Cummins ISM code 1843 is the Cummins ISM CM871 (2007-09) diagnostic reference for fault code 1843, the crankcase pressure sensor DTC that is logged when the crankcase pressure circuit reads above normal or shorts to a high source. This 5-page PDF from the Cummins ISX and ISM Troubleshooting and Repair documentation lists the fault identifiers, component description, and step-by-step checks. It carries PID P101, SPN 101, FMI 3/3, and lights Amber warning lamp.
Official document details
| Brand | Cummins |
| Model coverage | ISM CM871 (2007-09) and ISX CM871 engines |
| System / group | ISM CM871 (2007-09) / DTCs |
| Fault code | 1843 — SPN 101, FMI 3/3, PID P101 |
| Warning lamp | AMBER |
| Pages | 5 |
| File size | 0.2 MB |
| Format | |
| Language | English |
Document table of contents
- Fault code identification (PID, SPN, FMI, warning lamp)
- Description
- Shop Talk
- Component location
- Troubleshooting steps
Cummins ISM code 1843 diagnosis
Fault code 1843 is logged when the crankcase pressure circuit reads above normal or shorts to a high source. The crankcase pressure sensor monitors pressure inside the crankcase gas filter assembly and a code is logged when that pressure reaches a maximum level, signalling that the crankcase filter needs maintenance. The sensor shares supply and return wires with other sensors. According to the Cummins Shop Talk guidance, technicians should first verify that the ECM calibration is correct and recalibrate if necessary before component replacement. Possible causes listed in the document include:
- An open return circuit in the engine harness, connectors, or sensor.
- A signal wire shorted to sensor supply or battery voltage.
Applicable truck models and engines
This document applies to Cummins ISM CM871 (2007-09) engines and the closely related ISX CM871 platform used in on-highway trucks, so it suits heavy-duty tractors and vocational trucks fitted with these engines and their aftertreatment systems. Always confirm the engine dataplate and refer to the OEM troubleshooting and repair manual for chassis-specific pin numbers. Full specifications are published on the Cummins official website.
Who needs this Cummins ISM code 1843 manual
Diesel technicians, fleet mechanics, and workshop owners diagnosing the crankcase pressure sensor on ISM CM871 engines will use this reference to read the fault identifiers correctly and follow the factory test sequence for code 1843.
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