Circuit DescriptionThis circuit is used for limp home acceleration if communication between the engine controlmodule (ECM) and fuel pump is lost. The circuit allows for a two-stage acceleration wherethere are only two engine speeds available throughout the full range of accelerator travel. Component LocationThis circuit is internal to the fuel pump control module and the engine ECM. Cummins ISB CM550 (1990-94) Fault Code: 369 PID: 1690 SPN: 1078 FMI: 2 Fuel Pump To Engine Synchronization Pulse Not Recognized Cummins ISB CM550 (1990-94) Fault Code: 368 PID: SID 254 SPN: 1078 FMI: 8 Fuel Pump Can Not Reach Commanded Timing Cummins...

Circuit DescriptionThis circuit is used for limp home acceleration if communication between the engine controlmodule (ECM) and fuel pump is lost. The circuit allows for a two-stage acceleration wherethere are only two engine speeds available throughout the full range of accelerator travel. Component LocationThis circuit is internal to the fuel pump control module and the engine ECM. Cummins ISB CM550 (1990-94) Fault Code: 372 PID: 1283 SPN: 1077 FMI: 11 Idle Select High/Low Cummins ISB CM550 (1990-94) Fault Code: 369 PID: 1690 SPN: 1078 FMI: 2 Fuel Pump To Engine Synchronization Pulse Not Recognized Cummins ISB CM550 (1990-94) Fault Code:...

Circuit DescriptionThis circuit provides a secondary fuel shutoff signal from the engine control module (ECM) to the fuel pump. Component LocationThe fuel pump is located on the back side of the gear housing. Shop TalkThe fuel pump controller disables fuel injection if a greater-than-6-VDC signal is registered at pin 5 (pump connector end) for 1 second. This signal line is triggered if an engine protection limit is exceeded or if a pump controller defect is set.Normal engine operation is as follows:1) 0-VDC at pin 5 at keyswitch ON2) 12-VDC at pin 5 at keyswitch OFF, until ECM powers down.Check for...

Circuit DescriptionThis circuit provides a secondary fuel shutoff signal from the engine control module (ECM) to the fuel pump. Component LocationThe fuel pump is located on the back side of the gear housing. Shop TalkThe fuel pump controller disables fuel injection if a greater-than-6-VDC signal is registered at pin 5 (pump connector end) for 1 second. This signal line is triggered if an engine protection limit is exceeded or if a pump controller defect is set.Normal engine operation is as follows:1) 0-VDC at pin 5 at keyswitch ON2) 12-VDC at pin 5 at keyswitch OFF, until ECM powers down.Check for...

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. Cummins ISB CM550 (1990-94)...