This code 429 DTCs document is a troubleshooting manual for the water-in-fuel indicator sensor circuit on CM2250 engines. It explains the low-voltage or short-to-low-source condition, ECM response, INSITE™ checks, connector inspections, harness tests, calibration review, and fault clearing.
Official code 429 DTCs document details
| Brand | Cummins |
|---|---|
| Model coverage | ISB6.7 CM2250, with associated coverage listed for ISC8.3 and ISL9 CM2250, ISX15 CM2250, ISX11.9 CM2250, QSL9 CM2250, QSB6.7 CM2250, and other Cummins CM engines shown in the associated procedures table. |
| System/Group | ISB6.7 CM2250 (2010-12) / DTCs; water-in-fuel sensor circuit |
| Publication no. | 4022254 for ISB6.7 CM2250 in the associated procedures table |
| Year/Revision | Last modified 11-Jun-2010 and 20-Jul-2010; file year unknown |
| Pages | 15 |
| File size | 0.3 MB |
| Format | |
| Language | English |
Document table of contents
- Overview
- Circuit Description
- Component Location
- Conditions for Running the Diagnostics
- 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 2 – Check the water-in-fuel sensor.
- Guided Step 3 – Check the engine harness.
- Guided Step 4B – Disable the fault code.
Applicable truck models
The document applies to Cummins electronic engine platforms listed in the procedure table, including ISB6.7 CM2250 and related CM2250 engines where Fault Code 429 is used for the water-in-fuel indicator sensor circuit. The extract identifies the sensor as integrated into the bottom of the OEM-supplied suction fuel filter, so vehicle installation depends on the OEM fuel filter arrangement. For manufacturer information, visit Cummins official website.
Who needs this code 429 DTCs manual
This manual is for diesel mechanics, fleet technicians, and workshop owners diagnosing an amber CHECK ENGINE light with SPN 97 FMI 4/4 and no water-in-fuel warning available. It is useful when checking whether the fault comes from the sensor, connector pins, engine wiring harness, ECM response, or ECM calibration.
The troubleshooting flow starts with confirming whether Fault Code 429 is active using INSITE™ electronic service tool. It then directs the technician through water-in-fuel sensor connector inspection, ECM response checks after disconnecting the sensor, and replacement of a damaged water-in-fuel sensor when the circuit behavior confirms the sensor fault. Later steps inspect the ECM connector and engine harness connector for dirty or damaged pins, wire insulation damage, and damaged connector locking tabs.
The harness tests include pin-to-pin short circuit checks and pin-to-ground short circuit checks on the SIGNAL line, with the extract showing a greater than 100k ohms pass criterion. If the ECM response does not match the expected active Fault Code 428 and inactive Fault Code 429 condition during a guided check, the procedure can lead to authorization for ECM replacement. The final section checks whether an ECM calibration update related to this fault code is available, then uses the stated clearing conditions to disable and clear the code.
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