Circuit DescriptionThe electronic control module (ECM) provides a 5-VDC supply to the engine crankshaft speed/position sensor on the sensor supply circuit. The ECM also provides a ground on the sensor return circuit. The crankshaft speed/position sensor provides a signal to the ECM on the crankshaft speed/position sensor signal circuit. This sensor generates a signal to the ECM as the crankshaft speed indicator ring passes the sensor. The ECM interprets this signal into an engine speed reading and determines engine position.
Component LocationThe crankshaft position sensor location varies depending on the engine.
Conditions for Running the DiagnosticsThis diagnostic runs continuously when the engine is running.
Conditions for Setting the Fault CodesThe ECM detects a loss of the crankshaft speed/position sensor while the engine is running.
Action Taken When the Fault Code is ActiveThe ECM illuminates the amber CHECK ENGINE light and/or the Malfunction Indicator Lamp (MIL) immediately when the diagnostic runs and fails.The camshaft speed sensor is used to provide engine speed and position information to the ECM.Diesel exhaust fluid injection into the aftertreatment system is disabled.Active and stationary regeneration of the diesel particulate filter will be disabled.The EGR valve will be closed.Engine torque will be reduced if the engine is operated for an extended period of time with this fault active.Conditions for Clearing the Fault CodeTo validate the repair, start the engine and let it idle for 1 minute.The fault code status displayed by the INSITE? electronic service tool will change to INACTIVE immediately after the diagnostic runs and passes.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 the INSITE? electronic service tool can be used to clear active and inactive faults, as well as extinguish the MIL for OBD applications.
Shop TalkCauses of this fault include:
Open or short circuit of the +5-VDC supply, signal, or return wire in the engine harnessDamaged or malfunctioning engine speed sensorDamaged tone wheelSensor air gap that is too small or too large.
Possible Cause:1) Engine Wiring Harness2) Sensor failure3) ECM calibration