Allison WTEC II Fault Code: 43 PID: SPN: 21 FMI: Low side driver, F solenoid circuit

Main code 43 indicates the ECU has detected an open solenoid low side driver (switch) or a low side (ground) solenoid wire shorted-to-ground. An open or short prevents the ECU from turning off the F or K solenoid on the high (power) and the low (ground) sides as required (described in Code 42 XX). A Code 43 XX can trigger a Code 45 XX.

If solenoid resistance is about 1?2 Ohms, a short-to-ground code may not be set but could cause a burned-out solenoid driver in the ECU. Replace the solenoid when this occurs (see appropriate transmission Service Manual for replacement procedure). If the solenoid driver is burned out, 69 XX codes will be set. See the troubleshooting procedure for 69 XX codes.