CM850 Electronic Control System – FAULT CODE 271 (ISB/QSB (Automotive and Industrial Application)

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


Overview

CODE REASON EFFECT
Fault Code: 271
PID: S126
SPN: 1347
FMI: 4
LAMP: Amber
SRT: 

High Fuel Pressure Solenoid Valve Circuit – Voltage Below Normal or Shorted to Low Source. Electronic fuel control actuator shorted low.

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

Electronic Fuel Control Actuator Circuit
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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 electronic fuel control actuator is located on the engine-mounted fuel pump housing. The engine wiring 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 (electronic fuel control actuator coil is shorted internally) in the circuit for the electronic fuel control actuator. When excessive current or a short circuit is detected, the ECM driver to the electronic 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 activated 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.

Refer to Troubleshooting Fault Code t05-271

Last Modified:  08-Jul-2010