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P1899: P/N Switch Performance: Testing

  1. Turn the ignition on. With the DRBIII®, read the PNP switch input state. While moving the gear selector through all gear positions Park to 1st and back to Park, watch the DRBIII® display. Did the DRBIII® display P/N and D/R in the correct gear positions? If yes, refer to the INTERMITTENT CONDITION  under SELF-DIAGNOSTIC SYSTEM. If no, go to the next step.
  2. Turn the ignition off. Disconnect the PCM harness connectors. Disconnect the TRS P/N switch harness connector. Measure the resistance between ground and the TRS T41 (P/N Sense) circuit. Is the resistance below 100 ohms? If yes, repair the short to ground in the TRS T41 (P/N Sense) circuit. If no, go to the next step.
  3. Measure the resistance of the TRS T41 (P/N Sense) circuit between the PCM C1 harness connector and TRS harness connector. Is the resistance below 5.0 ohms? If yes, go to next step. If no, repair the TRS 41 (P/N Sense) circuit for an open.
  4. Turn the ignition off. Reconnect Transmission Range Sensor harness connector. Move the Gear selector through all gear positions, from Park to 1st and back. While moving the gear selector through each gear, measure the resistance between ground and the TRS T41 (P/N Sense) circuit in the PCM C1 harness connector. The circuit is grounded in Park and Neutral and open in the other positions. Did the resistance change from above 100.0 k/ohms (open) to below 10.0 ohms (grounded)? If yes, go to the next step. If no, replace the TRS Assembly (P/N Switch).
    5. NOTE: Before continuing, check the PCM harness connector terminals for corrosion, damage, or terminal push out. Repair as necessary.
  5. Using the wiring diagram as a guide, inspect the wire harness and connectors. Pay particular attention to all power and ground circuits. If the there are no possible causes remaining, replace the Powertrain Control Module. Program the new PCM. See PROGRAMMING .
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