Part 3 of 3, Gear Switch Diagnosis

Trans Gear Switch And Torque Converter Clutch Solenoid Circuit Diagram:

CIRCUIT DESCRIPTION
The second gear switch is open in third and fourth gear. The PCM uses this signal to disengage the TCC when going into a downshift. The fourth gear switch is open in fourth gear.

TEST DESCRIPTION

Chart C-8B, Torque Converter Clutch (TCC) Electrical Diagnosis (4T60 Trans - 3 Of 3):

Numbers below refer to circled numbers on diagnostic chart.
4. the switch state should change when the vehicle shifts into 2nd gear.

DIAGNOSTIC AIDS
If the vehicle is road tested to diagnose a TCC related problem, be sure the gear switch states do not change during testing. If the PCM detects a change in logic state of the gear switches, the TCC solenoid will be turned "OFF", disengaging the TCC.