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DTC P0551: Power Steering Switch Performance: Testing

  1. Ignition on, engine not running. With the DRBIII® scan tool, read DTCs and record the related freeze frame data. Is the Good Trip Counter displayed and equal to zero? If yes, go to next step. If no, see INTERMITTENT CONDITION  under SELF-DIAGNOSTIC SYSTEM.
  2. Turn the ignition off. Disconnect the power steering pressure switch harness connector. Measure the resistance between ground and the PSP switch (Z1) ground circuit at the power steering pressure switch connector. Is the resistance below 5.0 ohms? If yes, go to next step. If no, repair the open in the PSP switch (Z1) ground circuit.
  3. Turn the ignition off. Disconnect the power steering pressure switch harness connector. Disconnect the PCM harness connectors. Measure the resistance between ground and the (K10) PSP switch signal circuit at the switch connector. Is the resistance below 100 ohms? If yes, repair the short to ground in the (K10) PSP switch signal circuit. If no, go to next step.
    4. CAUTION: Do not probe the PCM harness connectors. Probing the PCM harness connectors will damage the PCM terminals resulting in poor terminal to pin connection. Install Miller Special Tool (8815) to perform diagnosis.
  4. Turn the ignition off. Disconnect the power steering pressure switch harness connector. Disconnect the PCM harness connectors. Measure resistance of power steering (K10) PSP switch signal circuit from the power steering pressure switch harness connector to the appropriate terminal of Miller Special Tool (8815). Is the resistance below 5.0 ohms? If yes, go to next step. If no, repair the open in the (K10) PSP switch signal circuit.
  5. Turn the ignition off. Disconnect the power steering pressure switch harness connector. Ignition on, engine not running. Connect a jumper wire to the (K10) PSP switch signal circuit at harness connector. Using the DRBIII® scan tool, while monitoring the power steering pressure switch. Touch the jumper wire to the ground circuit at the power steering pressure switch harness connector several times. Did the power steering pressure switch status change from HI to LOW? If yes, replace the power steering pressure switch. If no, go to next step.
  6. Before continuing, check the PCM harness connector terminals for corrosion, damage, or terminal push out. Repair as necessary. If there are no possible causes remaining, replace and program the PCM. See PROGRAMMING .
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