Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Torque Converter Clutch (TCC) Circuit Check: Notes
The automatic transmission TCC eliminates power loss of torque converter stage when vehicle is in a cruise condition. This allows the convenience of an automatic transmission and fuel economy of a manual transmission.
Fused battery ignition is supplied to TCC solenoid, located inside valve body, to shift a spool valve in order to modulate pressure to TCC.
PCM/TCM engages TCC by grounding circuit No. 422 to energize solenoid.
TCC will engage under the following conditions.
- Vehicle speed is greater than 30 MPH.
- Engine at normal operating temperature greater than 149°F (65°C).
- Transmission at normal operating temperature of 195°F (91°C).
- Throttle position sensor output is not changing, indicating a steady road speed.
- Brake switch is closed.
- 4th gear is indicated.
- No codes are stored.NOTE: Test numbers refer to numbers on diagnostic chart.
- This step checks for a shorted internal transmission harness or TCC solenoid.
- This step verifies power supply to the TCC solenoid.
- This step checks circuit No. 422 for a short to ground.
- This step checks PCM/TCM's ability to control the TCC solenoid. If bidirectional scan tester is not available, TCC may be activated by grounding ALDL test terminal "B" with ignition on and engine off.
Use the Manual With the Right Hardware
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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.
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