Cummins ISM code 121 is the DiagTechPro reference page for this Cummins diagnostic fault code 121 document, a 6-page PDF sourced from TruckFaultCodes.com (Copyright 2017) that covers the crankshaft engine position sensor circuit. The crankshaft engine position sensor provides engine speed and position information to the electronic control module (ECM). The sensor must be powered up by (+) 5-VDC to operate. The sensor generates the signal by sensing the movement of target teeth machined into a tone wheel that is mounted to the crankshaft. When the condition is detected the ECM logs the fault and turns on the yellow warning lamp to alert the driver and technician.
Cummins ISM code 121 document details
| Brand | Cummins |
|---|---|
| Model coverage | ISM CM570 (1999-02) / DTCs; ISX CM570 (1999-02) / DTCs; Signature CM570 (1999-02) / DTCs |
| System / Group | ISM CM570 (1999-02) / DTCs |
| Fault identifier | Code 121 (PID P190, SPN 190, FMI 10) |
| Warning lamp | Yellow |
| Source | TruckFaultCodes.com |
| Year / Revision | Copyright 2017 |
| Pages | 6 |
| File size | 0.4 MB |
| Format | |
| Language | English |
Document table of contents
- Circuit Description
- Component Location
- Shop Talk
- Troubleshooting Steps
- Repair verification and clearing fault codes
Applicable truck models
This document applies to Cummins ISM CM570 (1999-02) / DTCs; ISX CM570 (1999-02) / DTCs; Signature CM570 (1999-02) / DTCs electronic engines used in on-highway and vocational trucks. The crankshaft engine position sensor is located on the side of the front cover on the intake side of the engine. The troubleshooting section walks through connector and pin inspection, engine-harness resistance measurements and pin-to-pin continuity checks, and ends with a road test that confirms the code is inactive and all fault codes are cleared. Because the same procedure isolates the sensor, the harness and the ECM in turn, it prevents replacing parts that are still good. Verify engine calibration and coverage against the official Cummins engine support site before ordering parts.
Who needs this Cummins ISM code 121 manual
Any mechanic or workshop owner diagnosing ISM code 121 needs this PDF to follow the factory circuit and resistance checks in the correct order. Possible causes of this fault code include a damaged crankshaft engine position sensor, an open or a short circuit, or power supply voltage failure. 2.
Related manuals library
The full PDF is available in the DiagTechPro manuals library; a free account is required to download.
