This 6-page Cummins document provides the complete diagnostic and troubleshooting procedure for the Cummins 3612 fault code, which indicates the aftertreatment diesel exhaust fluid (DEF) dosing unit mechanical system is not responding or is out of adjustment. The guide covers circuit description, conditions for setting and clearing the fault, and a step-by-step guided troubleshooting tree for identifying incomplete purge cycle causes on CM2250-controlled engines.
Official Cummins 3612 fault code document details
| Brand | Cummins |
| Model coverage | ISB6.7 CM2250, ISC8.3 and ISL9 CM2250, ISX11.9 CM2250, ISX15 CM2250 |
| System / Group | Aftertreatment Diesel Exhaust Fluid Controller — DTCs |
| Publication no. | Not specified (ECM Calibration Bulletins: 4022254, 4022257, 4022250, 2883445) |
| Year / Revision | Last Modified 10-Jan-2011 |
| Pages | 6 |
| File size | 0.2 MB |
| Format | |
| Language | English |
Document table of contents
- Overview — Circuit Description
- Component Location
- Conditions for Running the Diagnostics
- Fault Code 3612 — Code Reason and Effect (SPN 3361, FMI 7)
- Conditions for Setting the Fault Codes
- Action Taken When the Fault Code is Active
- Conditions for Clearing the Fault Code
- Shop Talk
- Associated Procedures (ECM Calibration Code — Procedure 019-032)
- Guided Step 1 — Check the Fault Codes (1117, 3577, 3578, 3579)
- Guided Step 2 — Check Main Battery Disconnect Switch Operation
- Guided Step 3 — Check ECM Calibration and Clear Fault Codes
- Guided Step 3B — Disable the Fault Code
Applicable truck models
This troubleshooting procedure applies to vehicles equipped with the Cummins ISB6.7 CM2250, ISC8.3 and ISL9 CM2250, ISX11.9 CM2250, and ISX15 CM2250 engine platforms using the aftertreatment diesel exhaust fluid controller and SCR system. The dosing unit location is OEM dependent, so the document directs technicians to the relevant OEM service manual for physical mounting details. Fault code 3612 is classified as SPN 3361, FMI 7 and carries no warning lamp. The SCR purge cycle requires battery power for at least 60 seconds after key OFF; vehicles with automatic battery disconnect switches must incorporate a built-in delay device. For additional Cummins service resources, visit the official Cummins website.
Who needs this Cummins 3612 fault code manual
Diesel technicians and workshop owners dealing with repeated incomplete DEF purge cycles on CM2250-equipped trucks need this document. It is essential for anyone using the INSITE™ electronic service tool to reset purge counters, verify ECM calibration revisions, and clear stored fault codes after confirming correct battery disconnect switch operation.
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