The Cummins ISM code 422 manual is a 11-page diagnostic PDF for the coolant level sensor circuit on the ISM CM570 (1999–2002) engine. It documents the coolant level sensor in the radiator or surge tank, which reports coolant level to the electronic control module (ECM) through the sensor harness.
Cummins ISM code 422 document details
| Brand | Cummins |
| Model coverage | ISM CM570 (1999–2002) |
| System / group | Coolant level sensor circuit — DTCs |
| DTC number | 422 |
| PID / SPN | P111 / 111 |
| FMI | 2/2 |
| Warning lamp | YELLOW |
| Pages | 11 |
| File format | |
| Language | English |
Document table of contents
- Circuit description and component location
- Shop talk on open and short circuits
- Code 187 and sensor-present checks
- Shorting plug and harness wiring diagrams
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 422 manual
The document warns that the sensor is complex and must not be checked with a multimeter, and that a coolant level below a set point causes a power derate that grows over time. Listed causes are an open circuit, a short to ground, or a short to another wire. The eleven-page tree first confirms Code 187 is inactive, checks whether the sensor is present, verifies the shorting plug where no sensor is fitted, and works through the OEM and engine-harness wiring diagrams.
This guide suits diesel technicians and workshop owners who face a coolant-level derate and need the shorting-plug logic and wiring-diagram references for the radiator sensor. It reads as fault code 422 troubleshooting steps for the coolant level sensor circuit, keeping the diagnosis ordered and evidence-based.
The full PDF is available in the DiagTechPro manuals library, where a free account is required to download it.
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