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DTC P1494: Leak Detection Pump SW Or Mechanical Fault: Testing

  1. Turn ignition on, engine not running. With the DRBIII®, read DTCs. Is the DTC Good Trip counter displayed and equal to zero? If yes, go to next step. If no, go to INTERMITTENT CONDITION  under SELF-DIAGNOSTIC SYSTEM.
  2. Turn the ignition off. Disconnect the vacuum supply hose at the Leak Detection Pump. Connect a vacuum gauge to the disconnected vacuum supply hose at the Leak Detection Pump. Start the engine and read the vacuum gauge. Does the vacuum gauge read at least 13 in. Hg? If yes, go to next step. If no, repair leak or obstruction in vacuum hose as necessary.
  3. Turn the ignition off. Reconnect vacuum supply hose at Leak Detection Pump. Disconnect Leak Detection Pump harness connector. Turn ignition on, engine not running. With the DRBIII® in Inputs/Outputs, read the Leak Detect Pump Sw state. While observing the Leak Detect Pump Sw state, connect a jumper wire between a good 12-Volt source (B+) and the LDP Switch Sense circuit. Did the Leak Detect Pump Sw state change when the jumper was connected? If yes, replace the Leak Detection Pump. If no, go to next step.
    NOTE: Remove the jumper wire before continuing.
  4. Turn the ignition off. Disconnect PCM harness connectors. Measure the resistance of the LDP Switch Sense Circuit from the PCM harness connector to LDP harness connector. Is the resistance below 5.0 ohms? If yes, go to next step. If no, repair the Leak Detection Pump Switch Sense Circuit for an open.
  5. Measure the resistance between ground and the LDP Switch Sense circuit at Leak Detection Pump harness connector. Is the resistance below 100 ohms? If yes, repair the LDP Switch Sense Circuit for a short to ground. If no, go to next step.
    6. NOTE: Before continuing, check the PCM harness connector terminals for corrosion, damage, or terminal push out. Repair as necessary.
  6. Using the wiring diagram as a guide, inspect the wire harness and connectors. Pay particular attention to all power and ground circuits. If there are no possible causes remaining, replace PCM. Program the new PCM. See PROGRAMMING .
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