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DTC P0551: Power Steering Switch Failure: Testing

  1. Turn ignition on, engine not running. With the DRBIII®, read DTCs. Is the 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 Power Steering Pressure Switch harness connector. Power Steering Pressure Switch is located in high pressure power steering hose, underneath Power Steering Pump. With the ignition on and the engine not running, connect a jumper wire to the (K10) Power Steering Pressure Switch Signal circuit at harness connector. Using the DRBIII®, while monitoring the Power Steering Pressure Switch. Touch the jumper wire to the (Z1) 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 the next step.
    NOTE: Remove the jumper wire before continuing.
  3. Turn the ignition off. Disconnect the PCM harness connectors. Measure the resistance of (K10) Power Steering Pressure Switch Signal circuit from the PCM harness connector to the Power Steering Pressure Switch harness connector. Is the resistance below 5.0 ohms? If yes, go to next step. If no, repair the open in the (K10) Power Steering Pressure Switch Signal circuit.
  4. Measure resistance between ground and the (K10) Power Steering Pressure Switch Signal circuit at the Power Steering Pressure Switch harness connector. Is the resistance below 100 ohms? If yes, repair the short to ground in the (K10) Power Steering Pressure Switch Signal circuit. If no, go to the next step.
  5. With a 12-volt test light connected to 12-volts, probe the (Z1) Power Steering Pressure Switch ground circuit at the Switch harness connector. Does the test light illuminate brightly? If yes, go to the next step. If no, repair the open in the (Z1) Power Steering Pressure Switch ground circuit.
    6. NOTE: Before continuing, check the PCM harness connectors 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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