P1491
DTC P1491: EGR Valve Insufficient Lift1. Reset the ECM.
2. Start the engine. Hold the engine at 3,000 rpm with no load (in Park or neutral) until the radiator fan comes on.
3. Check the Temporary DTC with the scan tool.
4. Drive the vehicle under load for about 10 minutes. Try to keep the engine speed in the 1,500 - 2,500 rpm range.
Is Temporary DTC P1491 indicated?
YES - Go to step 5.
NO - Intermittent failure, system is OK at this time. Check for poor connections or loose wires at the EGR valve and at the ECM.
5. Turn the ignition switch OFF.
6. Disconnect the EGR valve 6P connector.
7. Start the engine and let it idle.
8. Measure voltage between EGR valve 6P connector terminals No.4 and No.6.
Is there battery voltage?
YES - Update the ECM if it does not have the latest software, or substitute a known-good ECM, then recheck. If the symptom/indication goes away with a known-good ECM, replace the original ECM.
NO - Go to step 9.
9. Turn the ignition switch OFF.
10. Turn the ignition switch ON (II).
11. Measure voltage between EGR valve 6P connector terminals No.2 and No.3.
Is there about 5 V?
YES - Go to step 13.
NO - Go to step 12.
12. Measure voltage between ECM connector terminals C18 and C28.
Is there about 5 V?
YES - Repair open in the wire between the EGR valve and the ECM (C18).
NO - Update the ECM if it does not have the latest software, or substitute a known-good ECM, then recheck. If the symptom/indication goes away with a known-good ECM, replace the original ECM.
13. Turn the ignition switch OFF.
14. At the sensor side, measure resistance between EGR valve 6P connector terminals No.1 and No.2.
Is there continuity or resistance of 100 kOhms or higher?
YES - Replace the EGR valve.
NO - Go to step 15.
15. Measure resistance between EGR valve 6P connector terminals No.1 and No.3.
Is there 100 kOhms or higher?
YES - Replace the EGR valve.
NO - Go to step 16.
16. Reconnect the EGR valve connector.
17. Turn the ignition switch ON (II).
18. Measure voltage between ECM connector terminals C6 and C18.
Is there about 1.2 V?
YES - Go to step 21.
NO - Go to step 19.
19. Turn the ignition switch OFF.
20. Check for continuity between ECM connector terminal C6 and body ground.
Is there continuity?
YES - Repair short in the wire between the EGR valve and the ECM (C6).
NO - Repair open in the wire between the EGR valve and the ECM (C6).
21. Turn the ignition switch OFF.
22. Disconnect the EGR valve 6P connector.
23. Connect the battery positive terminal to EGR valve 6P connector terminal No.4 with a jumper wire.
24. Start the engine and let it idle, then connect the battery negative terminal to EGR valve 6P connector terminal No.6 with a jumper wire.
Does the engine stall or run rough?
YES - Go to step 25.
NO - Replace the EGR valve.
25. Turn the ignition switch OFF.
26. Disconnect ECM connector B (25P).
27. Check for continuity between ECM connector terminal B7 and body ground.
Is there continuity?
YES - Repair short in the wire between the EGR valve and the ECM (B7).
NO - Go to step 28.
28. Connect EGR valve 6P connector terminal No.4 and body ground with a jumper wire.
29. Check for continuity between ECM connector terminal B7 and body ground.
Is there continuity?
YES - Go to step 30.
NO - Repair open in the wire between the EGR valve and the ECM (B7).
30. Check for continuity between EGR valve 6P connector terminal No.6 and body ground.
Is there continuity?
YES - Update the ECM if it does not have the latest software, or substitute a known-good ECM, then recheck. If the symptom/indication goes away with a known-good ECM, replace the original ECM.
NO - Repair open in the wire between the EGR valve and G101.