Main code 23 indicates a fault with a shift selector or the wiring between a shift selector and the ECU.
Allison WTEC II Fault Code: 23 PID: SPN: 12 FMI: Primary Shift Selector or RSI Link Fault
Allison WTEC II Fault Code: 22 PID: SPN: 16 FMI: Output speed sensor reasonableness test
Allison WTEC II Fault Code: 22 PID: SPN: 15 FMI: Turbine speed sensor reasonableness test
Allison WTEC II Fault Code: 22 PID: SPN: 14 FMI: Engine speed sensor reasonableness test
Allison WTEC II Fault Code: 21 PID: SPN: 23 FMI: Throttle position sensor, failed high
Allison WTEC II Fault Code : 21 PID: SPN: 12 FMI: Throttle position sensor, failed low
