CM850 Electronic Control System – FAULT CODE 271 (ISC/QSC/ISL/QSL Automotive, Industrial, and Marine Application)

High Fuel Pressure Solenoid Valve Circuit – Voltage Below Normal or Shorted to Low Source


Fault Code: 271
PID: S126
SPN: 1347
FMI: 4
LAMP: Amber

High Fuel Pressure Solenoid Valve Circuit – Voltage Below Normal or Shorted to Low Source. Low signal voltage detected at the fuel pump actuator circuit.

Engine will run poorly at idle. Engine will have low power. Fuel pressure will be higher than commanded.

Electronic Fuel Control Actuator Circuit

Circuit Description

The circuit is a pulse width modulated (PWM) driver in the Electronic Control Module (ECM) that controls the electronic fuel control actuator. The actuator is grounded in the ECM. The actuator is normally open. Pulse width modulation (PWM) duty cycle to the electronic fuel control actuator depends on the difference between desired rail pressure and sensed rail pressure.

Component Location

The fuel pump actuator is located on the engine-mounted fuel pump. The engine siring harness and the ECM are other components in the circuit that can cause this fault code Refer to Procedure 100-002 for a detailed component location view.

Shop Talk

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.

Refer to Troubleshooting Fault Code t05-271

Last Modified:  08-Jul-2010