LEMON Manuals: Even more car manuals for everyone: 1960-2025
Home >> GMC >> 1985 >> Forward Control 7.4 W, Standard >> Repair and Diagnosis >> Engine Performance >> System >> Diesel CEC Tests W/Codes >> TCC Check
April 5, 2026: LEMON Manuals is launched! Read the announcement.

TCC Check

The Torque Converter Clutch (TCC) eliminates power loss during highway cruise conditions. An ECM controlled solenoid in the transmission activates the TCC.

Ignition power is supplied to the solenoid through a brake switch which opens when the brake is applied. The ECM completes the ground to activate the TCC solenoid for clutch engagement.

NOTE: The following step numbers refer to the numbers in the accompanying flow chart(s).
  1. Checks for complete circuit from ignition through solenoid to the test point.
  2. Checks that the ECM is completing the circuit to ground to engage the TCC.
  3. Checks for TPS signal to ECM.
  4. Checks ground circuit to ECM terminal "A2".
  5. Checks for ignition voltage to terminal "A" of the TCC harness connector.
  6. Checks for complete circuit from ignition to ground via TCC test terminal in ALCL.
Fig 1: Flow Chart, TCC Check
G10285
Fig 2: Flow Chart, TCC Check
GB0046427