Circuit DescriptionThe ECM contains the calibration-specific parameter to control the engine’s performance and diagnostics. The fuel pump has its own calibration to interpret the ECM message and controlthe pump. If the fueling calibration in the ECM is altered or tampered with, this fault will belogged. Component LocationThe logic for the fault code is contained in the ECM circuitry. Shop TalkThis fault code is meant to detect out-of-range values and protect the fuel pump fromexcessive duty cycles from illegal calibration tampering. If this code is active or has high inactive counts, the fuel pump control module has detected an out of...

Circuit DescriptionThe ECM contains the calibration-specific parameter to control the engine’s performance and diagnostics. The fuel pump has its own calibration to interpret the ECM message and controlthe pump. If the fueling calibration in the ECM is altered or tampered with, this fault will belogged. Component LocationThe logic for the fault code is contained in the ECM circuitry. Shop TalkThis fault code is meant to detect out-of-range values and protect the fuel pump fromexcessive duty cycles from illegal calibration tampering. If this code is active or has high inactive counts, the fuel pump control module has detected an out of...

Circuit DescriptionThis diagnostic is meant to act as a speed and fueling rationality check between the enginecontrol module (ECM) and the fuel pump control module. Component LocationThe logic for this fault code is contained in the ECM and the fuel pump control module. Shop TalkFalse alarms caused by speed transitions, such as sudden accelerations or engine stallchecks, can trigger this fault code. Cummins ISB CM550 (1990-94) Fault Code: 375 PID: SID 254 SPN: FMI: 2 Engine Control Module (ECM) Fuel Calibration Corrupted Cummins ISB CM550 (1990-94) Fault Code: 375 PID: 602 SPN: FMI: 2 Engine Control Module (ECM) Fuel Calibration...

Circuit DescriptionThis circuit is internal to the ECM. If the keyswitch is turned off and the ECM still detectsmessages being sent from the fuel pump, the ECM will log this fault. Component LocationThis circuit logic is internal to the ECM. Shop Talk1) Some older ISB engines use a different original equipment manufacturer (OEM) interfaceconnector than illustrated.2) Fault Code 377 can be caused by a stuck fuel pump relay. If voltage is detected at pin 7of the fuel pump connector, with the keyswitch in the OFF position, check for a faulty fuelpump relay. Cummins ISB CM550 (1990-94) Fault Code: 376 PID:...

Circuit DescriptionThe intake air heater improves starting and white smoke control in cold ambient conditions.The ECM controls relays that switch power to the air heater. There are two heating coils in the heater that are individually controlled by the ECM. Component LocationThe intake air heater is located at the air inlet connection into the intake manifold. The location of the heater relays will vary with the OEM. Shop Talk1) These faults could also indicate the intake air heater circuits are shorted to battery (+).This would command the grids to be on full time. This will drain the batteries, burn outgrids,...