| DTC P1491 (12-3): | EGR Valve Insufficient Lift |
| 1. | Reset the ECM/PCM. |
| 2. | Start the engine. Hold the engine at 3,000 rpm (min-1) with no load (in neutral) until the radiator fan comes on. |
| 3. | Drive the vehicle under load for about 10 minutes. Try to keep the engine speed in the 1,700-2,500 rpm (min-1) range. |
| 4. | Check the Temporary DTC with the scan tool. Is Temporary DTC P1491 indicated? YES - Go to 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/ PCM.n |
| 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 the EGR valve 6P connector terminals No. 4 and No. 6.
Is there battery voltage? YES - Substitute a known-good ECM and recheck. If symptom/indication goes away, replace the original ECM/ PCM.n NO - Go to 9. |
| 9. | Turn the ignition switch OFF. |
| 10. | Turn the ignition switch ON (II). |
| 11. | Measure voltage between the EGR valve 6P connector terminals No. 2 and No. 3.
Is there about 5 V? YES - Go to 13. NO - Go to 12. |
| 12. | Measure voltage between ECM/PCM connector terminals A10 and A20.
Is there about 5 V? YES - Repair open in the wire between the EGR valve and the ECM/PCM (A10, A20).n NO - Substitute a known-good ECM/PCM and recheck. If symptom/indication goes away, replace the original ECM/ PCM.n |
| 13. | Turn the ignition switch OFF. |
| 14. | At the sensor side, measure resistance between the EGR valve 6P connector terminals No. 1 and No. 2.
Is there continuity or resistance of 100 kW or higher? YES - Replace the EGR valve.n NO - Go to 15. |
| 15. | Measure resistance between the EGR valve 6P connector terminals No. 1 and No. 3.
Is there 100 kW or higher? YES - Replace the EGR valve.n NO - Go to 16. |
| 16. | Reconnect the EGR valve connector. |
| 17. | Turn the ignition switch ON (II). |
| 18. | Measure voltage between ECM/PCM connector terminals A10 and A13.
Is there about 1.2 V? YES - Go to 23. NO - Go to 19. |
| 19. | Turn the ignition switch OFF. |
| 20. | Disconnect the negative cable from the battery. |
| 21. | Disconnect ECM/PCM connector A (31P). |
| 22. | Check for continuity between ECM/PCM connector terminal A13 and body ground.
Is there continuity? YES - Repair short in the wire between the EGR valve and the ECM/PCM (A13).n NO - Repair open in the wire between the EGR valve and the ECM/PCM (A13).n |
| 23. | Turn the ignition switch OFF. |
| 24. | Disconnect the EGR valve 6P connector. |
| 25. | Connect the battery positive terminal to the EGR valve 6P connector terminal No. 4.
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| 26. | Start the engine and let it idle, then connect the battery negative terminal to the EGR valve 6P connector terminal No. 6. Does the engine stall or run rough? YES - Go to 27. NO - Replace the EGR valve.n |
| 27. | Turn the ignition switch OFF. |
| 28. | Disconnect the negative cable from the battery. |
| 29. | Disconnect ECM/PCM connector B (24P). |
| 30. | Check for continuity between ECM/PCM connector terminal B14 and body ground.
Is there continuity? YES - Repair short in the wire between the EGR valve and the ECM/PCM (B14).n NO - Go to 31. |
| 31. | Connect the EGR valve 6P connector terminal No. 4 and body ground with a jumper wire.
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| 32. | Check for continulty between ECM/PCM connector terminal B14 and the body ground.
Is there continuity? YES - Go to 33. NO - Repair open in the wire between the EGR valve and the ECM/PCM (B14).n |
| 33. | Disconnect the jumper wire from the EGR valve 6P connector. |
| 34. | Connect the EGR valve 6P connector terminal No. 6 to body ground with a jumper wire.
Is there continuity? YES - Substitute a known-good ECM/PCM and recheck. If symptom/indication goes away, replace the original ECM/ PCM.n NO - Repair open in the wire between the EGR valve and G101.n |