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HOMESERVICE MANUALSGMC1984PICKUP K2500, 6.2 C, STANDARDREPAIR AND DIAGNOSIS (SINGLE PAGE)ENGINE PERFORMANCESYSTEMDIESEL CEC TESTINGTCC CHECK
1984 GMC Pickup K2500, 6.2 C, Standard

TCC Check

1984 GMC Pickup K2500, 6.2 C, StandardSECTION TCC Check

The torque converter clutch (TCC) is designed to eliminate power loss during cruise driving conditions. When the TCC is applied, the conventional fluid coupling between the engine and transmission is replaced by a straight-through mechanical coupling. The heart of the system is the TCC solenoid located inside the transmission which is controlled by the ECM. The ECM completes the ground to activate the TCC solenoid for clutch engagement.

The ECM completes the circuit whenever the TPS exceeds a calibrated value for throttle opening.

NOTE: The following step numbers refer to the numbers in the accompanying flow chart(s).
  1. This step checks for complete circuit from ignition through solenoid, up to test point. The test light should be on because the ECM has not completed the circuit yet.
  2. This step checks the ECM's ability to complete the circuit to ground to energize the TCC solenoid and engage the TCC. The test light should go out when the ECM completes the circuit.
  3. This checks the TPS signal. If signal to ECM is correct voltage, fault is in ECM connection or ECM. If TPS signal to ECM is not correct voltage, proper operation will not occur.
  4. This checks for ground in circuit to ECM terminal "A2". The light should be off.
  5. This checks for ignition voltage to terminal "A" of TCC connector. Light should be on.
  6. This checks for complete circuit from ignition to ground via TCC test terminal in ALDL connector. Light should go on if harness is good.
Fig 1: TCC Check
G9493
RENDER: 1.0x

NO RELATED

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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • • You smell fuel, burning insulation, or see smoke.
  • • Brakes feel soft, pull hard to one side, or make grinding noises.
  • • The engine overheats, stalls repeatedly, or misfires under load.
  • • You are missing required tools, torque specs, or safe lifting equipment.
  • • You are not confident in the next step or safety outcome.