Circuit DescriptionThe water-in-fuel sensor is attached to the fuel filter. The engine control module (ECM) provides a 5 volt reference signal to the water-in-fuel sensor. When the water collected in the fuel filter covers the sensor probes, the water-in-fuel sensor pulls the 5-VDC reference voltage to ground, indicating high water accumulation in the fuel filter. Component LocationThe water-in-fuel sensor is integrated into the bottom of the OEM supplied suction fuel filter. Conditions for Running the DiagnosticsThis diagnostic runs continuously when the keyswitch is in the ON position or when the engine is running. Conditions for Setting the Fault CodesThe Engine...

Circuit DescriptionThe engine oil temperature sensor is a variable resistor sensor and is used to measure the temperature of the engine oil in the oil rifle. The engine control module (ECM) supplies 5 volts to the engine oil temperature signal circuit. The ECM monitors the change in voltage caused by changes in the resistance of the sensor to determine the engine oil temperature. When the oil temperature is cold, the sensor or thermistor resistance is high. The ECM signal voltage only pulls down a small amount through the sensor to a ground. Therefore, the ECM senses a high signal voltage...

Circuit DescriptionThe OEM truck manufacturer can install a permit switch in the dash or send an inhibit message via the J1939 data link to the engine ECM. The function of the inhibit message is to prevent the aftertreatment system from performing mobile regenerations. Component LocationThe aftertreatment regeneration permit switch can be an actual switch in the vehicle dash or it can be a J1939 message sent via the J1939 data link. Refer to the OEM service manual. Conditions for Running the DiagnosticsThis diagnostic runs continuously when the engine is running. Conditions for Setting the Fault CodesThe Engine Control Module (ECM)...

Circuit DescriptionCertain anti-lock braking (ABS) controllers communicate with the engine control module (ECM) through the SAE J1939 data link. Under certain driving conditions, the anti-lock braking (ABS) controller can send a cruise control inhibit message to the ECM and cruise control will temporarily be disabled. Component LocationThe SAE J1939 data link wiring and the SAE J1939 devices vary by OEM options. Conditions for Running the DiagnosticsThis diagnostic runs continuously when the engine is running. Conditions for Setting the Fault CodesThe Engine Control Module (ECM) disabled cruise control due to an anti-wheel slip message from the anti-lock braking (ABS) controller. Action...

Circuit DescriptionThe aftertreatment diesel exhaust fluid (DEF) sensor is a smart device that communicates to the ECM via the J1939 datalink. The aftertreatment DEF sensor performs its own internal diagnostics and reports malfunctions back to the primary engine control module via the J1939 datalink. The aftertreatment DEF sensor monitors the tank level, temperature and quality of the DEF fluid. Component LocationThe aftertreatment diesel exhaust fluid (DEF) sensor is located in the aftertreatment DEF tank. Location of the tank and sensor is OEM dependent. Refer to the OEM service manual. Conditions for Running the DiagnosticsThis diagnostic runs continuously when the keyswitch...