Cumminz

Circuit DescriptionFuel pump self-test is provided at power-up. In an ideal case, an active Fault Code 374indicates a fuel pump defect and can trigger the engine light/malfunction indicator light at key on. Component LocationThe fuel pump is located on the backside of the gear housing. Refer to Procedure 100-002 inSection E for detailed component location. Shop TalkIf Fault Code 374 becomes active while the engine is operating, it can possibly be due to apower glitch or to voltage spikes. Check the power supply circuit for loose or shorted wires and/or fuses. Inspect the power supply relay.

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.

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.