The Cummins ISM code 394 manual is a 6-page diagnostic PDF for the actuator circuit on the ISM CM570 (1999–2002) engine. It covers the front timing actuator that the electronic control module (ECM) pulses to control fuel metering on the fuel delivery housing.
Cummins ISM code 394 document details
| Brand | Cummins |
| Model coverage | ISM CM570 (1999–2002) |
| System / group | Actuator circuit — DTCs |
| DTC number | 394 |
| PID / SPN | S020 / 635 |
| FMI | 5/5 |
| Warning lamp | YELLOW |
| Pages | 6 |
| File format | |
| Language | English |
Document table of contents
- Circuit description and component location
- Shop talk on open-circuit failure modes
- Actuator harness and ECM 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 394 manual
The document explains that each timing actuator connects to the ECM through a supply and a return wire and that the normally closed solenoid opens only on an electrical pulse during metering. It places the front timing actuator as the second actuator from the front of the engine. For this fault the listed failure modes are an open circuit, a short to ground, high actuator resistance, and loss of boost voltage inside the ECM. The steps inspect the actuator harness and ECM connector pins in detail before measuring resistance.
This guide suits diesel technicians and workshop owners who face a front timing actuator open-circuit or high-resistance fault and want the connector and resistance sequence. It reads as fault code 394 troubleshooting steps for the actuator circuit, keeping the diagnosis ordered and evidence-based.
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