Chart C8-1,TCC Check
NOTE:
The following step numbers refer to the numbers in the accompanying flow chart(s).
- Checks voltage from ignition switch through brake switch, 2nd gear apply switch (if equipped), and TCC switch. Light should have turned on by 35 MPH. Due to variations in specific TCC calibrations, it is possible to have a narrow margin between 3rd gear apply switch closing (if equipped) and ECM grounding of the TCC circuit from ECM terminal "P". Test light may turn on momentarily within this margin.
- Checks ECM ground for TCC solenoid. Light should go off.
- This increases throttle opening to increase MVS output. If MVS output is too low, clutch will not apply. On some applications, running free does not require enough throttle opening to allow the transmission to shift.
- Checks for low voltage at MVS input at ECM. At wide open throttle, voltage should be approximately 5 volts. Too low a MVS output should prevent TCC from applying.
- Checks for VSS signal at ECM. VSS signal is necessary to engage TCC.
- Checks for open in circuits to terminal "S". ECM supplies 12 volts to this terminal through a resistor. Normally both circuits should have low voltage readings since circuits are normally closed with vehicle stopped. An open circuit will read about 12 volts.
- Switch(es) open when transmission up shifts. Check that transmission circuit functions normally by voltage going high (near battery voltage) as switches open.