Cummins ISB CM850 (2003-06) Fault Code: 187 (Auto) PID: SID 232 SPN: 1080 FMI: 4 Sensor Supply Voltage Number 2 Circuit – Voltage Below Normal or Shorted to Low Source. Low voltage detected at the sensor supply number 2 circuit.

Posted by PerDiezel Solutions on January 18, 2026

Low voltage on the +5-VDC SUPPLY line can be caused by a short circuit to ground in a SUPPLY line, a short circuit between a SUPPLY line or a RETURN line, a malfunctioning sensor, or a malfunctioning ECM power supply.

On-Board Diagnostics (OBD) Information (Euro 4 Certified Engines):

1)The ECM illuminates the malfunction indicator lamp (MIL) when the diagnostic runs and fails.
2)The ECM turns OFF the MIL after 3 consecutive ignition cycles that the diagnostic runs and does not fail. The MIL lamp and fault code can also be cleared using INSITE? electronic service tool.
3)The fault code will be cleared from memory after 40 consecutive drive cycles where the diagnostic runs and passes.

OBD Information (Euro 4 Stage 1+ Certified Engines):

1)The ECM illuminates the MIL when the diagnostic runs and fails.
2)An engine torque derate will be activated after 50 hours of engine operation with the fault code active.
3)The ECM turns OFF the MIL after one ignition cycle that the diagnostic runs and passes. The MIL lamp cannot be cleared using INSITE? electronic service tool.
4)The fault code will be cleared from memory after 400 days or 9600 hours of engine operation.

OBD Information (Euro 4 Stage 1 + Certified Engines):

1)The ECM illuminates the MIL when the diagnostic runs and fails.
2)An engine torque derate will be activated after 50 hours of engine operation with the fault code active.
3)The ECM turns OFF the MIL after one ignition cycle that the diagnostic runs and passes. The MIL lamp can not be cleared using INSITE? electronic service tool.
4)The fault code will be cleared from memory after 400 days or 9600 hours of engine operation.

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 be identified using the method below:

1)Disconnect the ECM connector
2)Disconnect the camshaft position sensor
3)Disconnect the intake manifold pressure/temperature sensor
4)Check for continuity between the intake manifold pressure/temperature sensor RETURN pin and the camshaft position sensor RETURN pin
5)Check for continuity between ECM pin 47 and the camshaft position sensor RETURN pin
6)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.

Possible repairs:

1)Replace the harness.
2)Replace the camshaft engine position sensor.
3)Replace the intake manifold pressure sensor.
4)Replace the ECM.
5)Replace the engine harness.

Cummins ISB CM850 (2003-06) Fault Code: 155 (Marine) PID: 105 SPN: 105 FMI: 0 Intake Manifold 1 Temperature – Data Valid but Above Normal Operational Range – Most Severe Level. Intake manifold air temperature signal indicates intake manifold air temperature above engine protection critical limit.

Cummins ISB CM850 (2003-06) Fault Code: 155 (Auto) PID: 105 SPN: 105 FMI: 0 Intake Manifold 1 Temperature – Data Valid But Above Normal Operating Range – Most Severe Level. Intake manifold air temperature signal indicates intake manifold air temperature above engine protection critical limit.

Cummins ISB CM850 (2003-06) Fault Code: 154 PID: 105 SPN: 105 FMI: 4 Intake Manifold Air Temperature Sensor Circuit – Voltage Below Normal or Shorted to Low Source. Low signal voltage detected at intake manifold air temperature circuit.

Cummins ISB CM850 (2003-06) Fault Code: 153 PID: 105 SPN: 105 FMI: 3 Intake Manifold Air Temperature Sensor Circuit – Voltage Above Normal or Shorted to High Source. High signal voltage detected at intake manifold air temperature circuit.

Cummins ISB CM850 (2003-06) Fault Code: 151 (Marine) PID: 110 SPN: 110 FMI: 0 Engine Coolant Temperature – Data Valid but Above Normal Operational Range – Most Severe Level. Engine coolant temperature signal indicates engine coolant temperature above engine protection critical limit.

Cummins ISB CM850 (2003-06) Fault Code: 151 (Auto) PID: 110 SPN: 110 FMI: 0 Engine Coolant Temperature – Data Valid but Above Normal Operational Range – Most Severe Level. Engine coolant temperature signal indicates engine coolant temperature above engine protection critical limit.

WARNING!