CM871 and CM876 Electronic Control Systems, ISX and ISM Engines – FAULT CODE 1926

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Overview

ISX – Aftertreatment 1 Fuel Pressure Sensor Circuit SMALL | MEDIUM | LARGE

ISM – Aftertreatment 1 Fuel Pressure Sensor Circuit SMALL | MEDIUM | LARGE

Circuit Description

The aftertreatment fuel pressure sensor is used to monitor the fuel pressure into the aftertreatment system. The electronic control module (ECM) supplies the aftertreatment fuel pressure sensor a 5 volt reference voltage. When the fuel pressure is low, the sensor signal voltage is low. When the fuel pressure is high, the sensor signal voltage is near the 5 volt reference voltage. The ECM monitors the aftertreatment fuel pressure signal circuit voltage to calculate the pressure of the fuel within the aftertreatment system.

Component Location

The aftertreatment fuel pressure sensor is located in the aftertreatment shutoff valve assembly. Use this procedure for a detailed component location view. Refer to Procedure 100-002 in Section E.

Conditions for Running the Diagnostics

This diagnostic runs within the first minute after the engine is started and prior to active regeneration of the aftertreatment particulate filter.

Conditions for Setting the Fault Codes

The ECM detects that the aftertreatment fuel pressure sensor is reading an erratic value, or the aftertreatment fuel pressure reading is not changing with the engine operating conditions.

Action Taken When the Fault Code is Active

• The ECM illuminates the amber CHECK ENGINE light immediately when the diagnostic runs and fails.
• A calculated value of aftertreatment fuel pressure is used for aftertreatment operation.

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, calibrate the ECM. Refer to Procedure 019-032 in Section 19.

Within the first minute after starting the engine, an aftertreatment pressure diagnostic cycles the aftertreatment fuel shutoff valve and aftertreatment fuel injector to check for leaks and proper operation. One of the initial checks opens the secondary aftertreatment fuel shutoff valve and opens the aftertreatment fuel injector. This relieves all of the pressure in the aftertreatment fuel line. At this check point, the aftertreatment fuel pressure sensor should read ambient air pressure. If the sensor reading does not read ambient pressure within the sensor tolerance, this fault code will be logged.

Possible causes of this fault code include:

• A malfunctioning in-range aftertreatment fuel pressure sensor
• A stuck closed secondary aftertreatment fuel shutoff valve
• A plugged aftertreatment fuel drain line
• A plugged aftertreatment fuel supply line
• A plugged fuel filter
• High fuel return restriction.

Refer to Troubleshooting Fault Code t05-1926