DTC P1491: EGR Valve Lift Insufficient Detected
- Perform PCM reset procedure. See PCM RESET PROCEDURE/CLEARING CODES . Connect SCS Service Connector (07PAZ-0010100) to 2-pin service check connector, located under passenger side of instrument panel. See Figure. Start engine and hold at 3000 RPM with no loads and transmission in Park or Neutral, until cooling fan comes on. Test drive vehicle for approximately 10 minutes with engine speed at 1700-2500 RPM. If DTC P1491 resets, go to next step. If DTC P1491 does not reset, problem is intermittent, system is okay at this time. Check for poor connections or loose wires between EGR valve and PCM connectors.
- Connect vacuum pump/gauge to EGR vacuum hose. Start engine and allow to idle. If vacuum does not exist at EGR vacuum hose, go to step 4). If vacuum exists at EGR vacuum hose, disconnect EGR control solenoid valve connector. Recheck EGR vacuum hose vacuum. If vacuum does not exist, go to next step. If vacuum exists, check EGR system vacuum hose routing. If EGR system hoses are okay, replace EGR control solenoid valve.
- Turn ignition off. Disconnect PCM 32-pin connector. See Figure. Check for continuity between ground and EGR control solenoid valve 2-pin connector terminal No. 2 (Red wire). If continuity exists, repair short in Red wire between EGR control solenoid valve and PCM 32-pin connector terminal No. 7. If continuity does not exist, substitute a known-good PCM and recheck. If DTCs do not reset, replace original PCM.
- Connect vacuum pump/gauge to EGR valve vacuum port. With engine at idle, apply 8 in. Hg of vacuum. If EGR valve holds vacuum and engine stalls or runs rough, go to next step. If EGR valve does not hold vacuum and/or engine does not stall or run rough, replace EGR valve.
- Turn ignition off. Disconnect EGR control solenoid valve 2-pin connector. Turn ignition on. Measure voltage between ground and EGR control solenoid valve connector terminal No. 1 (Black/Yellow wire). If battery voltage is present, go to next step. If battery voltage is not present, repair open in Black/Yellow wire between EGR control solenoid valve and ECU, CRUISE CONTROL fuse No. 4 (7.5-amp) located in underdash fuse/relay box.
- Connect vacuum pump/gauge to EGR valve vacuum port. Start engine and allow to idle. Using a jumper wire, connect battery voltage to valve side of EGR control solenoid valve terminal No. 1 (Black/Yellow wire). While observing vacuum gauge, connect battery ground to EGR control solenoid valve terminal No. 2 (Red wire). If about 8 in. Hg of vacuum is present within one second, go to next step. If about 8 in. Hg of vacuum is not present within one second, go to step 8).
- Turn ignition off. Reconnect EGR control solenoid valve 2-pin connector. Reconnect EGR valve vacuum hose. Start engine and allow to idle. Using a jumper wire, connect PCM connector terminals No. 7 (Red wire) and No. 10 (Black wire). If engine does not stall or run rough, repair open in Red wire between EGR control solenoid valve and PCM. If engine stalls or runs rough, substitute a known-good PCM and recheck. If DTCs do not reset, replace original PCM.
- Turn ignition off. Check for leaks, restrictions or misrouted vacuum hoses between EGR valve and intake manifold, and between EGR vacuum control valve and intake manifold. If vacuum hoses are okay, go to next step. If vacuum hoses are not okay, repair as necessary.
- Connect vacuum gauge to EGR control solenoid valve lower hose. Start engine and allow to idle. If about 6-8 in. Hg of vacuum is present, replace EGR control solenoid valve. If about 6-8 in. Hg vacuum is not present, repair or replace vacuum hose between EGR vacuum control valve and intake manifold. If vacuum hose is okay, replace EGR vacuum control valve.