CM871 and CM876 Electronic Control Systems, ISX and ISM Engines – FAULT CODE 3385

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Overview

ISX – Intake Manifold 1 Temperature Sensor Circuit SMALL | MEDIUM | LARGE

ISM – Intake Manifold 1 Temperature Sensor Circuit SMALL | MEDIUM | LARGE

Circuit Description

The intake manifold 1 temperature sensor is a variable resistor sensor and is used to measure the temperature of the air entering the intake manifold of the engine. The engine intake manifold temperature value is used by the electronic control module (ECM) for the engine protection system and engine emissions control.

The ECM supplies 5 volts to the intake manifold temperature signal circuit, and monitors the change in voltage caused by changes in the resistance of the sensor to determine the intake manifold temperature. When the intake air is cold, the sensor (or thermistor) resistance is high. The ECM signal voltage only pulls down a small amount through the sensor to a ground. Therefore, the ECM senses a high signal voltage or a low temperature. When the intake air is warm, the sensor resistance is low. The signal voltage pulls down a large amount. Therefore, the ECM senses a low signal voltage, or a high temperature.

Component Location

 The engine intake manifold temperature sensor is located in the air intake manifold.

Conditions for Running the Diagnostics

This diagnostic runs continuously when the engine is operating at idle.

Conditions for Setting the Fault Codes

The intake manifold temperature is less than 20°C [68°F] while the engine is operating at idle for an extended period of time.

Action Taken When the Fault Code is Active

• The ECM illuminates the amber CHECK ENGINE light immediately when the diagnostic runs and fails.

Conditions for Clearing the Fault Code

• To validate the repair, start the engine and let it idle for 1 minute.
• The fault code status displayed by INSITE™ electronic service tool will change to INACTIVE immediately after the diagnostic runs and passes.
• The ECM will turn off the amber CHECK ENGINE lamp after the diagnostic runs and passes.
• The “Reset All Faults” command in INSITE™ electronic service tool can be used to clear active and inactive faults.

Shop Talk

The EGR valve was closed because the engine was operating with cold intake manifold temperatures for an extended period of time. No repair is necessary.

Refer to Troubleshooting Fault Code t05-3385.