Solenoid PCS3 jammed in disengaged position
Contact an Allison dealer.
What you'll see
No driver-visible symptom recorded.
System reaction
The Allison fault code number is: P0796.The fault code is set when the control unit detects a predefined number of times that next gear ratios are incorrect.For the fault code to be set, the following conditions must be met: The hydraulic system is pressurised.Output shaft speed is higher than 125 rpm.Turbine rotational speed is higher than 60 rpm.Cold mode is not activated.The lock-up cannot be locked. The control unit shuts off gear changing adaptation. The control unit attempts to engage the previous gear.While the fault code is active, the control unit ignores all information from the drive mode selector. The fault code is cleared automatically, when the vehicle has completed 40 start-up cycles without the fault being detected again.
Diagnostic depth
The control unit has detected slipping in a clutch (C3 or C5) which PCS3 supplies with hydraulic pressure.
The cause can be: Irregular sensor signal from turbine or output shaft speed.Leak or obstruction in a supply circuit for a specific clutch.Defective solenoid.A governor valve for PCS3 has jammed.A locking valve for C1 or C2 has jammed.