Pinpoint Test C: The Transmission Control Switch (TCS) Is Inoperative

C1 CHECK THE VOLTAGE TO THE TRANSMISSION CONTROL SWITCH
- Key in OFF position.
- Disconnect: Transmission Control Switch C279.
- Key in ON position.
- Measure the voltage between TCS C279-3, Circuit 911 (WH/LG), harness side and ground.
  
  Fig 1: Disconnect Transmission Control Switch C279
  Courtesy of FORD MOTOR CO.
- Is the voltage greater than 10 volts?
1. Yes: GO to C2.
2. No: REPAIR the circuit. TEST the system for normal operation.
C2 CHECK THE TCS
- Measure the resistance between TCS Pin 3 (component side), and TCS Pin 4 (component side), while depressing and releasing the TCS.
  
  Fig 2: Measuring Resistance Between TCS Pin 3 (Component Side) And TCS Pin 4 (Component Side)
  Courtesy of FORD MOTOR CO.
- Is the resistance less than 5 ohms with the TCS depressed and greater than 10,000 ohms with the TCS released?
1. Yes: GO to C3.
2. No: INSTALL a new TCS. Test the system for normal operation.
C3 CHECK CIRCUIT 224 (TN/WH) FOR AN OPEN
- Key in OFF position.
- Disconnect: PCM C175.
- Measure the resistance between TCS C279-4, Circuit 224 (TN/WH), harness side and PCM C175-29, Circuit 224 (TN/WH), harness side.
  
  Fig 3: Measuring Resistance Between TCS C279-4 & PCM C175-29
  Courtesy of FORD MOTOR CO.
- Is the resistance less than 5 ohms?
1. Yes: REFER to INTRODUCTION - CNG, FLEX-FUEL & GASOLINE .
2. No: REPAIR the circuit. TEST the system for normal operation.