200-4R TCC Apply on Top of 2nd Gear
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Lockup applies on top of the 1-2 shift. This can also cause engine RPMs to drop during coast down to a stop, almost resulting in engine stall. This may happen all the time, or only when hot.
How to Diagnose
- Once lockup is applied, touch the brake pedal to release the converter clutch. The brake switch cuts power to the TCC apply solenoid.
- If lockup remains on, suspect a restricted TCC apply solenoid.
- If lockup releases when pressing the brake pedal, suspect a short to ground in the wire that goes from the TCC apply solenoid to the PCM.
How it Works
The TCC apply solenoid has no oil to it in 1st or Reverse. 2nd gear oil is fed to the TCC apply solenoid through a small orifice. The solenoid needs to be able to exhaust this oil when it is not energized. When the PCM provides a ground for TCC solenoid, it closes and fluid pressure builds between the solenoid and the TCC apply valve in the pump, and strokes the valve. When the solenoid is restricted, 2nd gear oil pressure cannot exhaust, and the TCC apply valve strokes causing the converter clutch to apply.
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