CM871 and CM876 Electronic Control Systems, ISX and ISM Engines – FAULT CODE 115

Engine Magnetic Speed/Position Lost Both of Two Signals – Data Erratic, Intermittent, or Incorrect


Fault Code: 115
PID: P190
SPN: 612
FMI: 2/2

Engine Magnetic Speed/Position Lost Both of Two Signals – Data Erratic, Intermittent, or Incorrect. The electronic control module (ECM) has detected that the primary and backup speed sensor signals are connected backwards.

None on performance.

ISM – Engine Magnetic Speed/Position
ISX – Engine Magnetic Speed/Position

Circuit Description

The crankshaft position and camshaft position sensors are Hall effect type sensors. The ECM provides a 5 volt supply to the position sensor and a return circuit. As the teeth on the crankshaft speed ring or the dimples in the back of the camshaft gear move past the position sensor, a signal is generated on the position sensor signal circuit. The ECM interprets this signal and converts it to an engine speed. A missing tooth on the crankshaft gear is used by the ECM to determine the position of the engine.

Component Location

Both engine position sensors are located on the back side of the front gear housing above the fuel pump drive. Refer to Procedure 100-002 in Section E for a detailed component location view.

Conditions for Running the Diagnostics

This diagnostic runs continuously when the engine is running.

Conditions for Setting the Fault Codes

The ECM detects that the crankshaft position and camshaft position signal inputs to the ECM are reversed.

Action Taken When the Fault Code is Active

  • The ECM illuminates the red STOP ENGINE light immediately when the diagnostic runs and fails.
  • The ECM detects the reversed sensors and continues to operate.

Conditions for Clearing the Fault Code

The ECM will turn off the red STOP ENGINE light immediately after the diagnostic runs and passes.

Shop Talk

Verify the electronic control module (ECM) calibration is correct. Check the calibration revision history found on QuickServe™ Online for applicable fixes to the calibration stored in the ECM. If necessary, calibrate the ECM. Refer to Procedure 019-032 in Section 19 in the corresponding Troubleshooting and Repair Manual for the engine being serviced.

This fault code indicates that the camshaft position sensor and crankshaft position sensor wiring harness connectors are reversed. On the ISM engine, the two camshaft position sensor connectors are reversed.

Refer to Troubleshooting Fault Code t05-115

Last Modified:  09-Jul-2010