CM871 and CM876 Electronic Control Systems, ISX and ISM Engines – FAULT CODE 234

Engine Crankshaft Speed/Position – Data Valid but Above Normal Operational Range – Most Severe Level


Fault Code: 234
PID: P190
SPN: 190
FMI: 0/0

Engine Crankshaft Speed/Position – Data Valid but Above Normal Operational Range – Most Severe Level. Engine speed signal indicates engine speed above engine protection limit.

Fuel injection disabled until engine speed falls below the overspeed limit.

Camshaft Position Sensor and Engine Speed Sensor Circuit

Circuit Description

The crankshaft position and camshaft position sensors are hall effect type sensors. The electronic control module (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 to determine the position of the engine by the ECM.

Component Location

The crankshaft speed sensor is located on the intake side of the engine near the number 6 cylinder at the crankshaft centerline. The camshaft speed sensor is located below the fuel pump in the back of the gear housing. Refer to Procedure 100-002 (Engine Diagrams) in Section E for a detailed component location view.

Conditions for Running the Diagnostics

This diagnostic runs when the engine is running.

Conditions for Setting the Fault Codes

The ECM detects that the engine speed has exceeded the calibration limit for excessive engine speed.

Action Taken When the Fault Code is Active

  • Fueling to the engine is stopped until the engine speed drops to normal operating speeds.

Conditions for Clearing the Fault Code

The ECM will turn off the red STOP ENGINE light immediately after the engine speed drops to normal operating speeds.

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, recalibrate the ECM. Refer to Procedure 019-032 (ECM Calibration Code) in Section 19 in the corresponding Troubleshooting and Repair Manual for the engine being serviced.

Possible causes of this fault code include:

  • External fuel sources drawn into the intake air passage.
  • Reverse powering (motoring) of the engine.
  • Tampering of the engine speed/position sensors.

Inspect the intake manifold for sources of flammable vapors. Check the turbocharger seals to verify that there are no oil leaks. Inspect the engine speed/position sensors for damage or tampering.

Refer to Troubleshooting Fault Code t05-234

Last Modified:  09-Jul-2010