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Home >> Acura >> 1999 >> 3.5RL >> Repair and Diagnosis >> Engine Performance >> Testing & Diagnosis >> Engine Controls - Self-Diagnostics >> Diagnostic Tests >> DTC P1491: Insufficient EGR Valve Lift Detected

DTC P1491: Insufficient EGR Valve Lift Detected

  1. Perform PCM reset procedure. See PCM RESET PROCEDURE/CLEARING CODES  under SELF-DIAGNOSTIC SYSTEM. Start engine and run at 3000 RPM, with no load and transmission in Park or Neutral, until radiator fan comes on. Test drive vehicle for about 10 minutes. Keep engine speed at 1700-2500 RPM. If DTC P1491 resets, go to next step. If DTC 1491 does not reset, problem is intermittent. System is okay at this time. Check for poor connections or loose wires between EGR valve and PCM. Repair as necessary.
  2. Disconnect vacuum hose between EGR valve and EGR control solenoid valve from EGR valve. See VACUUM DIAGRAMS article. Connect vacuum gauge to hose. Start engine and allow to idle. If vacuum exists, go to next step. If vacuum does not exist, go to step  5 .
  3. Disconnect EGR control box 4-pin connector located at right rear of engine compartment. Recheck for vacuum at disconnected EGR vacuum hose. If vacuum does not exist, go to next step. If vacuum exists, inspect hose routing of entire EGR system. See VACUUM DIAGRAMS article. If all hoses are routed properly, replace EGR control solenoid valve.
  4. Turn ignition off. Disconnect PCM 26-pin connector. Check for continuity between ground and control box connector terminal No. 2 (Red wire). If continuity exists, repair short in Red wire between PCM 26-pin connector terminal No. 6 and EGR control solenoid valve. See WIRING DIAGRAMS article. If continuity does not exist, substitute a known-good PCM, then recheck. If symptom or indication goes away, replace original PCM.
  5. Connect vacuum pump to EGR valve. Start engine and allow to idle. Apply 8.0 in. Hg vacuum to EGR valve. If engine runs rough or stalls, and EGR valve holds vacuum, go to next step. If engine does not operate as specified, replace EGR valve.
  6. Turn ignition off. Disconnect EGR valve lift sensor 3-pin connector. Turn ignition on. Measure voltage between EGR valve lift sensor 3-pin connector terminals No. 1 (Green/Blue wire) and No. 3 (Yellow/Blue wire). If about 5 volts are present, go to next step. If about 5 volts are not present, go to step  8 .
  7. Measure voltage between 22-pin PCM connector terminals No. 21 (Yellow/Blue wire) and No. 22 (Green/Black wire). If about 5 volts are present, repair open circuit in wiring between EGR valve and PCM. If about 5 volts are not present, replace PCM.
  8. Turn ignition off. Measure resistance by backprobing between EGR valve lift sensor terminals No. 1 (Green/White) and No. 2 (White/Black wire). If continuity is present, replace EGR valve. If no continuity is present, go to next step.
  9. Measure resistance between EGR valve lift sensor 3-pin connector terminals No. 2 (White/Black wire) and No. 3 (Yellow/White wire). If 100 k/ohms or greater are present, go to next step. If less than 100 k/ohms are present, replace EGR valve.
  10. Reconnect EGR valve lit sensor 3-pin connector. Turn ignition on. Measure voltage between 22-pin PCM connector terminals No. 17 (Yellow/Blue wire) and No. 22 (Green/Black wire). If about 1.2 volts are present, go to next step. If about 1.2 volts are not present, measure continuity between ground and 22-pin PCM connector terminal No. 17. If continuity is present, repair short circuit in wiring between EGR valve and PCM. If continuity is not present, repair open circuit in wiring between EGR valve and PCM.
  11. Turn ignition off. Disconnect control box 4-pin connector. Turn ignition on. Measure voltage between ground and control box connector terminal No. 1 (Black/Yellow wire). If battery voltage is present, go to next step. If battery voltage is not present, repair open circuit in wiring between EGR control solenoid valve and 20-amp PCM fuse No. 20 in fuse/relay box located under instrument panel.
  12. Reconnect vacuum pump and gauge to vacuum hose as outlined in step  2 . Start and idle engine. At control box side, connect battery voltage to EGR control solenoid valve connector terminal No. 1 (Black/Yellow wire). Observe vacuum gauge and connect ground to EGR control solenoid valve connector terminal No. 2 (Red wire). If there is about 8.0 in. Hg vacuum within one second, go to next step. If there is not about 8.0 in. Hg vacuum within one second, turn ignition off. Check vacuum hoses for leaks, restrictions or misrouting. Repair as necessary. If hoses are okay, replace EGR control solenoid valve.
  13. Turn ignition off. Reconnect control box connector. Reconnect vacuum hose. Start and idle engine. Connect jumper wire between PCM 26-pin connector terminals No. 6 (Red wire) and No. 12 (Black wire). If engine stalls or runs rough, replace PCM. If engine does not stall or run rough, repair open circuit in wiring between PCM and EGR control solenoid valve.
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