CM2150 Electronic Control System – FAULT CODE 271

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Overview

ISB, ISC and ISL with CM2150 – Fuel Pump Actuator Circuit SMALL | MEDIUM | LARGE

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. The 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 wiring harness and the ECM are other components in the circuit that can cause this fault code. Refer to Procedure 100-002 (Engine Diagrams) in Section F for a detailed component location view.

Conditions for Running the Diagnostics

This diagnostic runs continuously when the keyswitch is in the ON position.

Conditions for Setting the Fault Codes

The fuel pump actuator circuit PWM signal is not detected to be system voltage when the PWM signal is turned on.

Action Taken When the Fault Code is Active

• The ECM illuminates the amber CHECK ENGINE light immediately when the diagnostic runs and fails.
• Fuel rail pressure will be higher than the commanded rail pressure.

Conditions for Clearing the Fault Code

The ECM will turn off the amber CHECK ENGINE light immediately after the diagnostic runs and passes.

Shop Talk

Verify the electronic control module (ECM) calibration is correct. Check the calibration revision history found on QuickServe® Online for applicable fixes to the calibration stored in the ECM. If necessary, recalibrate the ECM. Refer to Procedure 019-032 (ECM Calibration Code) in Section 19 in the corresponding Troubleshooting and Repair Manual for the engine being serviced.

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 test again for the cause of the fault code. The ECM driver is enabled at key-on; 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.

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

Refer to Troubleshooting Fault Code t05-271