Allison 3000 & 4000 Gen 4 Fault Code: P2761 TCC PCS Control Circuit Open

DIAGNOSTIC RESPONSE:
Inhibit TCC operation

CIRCUIT DESCRIPTION:
The Torque Converter Clutch (TCC) Pressure Control Solenoid (PCS) is a normally closed solenoid used to apply the lockup clutch when specific engine and turbine speed conditions are met. The Transmission Control Module (TCM) commands the solenoid ON to produce hydraulic pressure in the lockup clutch apply circuit. When the TCC solenoid is commanded OFF, lockup clutch pressure is exhausted. The TCM sends control current to the TCC solenoid from High Driver 3 (HSD3) via wire 131. HSD3 is continuously ON unless the TCM detects a fault condition The TCM regulates the amount of current to the TCC solenoid by switching the TCC solenoid low side driver ON and OFF. Wire 137 completes the circuit between the TCC solenoid and its low side driver. DTC P2761 indicates that the DTC has detected a high resistance or an open condition in the low side of the TCC solenoid electrical circuit.

CONDITIONS FOR RUNNING THE DTC:
TCM initialized normally and engine speed above 200 rpm.

CONDITIONS FOR SETTING THE DTC:
This DTC sets when the TCM detects the TCC solenoid low side driver in a failed open state.

ACTION TAKEN WHEN THE DTC SETS:
When DTC P2761 is active:
1. The TCM inhibits TCC engagement.
2. DTC is store in the TCM history.
3. The CHECK TRANS light illuminates.
4. The TCM freezes shift adapts (DNA).

CONDITIONS FOR CLEARING THE DTC:
Use diagnostic tool to clear the DTC from the TCM history. The TCM automatically clears the DTC from the TCM history if the vehicle completes 4 warm-up cycles without failure.

DIAGNOSTIC AIDS:
DTC P2761 can be caused by:
1. TCC solenoid issues such as W137 high resistance or open circuit in the chassis harness.
2. W137 (terminal 12 of 20-way) high resistance or open circuit in the chassis harness.
3. Defective TCC solenoid.
4. Unlocked connectors, expanded terminals, poor pin crimps or unlocked pins causing high resistance or open circuit.
5. Defective TCM.

Review applicable information in Control System and Transmission Specifications to find additional circuit specifications, system and connector diagrams, and troubleshooting tips.