The fault code 338 DTCs troubleshooting manual is the official Cummins diagnostic procedure for the idle shutdown vehicle accessories relay driver circuit on the ISX11.9 CM2250 engine platform. The ECM idle-shutdown feature can drive a shutdown accessory relay; when the parameter is set to Installed the ECM energizes the relay to switch vehicle accessories. This 13-page PDF walks a technician from symptom to verified repair.
Official document details
| Brand | Cummins |
|---|---|
| Model coverage | Cummins ISX11.9 CM2250 (2010-12), Cummins ISX12 CM2250 (2010-12) |
| System / Group | idle shutdown vehicle accessories relay driver circuit, DTCs |
| Fault code reference | Fault Code 338 — SPN 1267, FMI 3 |
| Warning lamp | an amber warning lamp |
| Revision (Last Modified) | 11-Jun-2010 |
| Pages | 13 |
| File size | 0.24 MB |
| Format | |
| Language | English |
fault code 338 DTCs document contents
- Overview and Circuit Description
- Component Location
- Conditions for Running the Diagnostics
- Conditions for Setting the Fault Code
- Action Taken When the Fault Code Is Active
- Conditions for Clearing the Fault Code
- Shop Talk and possible causes
- Associated Procedures table
- Guided troubleshooting steps
- Verify the repair
Applicable truck models covered
This procedure applies to Cummins engines that report Fault Code 338 (SPN 1267, FMI 3), including the Cummins ISX11.9 CM2250 (2010-12), Cummins ISX12 CM2250 (2010-12). Always confirm the exact calibration and publication for your engine on the official Cummins engine support site before ordering parts.
Common causes and symptoms
This fault is logged when the relay driver circuit voltage is above normal or shorted to a high source, so the accessory shutdown function may not operate correctly. Shop Talk in the document lists the most likely causes:
- Relay driver circuit open or shorted to a high source
- A failed accessory shutdown relay or its wiring
Who needs the fault code 338 DTCs manual
Diesel technicians and workshop owners diagnosing Fault Code 338 on ISX11.9 CM2250 trucks need this manual to follow the guided steps, use the correct connector pins and verify the repair with INSITE electronic service tool instead of guessing.
The full PDF is available in the DiagTechPro manuals library; a free account is required to download.
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