This Cummins 1668 troubleshooting manual is a fault-code diagnostic document for the aftertreatment diesel exhaust fluid tank level sensor circuit. It covers Fault Code 1668, PID P203C, SPN 1761, FMI 4, including 2-wire and 3-wire sensor paths. The procedure explains low signal voltage checks, connector inspections, harness tests, ECM calibration review, and fault clearing with INSITE™.
Official Cummins 1668 troubleshooting manual document details
| Brand | Cummins |
|---|---|
| Model coverage | ISB6.7 CM2250; also references ISX11.9 CM2250, ISC8.3 and ISL9 CM2250, and ISX15 CM2250 in the extracted procedure tables |
| System/Group | ISB6.7 CM2250 (2010-12) / DTCs; aftertreatment diesel exhaust fluid tank level sensor circuit |
| Publication no. | Associated bulletin numbers shown: 4022254, 4022257, 4022250, 2883445 |
| Year/Revision | Last Modified: 03-Mar-2010, 23-Nov-2010, and 11-Jun-2010 shown in extract; year otherwise unknown |
| Pages | 30 |
| File size | 0.6 MB |
| Format | |
| Language | English |
Document table of contents
- Fault Code Path Selection
- Overview
- Circuit Description
- Component Location
- Conditions for Running the Diagnostics
- FAULT CODE 1668 (2-Wire Sensor) – Aftertreatment Diesel Exhaust Fluid Tank Level Sensor Circuit – Voltage Below Normal or Shorted to Low Source
- Conditions for Setting the Fault Codes
- 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 aftertreatment diesel exhaust fluid tank level sensor and circuit
- Guided Step 3 – Check the aftertreatment diesel exhaust fluid controller and harness
- Guided Step 4 – Check ECM calibration and clear fault codes
- FAULT CODE 1668 (3-Wire Sensor) – Aftertreatment Diesel Exhaust Fluid Tank Level Sensor Circuit – Voltage Below Normal or Shorted to Low Source
- Guided Step 2B – Check the sensor supply voltage and return circuit
- Guided Step 3B – Check for an open circuit in the OEM harness
Applicable truck models
This file applies to Cummins CM2250 engine diagnostics shown in the extract: ISB6.7 CM2250, ISX11.9 CM2250, ISC8.3 and ISL9 CM2250, and ISX15 CM2250. The DEF tank and level sensor location is OEM dependent, so the document directs users to the OEM service manual for vehicle-specific component location while the diagnostic logic remains focused on the aftertreatment diesel exhaust fluid tank level sensor circuit. Manufacturer information is available from Cummins official website.
Who needs this Cummins 1668 troubleshooting manual manual
Workshop owners, diesel technicians, and fleet mechanics need this Cummins 1668 troubleshooting manual when an amber CHECK ENGINE lamp is active and the SCR system disables diesel exhaust fluid injection. It is useful for diagnosing a low-voltage or short-to-low-source condition, inspecting dirty or damaged pins, checking resistance greater than 100k ohms, verifying Fault Code 3557 where applicable, and deciding whether an ECM calibration update is required.
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