Allison 3000 & 4000 Gen 4 Fault Code: P0752 Shift Solenoid 1 (SS1) Valve Performance Stuck On (C1 Latch Valve Stuck)

DIAGNOSTIC RESPONSE:
DNS

CIRCUIT DESCRIPTION:
The Transmission Control Module (TCM) uses data received from the engine speed sensor and the turbine speed sensor to calculate torque converter slip value. The TCM then compares this calculated slip value to a preset value in the TCM calibration.

CONDITIONS FOR RUNNING THE DTC:
1. Hydraulic system is pressurized.
2. Hydraulic default condition not present.
3. Number of drive cycles more than 10 since last test.
4. Neutral or Neutral Very Low (NVL) attained.
5. C5 clutch pressure command not changing.
6. Output speed less than 50 rpm when throttle position is less than 15%.
7. Engine speed less than 450 rpm when torque converter slip is less than 125 rpm.
8. Previous drive cycle turbine speed is less than 200 rpm in range.

CONDITIONS FOR SETTING THE DTC:
If conditions are met for running the DTC, this test commands the Pressure Control Solenoid 1 (PCS 1) to pressurize while the vehicle is stopped in Neutral Very Low (NVL) in order to determine if C1 latch valve is stuck in a stroked position. If C1 latch is stuck stroked, C1 clutch will pressurize causing the turbine shaft to lock with the output shaft in NVL and the DTC becomes active.

ACTION TAKEN WHEN THE DTC SETS:
1. DTC is stored in TCM history.
2. The CHECK TRANS light illuminates.
3. Range limited to Neutral (N), Reverse (R), and 2nd through 4th range.

CONDITIONS FOR CLEARING
Use the diagnostic tool to clear the DTC from the TCM history. The TCM automatically clears the DTC from the TCM history if the vehicle completes 40 warm-up cycles without the DTC recurring.

DIAGNOSTIC AIDS:
NOTE: C1 latch valve does not have a solenoid located in the valve bore. C2 latch valve has Shift Solenoid 1 (SS1) located in the valve bore. This test determines if C1 latch valve is stuck.

DTC P0752 may be caused by:
1. Stuck C1 latch valve.
2. Issue with SS1.
3. Issue with TCM.