Pinpoint Test J: Flash Code 4 - Speed Signal Circuit Failure

WARNING: This page is about a different car, the 2004 Ford Ranger. However, it is still accessible from the selected car via links, so may be relevant.

J1 CHECK THE SPEEDOMETER OPERATION
- Check the speedometer for correct operation by driving the vehicle.
- Does the speedometer operate correctly?
1. Yes : GO to J2.
2. No : REFER to INSTRUMENT CLUSTER to continue diagnosis of the speedometer.
J2 CHECK CIRCUIT 679 (GY/BK) FOR AN OPEN
- Key in OFF position.
- Disconnect: Speed Control Actuator C122.
- Disconnect: PCM C175.
- Measure the resistance between the PCM C175 pin 68, circuit 679 (GY/BK), harness side and the speed control actuator C122 pin 3, circuit 679 (GY/BK), harness side.
  
  Fig 1: Checking Circuit 679 (GY/BK) For An Open
  Courtesy of FORD MOTOR CO.
- Is the resistance less than 5 ohms?
1. Yes : GO to J3.
2. No : REPAIR the circuit. TEST the system for normal operation.
J3 CHECK CIRCUIT 679 (GY/BK) FOR A SHORT TO GROUND
- Disconnect: SJB C2100a.
- Disconnect: Instrument Cluster C220b.
- Measure the resistance between the speed control actuator C122 pin 3, circuit 679 (GY/BK), harness side and ground.
  
  Fig 2: Checking Circuit 679 (GY/BK) For A Short To Ground
  Courtesy of FORD MOTOR CO.
- Is the resistance greater than 10,000 ohms?
1. Yes : INSTALL a new speed control actuator. REFER to SPEED CONTROL ACTUATOR . TEST the system for normal operation.
2. No : REPAIR the circuit. TEST the system for normal operation.