A/T Model
DTC P1491: Malfunction in EGR System - A/T Model1. Reset the PCM.
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 for a Temporary DTC with the scan tool.
4. Drive the vehicle under load for about 10 minutes. Try to keep the engine speed in the 1,700 - 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 PCM.
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 - Substitute a known-good PCM, and recheck. If the symptom/indication goes away, replace the original PCM.
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 approx. 5 V?
YES - Go to step 13.
NO - Go to step 12.
12. Measure voltage between PCM connector terminals C18 and C28.
Is there approx. 5 V?
YES - Repair open in the wire between the EGR valve and the PCM (C18).
NO - Substitute a known-good PCM and recheck. If the symptom/indication goes away, replace the original PCM.
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 more?
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 more?
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 PCM connector terminals C6 and C18.
Is there approx. 1.2 V?
YES - Go to step 20.
NO - Go to step 19.
19. Check for continuity between PCM connector terminal C6 and body ground.
Is there continuity?
YES - Repair short in the wire between the EGR valve and the PCM (C6).
NO - Repair open in the wire between the EGR valve and the PCM (C6).
20. Turn the ignition switch OFF.
21. Disconnect the EGR valve 6P connector.
22. Connect the battery positive terminal to EGR valve 6P connector terminal No.4.
23. Start the engine and let it idle, then connect the battery negative terminal to EGR valve 6P connector terminal No.6.
Does the engine stall or run rough?
YES - Go to step 24.
NO - Replace the EGR valve.
24. Turn the ignition switch OFF.
25. Disconnect PCM connector B (25P).
26. Check for continuity between PCM connector terminal B7 and the EGR valve 6P connector terminal No.4.
Is there continuity?
YES - Go to step 27.
NO - Repair open in the wire between the EGR valve and the PCM (B7).
27. Check for continuity between PCM connector terminal B7 and body ground.
Is there continuity?
YES - Repair short in the wire between the EGR valve and the PCM (B7).
NO - Go to step 28.
28. Check for continuity between EGR valve 6P connector terminal No.6 and body ground.
Is there continuity?
YES - Substitute a known-good PCM and recheck. If the symptom/indication goes away, replace the original PCM.
NO - Repair open in the wire between the EGR valve and G101.