or leaks. Repair or replace as necessary. If EGR valve and EGR tube are okay, go to next step.
- At this time, PCM is assumed to be defective. Replace PCM.
- Ensure EGR solenoid connector is disconnected. Connect a test light to ground. Using scan tool, actuate Auto Shutdown (ASD) relay. Using test light, probe terminal No. 6 (Orange/Dark Green wire) at EGR solenoid harness connector. If test light illuminates, go to next step. If test light does not illuminate, repair open in Orange/Dark Green wire between EGR solenoid and ASD relay in Power Distribution Center (PDC).
- Measure voltage between ground and terminal No. 4 (Gray/Yellow wire) at EGR solenoid harness connector. If voltage is 4.9 volts or less, go to next step. If voltage is more than 4.9 volts, repair short to voltage in Gray/Yellow wire.
- Turn ignition off. Disconnect PCM connectors. PCM is located on left side of engine compartment, between PDC and Transmission Control Module (TCM). See Figure. Inspect connectors for damaged pins, corrosion and loose terminals. Repair connectors as necessary. If connectors are okay, measure resistance of Gray/Yellow wire between terminals No. 4 at EGR solenoid harness connector and No. 40 at PCM C1 harness connector. See Figure and Fig 1 . If resistance is less than 5 ohms, go to next step. If resistance is 5 ohms or more, repair open in Gray/Yellow wire.
- At this time, PCM is assumed to be defective. Replace PCM.
- Turn ignition off. Visually inspect related connectors and wiring harness for damage. Repair connectors and wiring harness as necessary. If connectors and wiring harness are okay, reconnect all connectors. Test is complete. Check for any related technical service bulletins that may apply.