The Cummins ISM code 393 manual is a 5-page diagnostic PDF for the engine brake supply circuit on the ISM CM570 (1999–2002) engine. It documents the engine brake supply circuit that the electronic control module (ECM) drives to enable the engine brakes under set operating conditions.
Cummins ISM code 393 document details
| Brand | Cummins |
| Model coverage | ISM CM570 (1999–2002) |
| System / group | Engine brake supply circuit — DTCs |
| DTC number | 393 |
| PID / SPN | S082 / 1112 |
| FMI | 11/11 |
| Warning lamp | YELLOW |
| Pages | 5 |
| File format | |
| Language | English |
Document table of contents
- Circuit description and component location
- Shop talk on circuit-3 short to ground
- Actuator harness and ECM pin inspection
- Engine-brake 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 393 manual
The document places the engine brakes under the valve cover and states that the ECM enables them only under certain operating conditions. The listed cause for this fault is a short circuit to ground on ECM engine brake circuit 3. The steps inspect the actuator harness and ECM connector pins for looseness, corrosion, bent pins, broken shells, damaged insulation and locking tabs, flush contacts with electrical contact cleaner Part Number 3824510, and then measure engine-brake circuit resistance before calling for authorisation to replace parts.
This guide suits diesel technicians and workshop owners who face a fault on engine brake circuit 3 and want the connector inspection and resistance checks before parts authorisation. It reads as fault code 393 troubleshooting steps for the engine brake supply circuit, keeping the diagnosis ordered and evidence-based.
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