Cummins ISB4.5 CM2150 Fault Code: 123 PID: 102 SPN: 102 FMI: 4 Intake Manifold 1 Pressure Sensor Circuit – Voltage Below Normal or Shorted to Low Source

Circuit Description
The engine control module (ECM) provides a 5 volt supply to the intake manifold pressure sensor on the sensor supply circuit. The ECM also provides a ground on the sensor return circuit. The intake manifold pressure sensor provides a signal to the ECM on the intake manifold pressure signal circuit. This sensor signal voltage changes based on the pressure in the intake manifold. The ECM will detect a low signal voltage at operating conditions such as during an idle or a deceleration. The ECM will detect a high signal voltage during high engine load operating conditons.

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

Conditions for Setting the Fault Codes
The ECM detects that the intake manifold pressure signal voltage is greater than a calibratible value for more than 1 second.

Action Taken When the Fault Code is Active
-The ECM illuminates the amber CHECK ENGINE light and/or the malfunction indicator lamp (MIL) immediately when the diagnostic runs and fails.
-A default value of the intake manifold pressure reading is used.
-The torque output of the engine will be reduced

Conditions for Clearing the Fault Code
-To validate the repair, start the engine and let it idle for 1 minute.

For engines equipped with selective catalytic reduction (SCR) aftertreatment:

-This fault code can not be cleared with INSITE™ electronic service tool.
-The ECM will turn off the amber CHECK ENGINE lamp and/or MIL immediately after the diagnostic runs and passes.
-Use INSITE™ electronic service tool to verify the fault code is inactive.
-The inactive fault code will be cleared from the memory after 9600 hours of engine operation without a reoccurrence.

For all other engines:

-The ECM will turn off the amber CHECK ENGINE lamp after the diagnostic runs and passes.
-For On-Board Diagnostic (OBD) engines, the ECM will turn off the MIL after 3 consecutive trips where the diagnostic runs and passes.
-The “Reset All Faults” command in INSITE™ electronic service tool can be used to clear active and inactive faults, as well as extinguish the MIL for OBD applications.

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 122, check for multiple faults.

Possible Causes
-Open return circuit in the engine harness, connectors, or sensor
-SIGNAL wire shorted to sensor supply or battery voltage.