Pinpoint Test C: The Transmission Control (TC) Switch Is Not Operating Correctly

WARNING: This page is about a different car, the 2007 Ford Ranger. However, it is still accessible from the selected car via links, so may be relevant.

C1 CHECK THE VOLTAGE TO THE TRANSMISSION CONTROL (TC) SWITCH
- Key in OFF position.
- Disconnect: Transmission Control (TC) Switch C279
- Key in ON position.
- Measure the voltage on circuit CBP20E (YE/VT) at the TC switch C279-1 and ground.
  
  Fig 1: Measuring Voltage On Circuit CBP20E (YE/VT) At TC Switch C279-1 & Ground
  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 TC SWITCH
- Measure the resistance between the TC switch C279-1 and the TC switch C279-2, component side, while depressing and releasing the TC switch.
  
  Fig 2: Measuring Resistance Between TC Switch C279-1 & TC Switch C279-2
  Courtesy of FORD MOTOR CO.
- Is the resistance less than 5 ohms with the TC switch depressed and greater than 10,000 ohms with the TC switch released?
1. YES : Go to C3.
2. NO : INSTALL a new TC switch. Test the system for normal operation.
C3 CHECK CIRCUIT CET34A (BN/GN) FOR AN OPEN
- Key in OFF position.
- Disconnect: Powertrain Control Module (PCM) Transmission Connector
- Measure the resistance of circuit CET34A (BN/GN) between the TC switch C279-2, and the PCM C175B-29.
  
  Fig 3: Measuring Resistance Of Circuit CET34A (BN/GN) Between TC Switch C279-2 & PCM C175B-29
  Courtesy of FORD MOTOR CO.
- Is the resistance less than 5 ohms?
1. YES : REFER to INTRODUCTION - GASOLINE ENGINES article.
2. NO : REPAIR the circuit. TEST the system for normal operation.