Diagnostic Routine B

Diagnostic Routine B

Diagnostic Overview

TCS (Transmission Control Switch)

Refer to Wiring Diagram Set 29 for schematic and connector information Electrical Diagrams.

Normal Operation and Fault Conditions

The TCS (Transmission Control Switch) is a momentary contact switch located on the selector lever. Pressing the TCS (Transmission Control Switch) will engage or disengage the O/D (Overdrive) function of the transmission. When the O/D (Overdrive) is disengaged, the O/D (Overdrive) icon will illuminate OFF on the IPC (Instrument Panel Cluster). Each time the ignition switch is cycled, the transmission will automatically provide O/D (Overdrive) operation regardless of TCS (Transmission Control Switch) position the last time the engine was running.

DTC Fault Trigger Conditions






Pinpoint Test

NOTE: If the scan tool is unable to communicate with the PCM (Powertrain Control Module) or access the transmission PIDs (Parameter Identifications), REFER to Computers and Control Systems Information.

1. Read and record all DTCs (Diagnostic Trouble Codes)

1. Install the scan tool and record all DTCs (Diagnostic Trouble Codes).

Is DTC (Diagnostic Trouble Code) P1780 set?






2. Check the BCM (Body Control Module) fuse

1. Ignition OFF.

2. Remove the BCM (Body Control Module) fuse 41 (7.5A).

3. Check fuse 41 (7.5A).

Is the resistance less than 5 ohms?






3. Check the BCM (Body Control Module) for an internal short

1. Disconnect the BCM (Body Control Module) C2280B.

2. Inspect for damaged or pushed out terminals.

3. Install a new fuse.

Did the fuse fail?






4. Check the TCS (Transmission Control Switch) power circuit for a short to ground

1. Disconnect selector lever C2008.

2. Measure the resistance of circuit CBP41 (BU) from selector lever C2008-6 to ground.





Is the resistance greater than 10,000 ohms?






5. Check the TCS (Transmission Control Switch) signal input circuit for a short to ground

1. Disconnect the PCM (Powertrain Control Module) C175T.

2. Measure the resistance of circuit CET34 (BN/GN) between selector lever harness C2008-5 and ground.





Is the resistance greater than 10,000 ohms?






6. Check the TCS (Transmission Control Switch) power circuit for an open

1. Disconnect the selector lever C2008.

2. Disconnect the BCM (Body Control Module) C2280B.

3. Measure the resistance of circuit CBP41 (BU) from selector lever C2008-6 to the BCM (Body Control Module) C2280B-3.





Is the resistance less than 5 ohms?






7. Check the TCS (Transmission Control Switch) signal input circuit for an open

1. Disconnect the PCM (Powertrain Control Module) C175T.

2. Measure the resistance of circuit CET34 (BN/GN) between selector lever C2008-5 to the PCM (Powertrain Control Module) C175T-31.





Is the resistance less than 5 ohms?






8. Check the TCS (Transmission Control Switch)

1. Measure the resistance between selector lever C2008-5 and C2008-6 while cycling the TCS (Transmission Control Switch).





Is the resistance less than 5 ohms with the switch pressed and greater than 10,000 ohms when released?






9. Check the PCM (Powertrain Control Module)

1. Connect the BCM (Body Control Module) C2280B.

2. Connect the selector lever C2008.

3. Ignition ON.

4. Measure the voltage on circuit CET34 (BN/GN) at the PCM (Powertrain Control Module) C175T-31 to ground while cycling the TCS (Transmission Control Switch).





Is the voltage greater than 10 volts with the switch pressed, and less than 5 volts with the switch released?