Engine speed sensor, no signal
Check the cable harness. Try fitting a new sensor and check whether the fault disappears.Contact an Allison dealer.
What you'll see
No driver-visible symptom recorded.
System reaction
The Allison fault code number is: P0727.The fault code can only be set if the check is activated in calibration. For the low engine speed test, the turbine speed must be above 400 rpm and the voltage must be switched on.The fault code is set if any of the following occur: Implausibly large changes (minimum 1,040 rpm) in engine speed.Shaft rotational speed is less than 61 rpm for more than 4 seconds.The fault code is cleared automatically, when the vehicle has completed 40 start-up cycles without the fault being detected again.
Diagnostic depth
There is no signal from the engine speed sensor which is located on the output shaft.
A possible cause of the fault may be damage to the cable harness or a defective rotational speed sensor.