The TCC fault valve in GM 8L45 and 8L90 transmissions allows the regulated fluid to pass through and onto the release side of the TCC control valve. When signal pressure is applied to the TCC fault valve, this circuit is cut off and the pressure is removed from the release side of the TCC control valve.

Excessive wear in the TCC fault valve bore allows pressure loss and/or malfunctioning valve cycles that causes drivability concerns. If the regulated pressure is allowed to leak around the TCC fault valve, the pressure flowing through may cause malfunctions in the operations of the TCC control valve. Ultimately this could cause the torque converter to lock-up causing harsh shifts, burnt clutches and even damaging the converter. If the signal pressure is allowed to leak around the TCC fault valve, the circuit could potentially remain open and apply unwanted pressure to the release side of the TCC control valve. This could prevent the torque converter lock-up causing soft slide shifts or even no shift.

Reconditioning the bore and installing Sonnax oversized TCC fault valve 154740-41 corrects circuit pressures and restores proper valve functions.

• Hardcoat anodized aluminum valve combats premature wear
• Oversized valve maintains OE functions and pressures using OE Spring