Cummins ISM Code 388 is the official Cummins fault code troubleshooting PDF that documents the engine brake supply circuit on ISM CM570 (1999-02) engines. This 6-page reference from the Cummins service literature explains the circuit, the likely causes behind the yellow warning lamp, and the step-by-step checks a technician follows to confirm the repair.
Official document details
| Brand | Cummins |
|---|---|
| Model coverage | ISM CM570, ISX CM570 and Signature CM570 (1999-02) |
| System / Group | Engine Brake Supply Circuit (DTCs) |
| Fault code | Code 388 · PID S079 · SPN 1072 · FMI 11/11 |
| Warning lamp | Yellow |
| Year / Revision | Copyright 2017 |
| Pages | 6 |
| File size | 0.4 MB |
| Format | |
| Language | English |
Document table of contents
- Circuit description
- Component location
- Shop talk – possible causes
- Troubleshooting steps
- Fault code verification and clearing
Cummins ISM Code 388 troubleshooting summary
The electronic control module (ECM) enables the engine brake by sending a signal directly to the engine brakes. The ECM will only enable the engine brakes under certain operating conditions. The engine brakes are located under the valve cover. The manual walks through 9 labelled troubleshooting steps that inspect connectors and pins, measure circuit resistance, and verify the fault code is inactive after the repair.
Possible causes listed in the Shop Talk section include:
- ECM engine brake circuit 1 shorted to ground
- This fault code is not used when a three-level engine
Referenced Cummins service tools and part numbers: 3824510, 3162991.
Applicable truck models
This procedure applies to Cummins ISM CM570, ISX CM570 and Signature CM570 engines built in the 1999-02 range, as used in Class 8 highway trucks. Always confirm the exact engine dataplate before servicing. Full engine specifications and dealer support are available on the Cummins official website.
Who needs this Cummins ISM Code 388 manual
Heavy-duty diesel technicians, fleet service managers and independent workshop owners diagnosing a Code 388 on the engine brake supply circuit rely on this document to follow the manufacturer procedure instead of guessing at parts. Because Code 388 shares its troubleshooting logic with the ISX CM570 and Signature CM570 platforms, a single PDF supports several Cummins engine families in the same workshop.
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