Cummins fault code 238 is documented on this DiagTechPro library page for Cummins ISM CM871 (2007-09) engines, where it flags a Sensor Supply 3 Circuit – Voltage Below Normal Or Shorted To Low Source condition (PID S232, SPN 3511, FMI 4/4, Amber lamp). This 3-page PDF reproduces the manufacturer description, shop talk, component location and step-by-step troubleshooting so technicians can confirm and clear the code.
Cummins fault code 238 overview
Cummins defines this code as “SENSOR SUPPLY 3 CIRCUIT – VOLTAGE BELOW NORMAL OR SHORTED TO LOW SOURCE” on the Engine Speed Sensor Supply 3 Circuit. The sensor supply 3 circuit provides 5-volt supply to the primary engine speed/position sensor. Component location: The engine speed sensor is located in the lower portion of the front cover on the intake side of the engine. Read the code with a diagnostic tool, confirm it is active, and follow the numbered troubleshooting steps before replacing any component.
Shop talk notes: Verify the electronic control module (ECM) calibration is correct. If necessary, recalibrate the ECM. The ECM monitors the voltage level on the engine speed sensor +5-volt supply circuit.
Official document details
| Brand | Cummins |
| Model coverage | Cummins ISM CM871 (2007-09); Cummins ISX CM871 (2007-09) |
| System / Group | Engine Speed Sensor Supply 3 Circuit — ISM CM871 fault codes |
| Fault code | 238 (SPN 3511, FMI 4/4) |
| Source | TruckFaultCodes.com Cummins fault code reference (© 2017) |
| Pages | 3 |
| File size | 0.1 MB |
| Format | |
| Language | English |
Document table of contents
- Fault code identification (PID, SPN, FMI, lamp)
- Description
- Shop Talk
- Component Location
- Troubleshooting Steps
Applicable truck models and engines
This document applies to Cummins ISM CM871 (2007-09); Cummins ISX CM871 (2007-09) equipped diesel engines that log Fault Code 238. Always confirm engine calibration and use a Cummins diagnostic tool such as INSITE to read live data before starting repairs. Full specifications are published on the Cummins official website.
Who needs this Cummins fault code 238 manual
Heavy-duty truck technicians, fleet workshops and owner-operators diagnosing an electronic control module warning on ISM CM871 engines will use this sheet to verify the fault before parts are replaced.
The full PDF is available in the DiagTechPro manuals library; a free account is required to download.
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