This fault code 238 DTCs document is a troubleshooting guide for the sensor supply 3 circuit on CM2150-equipped Cummins engines. It explains the low-voltage fault, the ECM response, connector checks, INSITE™ service tool steps, and final fault clearing procedure.
Official fault code 238 DTCs document details
| Brand | Cummins |
|---|---|
| Model coverage | ISB6.7 CM2150 (2007-09); ISB, ISC, ISL with CM2150 as stated in the extract |
| System/Group | DTCs; Engine Speed Sensor Supply 3 Circuit |
| Year/Revision | Last Modified: 20-Jul-2010 |
| Pages | 9 |
| File size | 0.2 MB |
| Format | |
| Language | English |
Document table of contents
- Overview
- Circuit Description
- Component Location
- Conditions for Running the Diagnostics
- Conditions for Setting the Fault Codes
- FAULT CODE 238
- Action Taken When the Fault Code is Active
- Conditions for Clearing the Fault Code
- Shop Talk
- Associated Procedures
- Troubleshooting Steps
- Guided Step 1 – Check the fault codes.
- Guided Step 2 – Check the sensors and circuits connected to the sensor supply and return.
- Guided Step 3 – Check the ECM.
- Guided Step 4 – Clear the fault codes.
Applicable truck models
This PDF applies to Cummins ISB6.7 CM2150 (2007-09) fault-code diagnostics and also references ISB, ISC, ISL with CM2150 for the Engine Speed Sensor Supply 3 Circuit. The document covers the primary engine speed/position sensor supply circuit, the engine speed sensor in the lower portion of the front cover on the intake side of the engine, and the ECM monitoring logic for the +5 volt sensor supply circuit. For manufacturer information, visit Cummins official website.
Who needs this fault code 238 DTCs manual
Workshop owners, diesel mechanics, and fleet technicians need this fault code 238 DTCs manual when an amber CHECK ENGINE light is active and INSITE™ shows SPN: 3511 FMI: 4/4. It is useful for diagnosing hard starting, rough running, short-to-ground conditions, harness damage, dirty pins, connector seal problems, or possible ECM-related circuit response issues.
The troubleshooting flow starts by confirming whether Fault Code 238 is active with INSITE™ electronic service tool. It then directs the technician to inspect the engine speed sensor connector, engine harness connector pins, ECM connector pins, wiring insulation, locking tabs, connector shells, moisture, debris, corrosion, bent pins, pushed-back pins, expanded pins, and damaged seals. If the code response changes after disconnecting the engine speed sensor, the guide points to replacing the engine speed sensor. If the code remains active during ECM-side checks, the procedure moves toward ECM authorization or engine harness repair, depending on the circuit response.
The guide also lists related Cummins procedures, including Procedure 019-362 for inactive or intermittent fault codes, Procedure 019-361 for component connector and pin inspection, Procedure 019-043 for the engine wiring harness, Procedure 019-042 for the Engine Speed Sensor (ESS), Procedure 019-031 for the Electronic Control Module (ECM), and Procedure 019-032 for ECM calibration code review. The final steps reconnect all components, run the engine at idle for 1 minute, verify the fault code is inactive, and erase inactive fault codes.
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