PACCAR PX-9 CM2350 (2013-17) Fault Code:2557 PID:SID 57 SPN:697 FMI:3 Auxiliary PWM Driver 1 Circuit – Voltage Above Normal or Shorted to High Source

Reason:
Auxiliary PWM Driver 1 Circuit – Voltage Above Normal or Shorted to High Source. High signal voltage detected at the pulse width modulation (PWM) auxiliary circuit.

Effect:
Possible reduced engine performance.

Circuit Description:
The transmission shift modulator uses this signal from the electronic control module (ECM) to determine when to shift the transmission. The return circuit is dependent on original equipment manufacturer (OEM) wiring. It may be wired back to the ECM on some vehicles or wired to chassis or block ground on others. Consult the OEM wiring diagram for return circuit details.

Component Location:
Refer to the OEM wiring diagram for the location of the transmission shift modulator.

Conditions for Running the Diagnostics:
This diagnostic runs continuously when the engine is running.

Conditions for Setting the Fault Codes:
The Engine Control Module (ECM) detected high signal voltage at the analog torque circuit.

Action Taken When the Fault Code is Active:
The ECM illuminates the amber CHECK ENGINE lamp immediately when the diagnostic runs and fails.

Conditions for Clearing the Fault Code:
1) To validate the repair, start the engine and let it idle for 1 minute.
2) The fault code status displayed by INSITE™ electronic service tool will change to INACTIVE immediately after the diagnostic runs and passes.
3) The ECM will turn off the amber CHECK ENGINE lamp immediately after the diagnostic runs and passes.
4) The Reset All Faults command in INSITE™ electronic service tool can be used to clear active and inactive faults.

Shop Talk:
N/A

Possible Causes:
1) Malfunctioning transmission shift modulator
2) Open circuit in the output device driver return line
3) Pin-to-pin short in the output device driver line