Pinpoint Test I: Flash Code 4-Vehicle Speed Sensor (VSS) Circuit Failure

I1 CHECK THE SPEEDOMETER OPERATION
- Check the speedometer for correct operation by driving the vehicle.
- Does the speedometer operate correctly?
- Yes : GO to I2.
- No : REFER to INSTRUMENT CLUSTER to continue diagnosis of the speedometer.
I2 CHECK THE VSS CIRCUIT FOR AN OPEN
- Key in OFF position.
- Disconnect: Speed Control Actuator C122.
- Disconnect: Powertrain Control Module (PCM) C175b.
- Measure the resistance between the speed control actuator C122 pin 3, circuit 8-PG18 (WH/BU), harness side and the PCM C175b pin 1, circuit 8-RE22 (WH/VT), harness side.
  
  Fig 1: Checking VSS Circuit For An Open
  Courtesy of FORD MOTOR CO.
- Is the resistance less than 5 ohms?
- Yes : GO to I3.
- No : REPAIR the circuit. TEST the system for normal operation.
I3 CHECK THE VSS CIRCUIT FOR A SHORT TO GROUND
- Measure the resistance between the speed control actuator C122 pin 3, circuit 8-PG18 (WH/BU), harness side and ground.
  
  Fig 2: Measuring Resistance Between Speed Control Actuator C122 Pin 3, Circuit 8-PG18 (WH/BU), Harness Side And Ground
  Courtesy of FORD MOTOR CO.
- Is the resistance greater than 10,000 ohms?
- Yes : INSTALL a new speed control actuator. REFER to SPEED CONTROL ACTUATOR . TEST the system for normal operation.
- No : REPAIR the circuit. TEST the system for normal operation.