SPN 102 - FMI 4 (Fault Code 123)

SPN102 FMI4
Intake Manifold Pressure Sensor Circuit - Voltage Below Normal or Shorted to Low Source

Original Wiring Harness - Intake Manifold Pressure Sensor Circuit

CODES:
Fault Code: 123
PID(P), SID(S): P102
SPN: 102
FMI: 4/4
Lamp: Amber
SRT:

Revised Wiring Harness - Intake Manifold Pressure Sensor Circuit

REASON: Intake Manifold Pressure Sensor Circuit - Voltage Below Normal or Shorted to Low Source. Low signal voltage detected at the intake manifold pressure circuit.

EFFECT:
Automotive: Derate in power output of the engine.
Marine: None - No engine protection for circuit sensor failure.

Circuit Description:
The intake manifold pressure sensor monitors intake manifold pressure and passes information to the electronic control module (ECM) through the engine harness. On automotive applications, if the intake manifold pressure becomes too low, it will cause a derate condition.

For marine applications, no derate condition occurs. There is no engine protection for a circuit or sensor failure.

Component Location:
The intake manifold pressure sensor is located in the air intake horn.

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.

The sensor return configuration for Euro 4 ISB engines has been changed for automotive wiring harnesses manufactured from February 2012 onward. The new style wiring harnesses can be identified using the method below:
• Disconnect the ECM connector
• Disconnect the camshaft position sensor
• Disconnect the intake manifold pressure/temperature sensor
• Check for continuity between the intake manifold pressure/temperature sensor RETURN pin, and the camshaft position sensor RETURN pin.
• Check for continuity between ECM pin 47 and the camshaft position sensor RETURN pin
• Use the table below to determine which harness is fitted to the engine.

NOTE: QSB engines, all C series engines, and all L series engines are not affected by this change.


Read More:
SPN 102 - FMI 3 (Fault Code 122)
SPN 612 - FMI 2 (Fault Code 115)








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