Main code 64 indicates the ECU has detected a voltage signal from the retarder request modulation sensor (consisting of a module and a retarder control device) in either the high or low error zone. These codes can be caused by faulty wiring, faulty connections to the resistance module or retarder control device, a faulty resistance module, a faulty retarder control device, or a faulty ECU. Power wire 133 and ground wire 135 for the retarder modulation request sensor share a common power and ground with the TPS and OLS devices. A short-to-ground on the common power wire causes a ?sensor failed low? code for the other devices (Codes 21 12, and 14 12).
Allison WTEC II Fault Code: 64 PID: SPN: 12 FMI: Retarder modulation request sensor, failed low
Allison WTEC II Fault Code: 63 PID: SPN: 41 FMI: Pump/pack and a neutral general purpose input
Allison WTEC II Fault Code: 63 PID: SPN: 40 FMI: Service brake status input failed on
Allison WTEC II Fault Code: 63 PID: SPN: 26 FMI: Kickdown input failed on
Allison WTEC II Fault Code: 63 PID: SPN: 00 FMI: Input function fault
Allison WTEC II Fault Code: 62 PID: SPN: 23 FMI: Retarder oil temperature sensor, failed high
