CM870 and ISX Engines – FAULT CODE 123

Intake Manifold Pressure Sensor Circuit

Overview

CODE	REASON	EFFECT
Fault Code: 123 PID: P102 SPN: 102 FMI: 4/4 LAMP: Amber SRT:	Intake Manifold Pressure Sensor Circuit – shorted low. Low signal voltage detected at intake manifold pressure circuit.	Derate in power output of the engine.

Intake Manifold Pressure Sensor Circuit SMALL | MEDIUM | LARGE

Circuit Description

The intake manifold pressure sensor monitors intake manifold pressure and passes information to the electronic control module (ECM) through the engine harness. If intake manifold pressure becomes too low, it will cause a derate condition.

Component Location

The intake manifold pressure sensor is located in the air intake horn. Refer to Procedure 100-002 for a detailed component location view.

Shop Talk

The intake manifold pressure sensor shares supply and return wires in the engine harness with other sensors. Opens and Shorts in the engine harness can cause multiple fault codes to be active. Before troubleshooting Fault Code 123 check for multiple faults.

Possible causes of this fault code include:

• Signal circuit open or shorted to ground, in the engine harness or sensor.
• Supply line open or shorted to ground.

Refer to Troubleshooting Fault Code t05-123