The Cummins ISM code 378 manual is a 5-page diagnostic PDF for the actuator circuit on the ISM CM570 (1999–2002) engine. It covers the front fueling actuator that the electronic control module (ECM) pulses to meter fuel from the fuel delivery housing.
Cummins ISM code 378 document details
| Brand | Cummins |
| Model coverage | ISM CM570 (1999–2002) |
| System / group | Actuator circuit — DTCs |
| DTC number | 378 |
| PID / SPN | S018 / 633 |
| FMI | 5/5 |
| Warning lamp | YELLOW |
| Pages | 5 |
| File format | |
| Language | English |
Document table of contents
- Circuit description and component location
- Shop talk on open-circuit failure modes
- Actuator harness pin inspection
- Actuator resistance measurement
Applicable truck models
This procedure applies to the ISM CM570 (1999–2002) engine and the shared CM570 fuel-system platform found in on-highway trucks. The same fault-code logic is carried across related CM570 engine families of that era. For engine identification and factory service references, see the manufacturer at the Cummins official website.
Who needs this Cummins ISM code 378 manual
The document explains that each fuel actuator connects to the ECM through a supply and a return wire, with the normally closed solenoid opening only on an electrical pulse during metering. It places the front fueling actuator as the one closest to the front of the engine. For this fault the listed failure modes are an open circuit, a short to ground, high actuator resistance, a supply wire shorted to battery, and loss of boost voltage inside the ECM. The steps inspect the actuator harness connector pins before measuring resistance.
This guide suits diesel technicians and workshop owners who face a front fueling actuator open-circuit or short-to-battery fault and want the ordered wiring and resistance checks. It reads as fault code 378 troubleshooting steps for the actuator circuit, keeping the diagnosis ordered and evidence-based.
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