Circuit DescriptionThe oil pressure sensor is used by the electronic control module (ECM) to monitor thelubricating oil pressure. The ECM monitors the voltage on the signal pin and converts this to apressure value. The oil pressure value is used by the ECM for the engine protection system. Component LocationThe oil pressure sensor is located on the engine block below the ECM. Shop TalkVerify, with the driver, the engine speed at which the fault occurs. If the engine is beingoperated at too low of a speed, the oil pressure can drop below the engine protection limits. Possible causes:1) Low oil level2)...

Circuit DescriptionThe oil pressure switch is used by the electronic control module (ECM) to detect the presenceof lubricating oil pressure. Component LocationThe oil pressure switch is located on the engine block below the ECM. Shop Talk1) Verify, with the driver, the engine speed at which the fault occurs. If the engine is beingoperated at too low of a speed, the oil pressure can drop below the engine protectionlimits.2) Connect a manual gauge to monitor actual oil pressure of the engine.3) Engines in the field can have had a jumper harness kit installed which connects the oilpressure switch to pin K...

Circuit DescriptionThe WIF sensor is attached to the fuel filter. The WIF sensor sends a signal to the electroniccontrol module (ECM) when a set volume of water has accumulated in the fuel filter. Component LocationThis fault code indicates that water has been detected in the water separation fuel filter. Drainthe water from the fuel filter. If this fault code is active and there is no water in the fuel filter, a malfunctioning Water-In-Fuelsensor is a likely cause. Reference the appropriate OEM wiring diagram when troubleshooting circuits that utilize wiringsupplied by the OEM. The WIF sensor is installed in the bottom...

Circuit DescriptionThe coolant level sensor monitors the coolant level within the coolant system and passesinformation to the engine control module (ECM) through the engine harness. This sensor isvery complex. Do not use a multimeter to check the coolant level sensor. If the radiator coolantlevel drops below a certain level, a progressive power derate with increasing time after alertwill occur. Component LocationThe coolant level sensor is located in the radiator top tank or surge tank. Shop TalkThis is an original equipment manufacturer (OEM)-supplied component and will vary in sensorlocation.1) If a shorting plug is used in the coolant level circuit, verify...

Circuit DescriptionThe WIF sensor is attached to the fuel filter. The WIF sensor sends a signal to the electroniccontrol module (ECM) when a set volume of water has accumulated in the fuel filter. The WIFcircuit contain two wires: A return ground (pin 20), and a signal wire (pin 40). Component LocationThe water-in-fuel sensor is installed in the fuel filter and is located on the side of the headapproximately midway on the engine. Cummins ISB CM550 (1990-94) Fault Code: 422 PID: 111 SPN: 111 FMI: 2 Colant Level Sensor Circuit Coolant Level Sensor Circuit Cummins ISB CM550 (1990-94) Fault Code: 418...