Part 2 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 - 2 Of 3):

Numbers below refer to circled numbers on diagnostic chart.
1. Some "SCAN" tools display the state of these switches in different ways. Be familiar with the tool being used. Since both switches should be in the closed state during this test, the "SCAN" tool should show the same indication either the 2nd, 3rd, or 4th gear switch.
2. Determines whether the swtich or signal circuit is open. The circuit can be checked for an open by measuring the voltage at the TCC connector with a voltmeter. Should be about 12 volts.
3. Because the switches should be grounded in this step. Disconnecting the TCC connector should cause the "SCAN" to show a change in switch logic state.