This Cummins lift pump fault document is a troubleshooting procedure for Fault Code 2266 on CM2250 midrange engines. It explains the electric fuel lift pump supply circuit, the warning lamp effect, possible short-to-low causes, and the guided diagnostic checks used with INSITE™ electronic service tool.
Official Cummins lift pump fault document details
| Brand | Cummins |
|---|---|
| Model coverage | ISB6.7 CM2250 (2010-12) / DTCs; associated procedures list ISC8.3 and ISL9 CM2250, ISX11.9 CM2250, QSL9 CM2250, and QSB6.7 CM2250 |
| System/Group | Electric Lift Pump for Engine Fuel Supply Circuit – Voltage Below Normal or Shorted to Low Source |
| Publication no. | 4022257, 2883445, 4022256, 4022255 |
| Year/Revision | Last Modified: 20-Jul-2010 |
| Pages | 13 |
| File size | 0.2 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 1 – Check the fault codes.
- Guided Step 2 – Check the electric fuel lift pump.
- Guided Step 3 – Check the engine harness.
- Guided Step 4 – Check ECM calibration and clear fault codes.
Applicable truck models
This file applies to Cummins CM2250 midrange diagnostic coverage shown in the document, including ISB6.7 CM2250 and the associated engine models ISC8.3 and ISL9 CM2250, ISX11.9 CM2250, QSL9 CM2250, and QSB6.7 CM2250. It is written around Fault Code 2266, PID S126, SPN 1075, FMI 4, where the ECM detects low signal voltage at the electric fuel lift pump circuit and disables the pump to protect the driver. For manufacturer information, visit Cummins official website.
Who needs this Cummins lift pump fault manual
Workshop owners, diesel mechanics, and electrical diagnostic technicians need this manual when a truck is difficult to start and INSITE™ shows Fault Code 2266. The procedure helps confirm whether the issue is at the fuel lift pump, connector pins, engine harness, ECM response, calibration level, or a short circuit to ground.
The diagnostic flow covers key ON testing, connector inspection, circuit response checks, pin-to-pin resistance tests, pin-to-ground resistance tests, and ECM calibration review. It also notes field causes such as corroded pins, damaged seals, pushed-back terminals, wire insulation damage, low resistance in the lift pump, and gelled fuel during cold ambient temperatures below -29°C [-20°F]. Full PDF available in the DiagTechPro manuals library, free account required to download.
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