Allison WTEC II Fault Code: 42 PID: SPN: 25 FMI: Short-to-battery, K solenoid circuit

Main code 42 indicates the ECU has detected a short-to-battery condition in a solenoid wiring circuit. Solenoid K have a second driver on the low (ground) side which can turn off the solenoid. Even though the driver can be turned off, a stuck solenoid is shorted-to-battery which means it is continuously powered at an unregulated 12V or 24V instead of a regulated (pulse width modulated) voltage. A power-side driven solenoid stuck closed will not allow current regulation and the same code will occur. Eventually, the solenoid coil will burn up and become open. If the vehicle is turned off and restarted, a Code 41 XX occurs in early units and a Code 45 XX in later units.

Subcode will not trigger the DO NOT SHIFT light.