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DTC P0579: Speed Control Switch #1 Performance: Testing

  1. Ignition on, engine not running. With the DRBIII® scan tool, monitor each switch junction for the speed control switches. Press and release each speed control button, (Resume/Accel - Cancel - Decel (Coast) - On/Off - Set). Does each switch function change status when pressing and then depressing each switch? If yes, see INTERMITTENT CONDITION  under SELF-DIAGNOSTIC SYSTEM. If no, go to next step.
  2. Turn the ignition off. Remove the speed control switches from the steering wheel. Measure the resistance across each switch control switch. Monitor the ohmmeter while pressing each function button on each switch. Resume/Accel (15,400 ohms), Cancel (900-918 ohms), Decel (Coast) (2910-2970 ohms), On/Off (0 ohm), Set (6584-6716 ohms). Does the function on the speed control switches have the correct ohm value? If yes, go to next step. If no, replace the speed control switch that had the incorrect resistance value.
  3. Turn the ignition off. Disconnect the speed control On/Off Switch harness connector. Disconnect the speed control Resume/Accel switch harness connector. Disconnect the PCM harness connectors. Measure the resistance between the (V37) S/C switch signal circuit and the (K4) sensor ground circuit in the speed control harness connector. Is the resistance below 5.0 ohms? If yes, repair the (V37) S/C switch signal circuit shorted to the (K4) sensor ground circuit. If no, go to next step.
  4. Turn the ignition off. Disconnect the speed control On/Off switch harness connector. Disconnect the speed control Resume/Accel switch harness connector. Disconnect the PCM harness connectors. Measure the voltage of the (V37) speed control switch signal circuit at the speed control harness connector. Is the is the voltage above 5.0 volts? If yes, repair the (V37) S/C switch signal circuit shorted to the battery voltage. If no, go to next step.
  5. Turn the ignition off. Disconnect the speed control On/Off switch harness connector. Disconnect the speed control Resume/Accel switch harness connector. Disconnect the PCM harness connectors. Measure the resistance between ground and the (V37) SIC switch signal circuit at the speed control harness connector. Is the resistance below 100 ohms? If yes, repair the (V37) speed control switch signal circuit shorted to the ground. If no, go to next step.
    6. 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.
  6. The measurement must be taken from both speed control switch harness connectors. Turn the ignition off. Disconnect the speed control On/Off switch harness connector. Disconnect the speed control Resume/Accel switch harness connector. Disconnect the PCM harness connectors. Measure the resistance of the (V37) S/C switch signal circuit from the speed control harness connector to the appropriate terminal of Miller Special Tool (8815). Is the resistance below 5.0 ohms for both measurements? If yes, go to next step. If no, repair the (V37) speed control switch signal circuit for an open.
    7. 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.
  7. The measurement must be taken from both speed control switch harness connector. Turn the ignition off. Disconnect the speed control On/Off switch harness connector. Disconnect the speed control Resume/Accel switch harness connector. Disconnect the PCM harness connectors. Measure the resistance of the (K4) sensor ground circuit from the speed control harness connector to the appropriate terminal of Miller Special Tool (8815). Is the resistance below 5.0 ohms for both measurements? If yes, go to next step. If no, repair the (K4) sensor ground circuit for an open.
  8. Before continuing disconnect the PCM harness connector and check the related wiring terminals for corrosion, damage or terminal push out. Repair as necessary. Pay particular attention to all power and ground circuits. If there are no possible causes remaining, replace and program the PCM. See PROGRAMMING .
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