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Home >> Acura >> 2003 >> 3.2CL Base >> Repair and Diagnosis >> Engine Performance >> System >> Engine Performance System Self-Diagnostics >> Diagnostic Tests >> DTC P1491: Exhaust Gas RECIRCULATION Valve Insufficient Lift Detected
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DTC P1491: Exhaust Gas RECIRCULATION Valve Insufficient Lift Detected

  1. Perform PCM reset procedure. See PCM RESET PROCEDURE/CLEARING DIAGNOSTIC TROUBLE CODES  under SELF-DIAGNOSTIC SYSTEM. Start engine and run at 3000 RPM, with no load (in park or neutral) until radiator fan comes on. Test drive vehicle for about 10 minutes. Keep engine speed at 1700-2500 RPM. Check temporary DTC with scan tool. If temporary DTC P1491 is set, go to next step. If temporary DTC 1491 did not set, problem is intermittent. System is okay at this time. Check for poor connection(s) or loose wire(s) between PCM and EGR valve. Repair as necessary.
  2. Turn ignition switch off. Disconnect EGR valve 6-pin harness connector. Start and idle engine. Measure voltage between EGR valve 6-pin harness connector terminals No. 4 (Blue/Red wire) and 6 (Black wire). See appropriate wiring diagram under ENGINE PERFORMANCE in WIRING DIAGRAMS. If battery voltage is not present, go to next step. If battery voltage is present, substitute known-good PCM, then recheck. If symptom or indication goes away, replace original PCM.
  3. Turn ignition switch off. Turn ignition switch back on. Measure voltage between EGR valve 6-pin harness connector terminals No. 2 (Green/Yellow wire) and 3 (Yellow/Blue wire). If about 5 volts are not present, go to next step. If about 5 volts are present, go to step  5 .
  4. Measure voltage between PCM 31-pin "C" harness connector terminals No. 18 (Green/Yellow wire) and 28 (Yellow/Blue wire - A/T) or PCM 31-pin "A" harness connector terminals No. 28 (Green/Yellow wire) and 30 (Yellow/Blue wire - M/T). If about 5 volts are present, repair open in Green/Yellow wire between PCM 31-pin "C" harness connector terminal No. 18 (A/T) or PCM 31-pin "A" harness connector terminal No. 28 (M/T) and EGR valve 6-pin harness connector terminal No. 2. If about 5 volts are not present, substitute known-good PCM, then recheck. If symptom or indication goes away, replace original PCM.
  5. Turn ignition switch off. Measure resistance between EGR valve 6-pin connector terminals No. 1 and 2. See appropriate wiring diagram under ENGINE PERFORMANCE in WIRING DIAGRAMS. If less than 100 k/ohms are present, go to next step. If 100 k/ohms or more are present, replace EGR valve.
  6. Measure resistance between EGR valve 6-pin connector terminals No. 1 and 3. If less than 100 k/ohms are present, go to next step. If 100 k/ohms or more are present, replace EGR valve.
  7. Reconnect EGR valve 6-pin harness connector. Turn ignition switch on. Measure voltage between PCM 31-pin "C" harness connector terminals No. 6 (White/Black wire) and 18 (Green/Yellow wire - A/T) or PCM 31-pin "A" harness connector terminals No. 16 (White/Black wire) and 28 (Green/Yellow wire - M/T). If about 1.2 volts are not present, go to next step. If about 1.2 volts are present, go to step  9 .
  8. Check for continuity between ground and PCM 31-pin harness connector terminal No. 6 (White/Black wire - A/T) or PCM 31-pin "A" harness connector terminals No. 16 (White/Black wire - M/T). If continuity is present, repair short in White/Black wire between PCM 31-pin harness connector terminal No. 6 (White/Black wire - A/T) or PCM 31-pin "A" harness connector terminals No. 16 (White/Black wire - M/T) and EGR valve 6-pin harness connector terminal No. 1. If continuity is not present, repair open in White/Black wire between PCM 31-pin harness connector terminal No. 6 (White/Black wire - A/T) or PCM 31-pin "A" harness connector terminals No. 16 (White/Black wire - M/T) and EGR valve 6-pin harness connector terminal No. 1.
  9. Turn ignition switch off. Disconnect EGR valve 6-pin harness connector. Connect fused jumper wire between positive battery terminal and EGR valve 6-pin connector terminal No. 4. Start and idle engine. Using second fused jumper wire, connect ground to EGR valve 6-pin connector terminal No. 6. If engine stalls or runs rough, go to next step. If engine does not stall or run rough, replace EGR valve.
  10. Turn ignition switch off. Disconnect PCM 25-pin "B" harness connector (A/T) or PCM 24-pin "B" harness connector (M/T). Check for continuity between ground and PCM 25-pin harness connector terminal No. 7 (Blue/Red wire - A/T) or PCM 24-pin "B" harness connector terminal No. 3 (Blue/Red wire - M/T). If continuity is not present, go to next step. If continuity is present, repair short in Blue/Red wire between PCM 25-pin harness connector terminal No. 7 (Blue/Red wire - A/T) or PCM 24-pin "B" harness connector terminal No. 3 (Blue/Red wire - M/T) and EGR valve 6-pin harness connector terminal No. 4.
  11. Connect fused jumper wire between ground and EGR valve 6-pin harness connector terminal No. 4. Check for continuity between ground and PCM 25-pin harness connector terminal No. 7 (Blue/Red wire - A/T) or PCM 24-pin "B" harness connector terminal No. 3 (Blue/Red wire - M/T). If continuity is present, go to next step. If continuity is not present, repair open in Blue/Red wire between EGR valve 6-pin harness connector terminal No. 4 and PCM 25-pin harness connector terminal No. 7 (Blue/Red wire - A/T) or PCM 24-pin "B" harness connector terminal No. 3 (Blue/Red wire - M/T).
  12. Disconnect jumper wire from EGR 6-pin harness connector. Check continuity between ground and EGR valve 6-pin harness connector terminal No. 6 (Black wire). If continuity is present, substitute known-good PCM, then recheck. If symptom or indication goes away, replace original PCM. If continuity is not present, repair open in Black wire between ground terminal G101 and EGR valve 6-pin harness connector terminal No. 6.
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