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Home >> Dodge and Ram >> 2003 >> Durango Base, 5.9 Z, RWD >> Repair and Diagnosis >> External Pages >> Different car >> Section 15 (Engine Controls - Self Diagnostics - 4.7L) >> Diagnostic Tests >> DTC P0594: Speed Control Servo Power Circuit >> Testing

DTC P0594: Speed Control Servo Power Circuit: Testing

WARNING: This page is about a different car, the 2003 Dodge Dakota. However, it is still accessible from the selected car via links, so may be relevant.
  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 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 brake lamp switch harness connector. Using a 12-volt test light connected to ground, probe the (V32) S/C supply circuit in the switch harness connector while holding the cruise switch in the ON position. Does the test light illuminate brightly? If yes, go to next step. If no, go to step  7.
  3. Disconnect and remove the brake lamp switch. Measure the resistance across the (V32) S/C supply circuit terminal and the (V30) S/C brake switch output circuit terminal at the brake lamp switch. Push the plunger of the switch in and let it out. Does the resistance change from below 5.0 ohms to an open circuit? If yes, go to next step. If no, replace the brake lamp switch.
  4. Turn the ignition off. Connect the brake lamp switch harness connected and install the switch. Disconnect the speed control servo harness connector. Ignition on, engine not running. It is necessary to PRESS and HOLD the speed control switch in the ON position while checking for voltage. Using a 12-volt test light connected to ground, probe the (V30) S/C brake switch output circuit in the servo harness connector. Does the test light illuminate brightly? If yes, replace the S/C servo. If no, go to next step.
  5. Turn the ignition off. Disconnect the brake lamp switch harness connector. Measure the resistance of the (V30) S/C brake switch output circuit from the brake lamp switch harness connector to the S/C servo harness connector. Is the resistance below 5.0 ohms? If yes, repair the excessive resistance in the (V30) S/C brake switch output circuit. If no, go to next step.
  6. Measure the resistance between ground and the (V30) S/C brake switch output circuit at the speed control servo harness connector. Is the resistance below 100 ohms? If yes, repair the short to ground in the (V30) S/C brake switch output circuit. If no, go to next step.
    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. Turn the ignition off. Disconnect the PCM harness connectors. Measure the resistance of the (V32) S/C supply circuit from the brake lamp switch harness connector to the appropriate terminal of Miller Special Tool (8815). Is the resistance above 5.0 ohms? If yes, repair the open in the (V32) S/C supply circuit. If no, go to next step.
  8. Measure the resistance between ground and the (V32) S/C supply circuit in the brake switch harness connector. Is the resistance below 100 ohms? If yes, repair the short to ground in the (V32) S/C supply circuit. If no, go to next step.
    9. NOTE: Before continuing, disconnect the PCM harness connectors and check the related wiring terminals for corrosion, damage or terminal push out. Repair as necessary.
  9. Using the wiring diagram as a guide, inspect the wire harness and connectors. Visually inspect the related wire harness. Look for any chafed, pierced, pinched, or partially broken wires. Visually inspect both the component and the PCM connectors. 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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