This 12-page PDF is a fault code 3681 DTCs troubleshooting guide covering the aftertreatment outlet NOx sensor power supply diagnostic for CM2250-controlled engines. It provides the fault code definition (SPN 3228, FMI 2), conditions for running and clearing the diagnostic, shop talk on probable causes, and a complete guided troubleshooting tree from Step 1 through Step 4.
Official fault code 3681 DTCs document details
| Brand | Cummins |
| Model coverage | ISB6.7 CM2250, ISC8.3 and ISL9 CM2250, ISX15 CM2250, ISX11.9 CM2250, GX CM2250, ISF2.8 CM2220, ISF3.8 CM2220 |
| System / Group | Aftertreatment — Diagnostic Trouble Codes (DTCs) |
| Publication no. | — |
| Year / Revision | Last modified 27-Dec-2010 |
| Pages | 12 |
| File size | 0.2 MB |
| Format | |
| Language | English |
Document table of contents
- Overview — Circuit Description, Component Location
- Fault Code 3681 — Aftertreatment Outlet NOx Sensor Power Supply: Data Erratic, Intermittent, or Incorrect (PID P411, SPN 3228, FMI 2)
- Conditions for Running the Diagnostics
- Conditions for Setting the Fault Code
- Conditions for Clearing the Fault Code
- Shop Talk — Possible Causes
- Associated Procedures — ECM Calibration Code (Procedure 019-032), Aftertreatment Outlet NOx Sensor (Procedure 019-451)
- Guided Step 1 — Check the Fault Codes (1A, 1B)
- Guided Step 2 — Check the Aftertreatment Outlet NOx Sensor Circuit (2A through 2E)
- Guided Step 3 — Check the OEM Harness (3A, 3B)
- Guided Step 4 — Check ECM Calibration and Clear Fault Codes (4A, 4B)
Applicable truck models
The document applies to multiple Cummins engine platforms using the CM2250 and CM2220 electronic control modules. Primary coverage is the ISB6.7 CM2250 (2010–2012), but the troubleshooting tree and associated procedure references also list the ISC8.3, ISL9, ISX15, ISX11.9, and GX CM2250 as well as the ISF2.8 and ISF3.8 CM2220. The NOx sensor is noted as available in 12-volt and 24-volt versions, depending on the vehicle electrical system. The aftertreatment outlet NOx sensor is typically located at the outlet of the SCR catalyst in the exhaust system. For official engine documentation visit Cummins official website.
Who needs this fault code 3681 DTCs manual
Diesel mechanics and workshop owners diagnosing an amber CHECK ENGINE or MIL lamp triggered by fault code 3681 will use this guide to systematically isolate the root cause — whether it is a short to battery or ground in the OEM harness, an open NOx sensor power supply circuit, incorrect system voltage parameter settings in INSITE™, or an internal sensor malfunction.
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