Cummins ISB CM850 (2003-06) Fault Code: 271 (ISC – Auto) PID: SID 126 SPN: 1347 FMI: 4 High Fuel Pressure Solenoid Valve Circuit – Voltage Below Normal or Shorted to Low Source. Low signal voltage detected at the fuel pump actuator circuit.

Cummins ISB CM850 (2003-06) Fault Code: 271 (ISC – Auto) PID: SID 126 SPN: 1347 FMI: 4 High Fuel Pressure Solenoid Valve Circuit – Voltage Below Normal or Shorted to Low Source. Low signal voltage detected at the fuel pump actuator circuit.

This fault becomes active when the ECM detects a short circuit in the electronic fuel control actuator circuit. Causes for this fault code are short circuit to ground or low resistance (fuel control actuator coil is shorted internally) in the circuit for the fuel pump actuator. When excessive current or a short circuit is detected, the ECM driver to the fuel control actuator is turned off to protect the circuit. It is necessary to cycle the keyswitch off and then back on before the ECM will retest for the cause of the fault code. The ECM driver is reenabled at key-on; and if the cause is no longer present, the fault code will become inactive and can be cleared. If the fault code is intermittent, look for causes of an intermittent short to ground in the wiring harness or connectors. Since the ISC and ISL engines utilize a 2-stage fuel rail pressure relief valve, failures to the fuel pump actuator will result in operation with the fuel rail pressure relief valve open. Extended operation with the fuel rail pressure relief valve open can damage the pressure relief valve.

Fault Code 2311 may have high counts if the fault condition is or was intermittent.

Possible repairs:

1)Replace the fuel pump actuator.
2)Repair the damaged harness, connector, or pins if possible.
3)Repair or replace the engine harness.
4)Replace the ECM.