Control unit supply voltage (U30) too high
â–¶ How to fix
Check the battery, associated cable harness and the vehicle's alternator. Ensure that the cable harness between gearbox and control unit is not damaged. If no fault is found, contact an Allison dealer.
What you'll see
No driver-visible symptom recorded.
System reaction
No system-reaction text recorded.
Diagnostic depth
Detection
The control unit supply voltage has exceeded a specified value.
Possible cause
Cause of this fault code can be: Fault on the vehicle's charging system.Loose connection or damaged cable harness.A 12 V control unit has been installed in a 24 V electrical system.