The Cummins ISM code 442 manual is a 2-page diagnostic PDF for the unswitched battery supply circuit on the ISM CM570 (1999–2002) engine. It covers the high-voltage side of the unswitched battery feed to the electronic control module (ECM), where charging-system or aftermarket-wiring faults drive the reading out of range.
Cummins ISM code 442 document details
| Brand | Cummins |
| Model coverage | ISM CM570 (1999–2002) |
| System / group | Unswitched battery supply circuit — DTCs |
| DTC number | 442 |
| PID / SPN | P168 / 168 |
| FMI | 0/16 |
| Warning lamp | YELLOW |
| Pages | 2 |
| File format | |
| Language | English |
Document table of contents
- Circuit description and component location
- Shop talk notes
- Battery voltage measurement while cranking
- Alternator and charging referral to OEM manual
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 442 manual
The two-page document notes that the ECM is fed by two in-line 15-amp fuses and grounded directly to the negative battery post. Its shop-talk section tells the technician to disconnect all aftermarket devices from the battery supply circuit and confirm the correct 15-amp fuses are fitted. The single troubleshooting step measures battery voltage from the positive to negative terminal while cranking (at least 12 VDC normally, 6.2 VDC cranking) and then refers to the OEM manual for alternator and charging checks.
This guide suits diesel technicians and workshop owners who face an over-voltage battery-supply fault and need to isolate a charging or aftermarket-wiring cause quickly. It reads as fault code 442 troubleshooting steps for the unswitched battery supply 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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