Coolant temperature sensor (T79), voltage low
Check the cable harness between the coolant temperature sensor and control unit pins 58 and 35. If no fault is found, contact an Allison dealer.
What you'll see
No driver-visible symptom recorded.
System reaction
The Allison fault code number is: P2184.The fault code is set when the control unit has registered a coolant temperature that exceeds a calibrated value for more than 10 seconds.The fault code can only be set if the following are fulfilled: The control unit has found a retarder, an analogue engine temperature sensor and a PWM source which requests retarder.The function 'Retarder reduction and retarder gear preselection based on engine coolant temperature' is activated in the calibration.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 read a coolant temperature above a calibrated value.
A possible cause of the fault code is a short circuit to ground on the electrical cable to pin 35 on the control unit.