Engine speed sensor, signal interference
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: P0726.The fault code can only be set if the check is activated in calibration, the engine speed is higher than 600 rpm and the current gear is not neutral.The fault code is set if any of the following occur: Implausibly large changes in engine speed when the rotational speed is above 600 rpm for more than 0.15 seconds.Signal disruption from the sensor.The control unit sets the engine speed to the same as turbine rotational speed.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 a disturbance in the signal from the engine speed sensor which is located on the input shaft.
A possible cause of the fault may be damage to the cable harness or a defective engine speed sensor.