CM850 Electronic Control System – FAULT CODE 691

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Overview

Turbocharger Compressor Inlet Air Temperature Sensor Circuit SMALL | MEDIUM | LARGE

Circuit Description

The turbocharger compressor inlet air temperature sensor is used by the ECM to monitor the temperature of the intake air temperature coming into the turbocharger. The ECM monitors the voltage on the signal pin and converts this to a temperature value. This temperature is one of many inputs used by the ECM to control engine operation and emissions.

Component Location

The turbocharger compressor inlet air temperature sensor is located in the compressor casing of the turbocharger.
Refer to Procedure 100-002 for a detailed component location view.

Shop Talk

The turbocharger inlet air temperature sensor shares return wires in the engine harness with other sensors. An open return can cause multiple fault codes to be active. Before troubleshooting Fault Code 691, check for multiple fault codes. An extension harness between the main engine harness and the turbocharger compressor inlet temperature sensor may be used depending on the turbocharger arrangement.

Possible causes of this fault code:

• Open return circuit in the harness, connectors, or sensor
• Open signal circuit or short circuit to a voltage source
• Failed sensor.

The resistance of the sensor varies with temperature. The sensor resistance should conform to the values in the table shown below.

Refer to Troubleshooting Fault Code t05-691