FixVault
Home › Acura › 1995 › 2.5TL › Repair and Diagnosis › Engine Performance › System › Engine Controls - Tests W/Codes › Trouble Codes › Code P1491 - Insufficient EGR Valve Lift

Code P1491 - Insufficient EGR Valve Lift

  1. Connect and operate scan tester, following manufacturer's instructions. Clear codes. Operate engine at 3000 RPM until radiator fan come son. Drive vehicle, keeping engine speed at 1700-2500 RPM. Retrieve codes. If Code P1491 appears, go to next step. If Code 1459 does not appear, problem is intermittent. Inspect for poor connections or loose wires associated with EGR valve and ECM, then repair as necessary.
  2. Disconnect No. 1 hose from EGR valve. Connect vacuum pump/gauge to hose. Start and idle engine. If vacuum exists, go to next step. If vacuum does not exist, go to step 5).
  3. Unplug 2-pin control box connector. Recheck for vacuum at No. 1 vacuum hose. If vacuum does not exist, go to next step. If vacuum exists, inspect hose routing of entire EGR system. If all hoses are routed properly, replace EGR control solenoid valve.
  4. Turn ignition off. Unplug 26-pin connector from ECM. Test for continuity between Red wire at control box harness connector and ground. If continuity does not exist, temporarily substitute known good ECM, then retest system. If continuity exists, repair shorted Red wire between ECM terminal No. A6 and EGR control solenoid valve.
  5. Move vacuum pump/gauge to EGR valve. Idle engine. Apply 7.87 in. Hg vacuum to EGR valve. If engine starts to run roughly or stall, and EGR valve holds vacuum, go to next step. If engine does not start to run roughly or stall, or EGR valve does not hold vacuum, replace EGR valve.
  6. Turn ignition off. Unplug 2-pin control box connector. Turn ignition on. Measure voltage at Black/Yellow wire at harness connector. If battery voltage exists, go to next step. If battery voltage does not exist, repair open Black/Yellow wire between EGR control solenoid valve and fuse panel.
  7. Reconnect vacuum pump/gauge to No. 1 hose. Start and idle engine. Connect battery voltage to control box terminal No. 1 (Black/Yellow wire on mating harness connector). While observing vacuum gauge, connect remaining control box connector terminal (Red wire on mating harness connector) to ground. If gauge indicates approximately 8 in. Hg within one second, go to next step. If gauge does not indicate approximately 8 in. Hg within one second, go to step 9).
  8. Turn ignition off. Reconnect wiring to control box. Reconnect No. 1 hose to EGR valve. Start and idle engine. Connect jumper wire between 26-pin ECM connector terminals A6 (Red wire) and A12 (Black wire). If engine stalls or runs roughly, temporarily substitute known good ECM, then retest system. If engine does not stall or run roughly, repair open Red wire between ECM and EGR control solenoid valve.
  9. Turn ignition off. Inspect EGR hoses for routing, restrictions, or leaks. If hoses are okay, go to next step. Repair or replace hoses as necessary.
  10. Disconnect lower hose from EGR control solenoid valve. Connect vacuum gauge to hose. Start and idle engine, If approximately 8 in. Hg vacuum exists, replace EGR control solenoid valve. If approximately 8 in. Hg vacuum does not exist, inspect No. 2 hose between EGR vacuum control valve and intake manifold. If hose is okay, replace EGR vacuum control valve.
About FixVault