CM2150 Electronic Control System – FAULT CODE 1899

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Overview

ISB, ISC, and ISL – Differential Pressure Sensor SMALL | MEDIUM | LARGE

Circuit Description

The exhaust gas recirculation (EGR) differential pressure sensor has two ports that sense exhaust pressure. The sensor outputs a voltage which represents the pressure difference between the two ports. The electronic control module (ECM) uses this pressure to determine how much exhaust gas is flowing in the EGR connection tube to the intake manifold. This information is used to control the EGR valve for correct emission levels.

The ECM provides a 5 volt supply to the EGR differential pressure sensor on the sensor supply circuit. The ECM also provides a ground on the sensor return circuit. The EGR differential pressure sensor provides a signal to the ECM on the EGR differential pressure sensor signal circuit. This sensor signal voltage changes based on the differential pressure in the EGR crossover tube.

The EGR differential pressure sensor measures the exhaust gas pressure drop across the EGR differential pressure orifice. This pressure drop is used to calculate the amount of EGR flow into the intake manifold.

Component Location

The sensor is located near the air intake. Use the following procedure for a detailed component location view. Refer to Procedure 100-002 in Section E.

Conditions for Running the Diagnostics

This diagnostic runs continuously when the following conditions are met:

• EGR valve position is greater than 5 percent open
• Engine speed is greater than a calibratible value
• Engine torque output is greater than a calibratible value.

Conditions for Setting the Fault Codes

• EGR differential pressure is less than a calibratible value.

Action Taken When the Fault Code is Active

• The ECM illuminates the amber CHECK ENGINE light immediately when the diagnostic runs and fails.
• The EGR valve operation will be disabled.

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.

This diagnostic checks the EGR differential pressure sensor reading when the EGR valve is open. Since the EGR valve is open, the reading of the EGR differential pressure must be greater than zero. If the ECM detects a reading lower than expected with the EGR valve open, this fault code is logged.

Possible causes of this fault code include:

• A malfunctioning EGR differential pressure sensor
• A stuck closed EGR valve
• EGR differential pressure sensor flow port cross-drillings are plugged with soot
• A fouled EGR cooler.

Refer to Troubleshooting Fault Code 1899.