This Cummins fault 3243 document is an 8-page troubleshooting procedure for an engine cooling system monitor fault where coolant temperature remains below the expected operating range. It explains the coolant temperature sensor circuit, fault conditions, diagnostic steps, repair validation, and INSITE™ service-tool actions for Code 3243.
Official Cummins fault 3243 document details
| Brand | Cummins |
|---|---|
| Model coverage | ISX11.9 CM2250, ISX15 CM2250, GX CM2250, QSL9 CM2250, QSB6.7 CM2250; file listing also references ISB6.7 CM2250 (2010-12) |
| System/Group | Engine Cooling System Monitor; coolant temperature sensor circuit; DTCs |
| Publication no. | 4022250, 2883445, 4022256, 4022255 appear in the associated procedures table |
| Year/Revision | Last Modified: 11-Jun-2010 and 06-Dec-2010 |
| Pages | 8 |
| 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 engine fan operation.
- Guided Step 3 – Check the thermostat.
- Guided Step 4 – Check ECM calibration and clear fault codes.
Applicable truck models
The extract lists Cummins ISX11.9 CM2250/ISX15 CM2250 coolant temperature sensor circuit coverage and an associated procedures table for ISX15 CM2250, GX CM2250, ISX11.9 CM2250, QSL9 CM2250, and QSB6.7 CM2250. The file information also places the document in the ISB6.7 CM2250 (2010-12) DTC group, so use this PDF only as indexed and confirm engine family, ECM calibration, and bulletin reference before applying a repair. For manufacturer information, visit Cummins official website.
Who needs this Cummins fault 3243 manual
This manual is for diesel mechanics, fleet technicians, and workshop owners diagnosing an amber CHECK ENGINE lamp or MIL caused by Code 3243. It is most useful when checking coolant warm-up complaints, low coolant level or air in the cooling system, engine fan operation, a leaking or stuck open thermostat, a malfunctioning coolant temperature sensor, or an ECM calibration update.
The procedure describes a variable resistor coolant temperature sensor supplied with 5 volts by the ECM, located on the exhaust side of the engine near the thermostat housing. The diagnostic runs continuously when the engine is running if coolant temperature was less than 52°C [126°F] at engine start, and the fault sets when coolant temperature does not reach 72°C [162°F] within the specified time. The guided checks use INSITE™ electronic service tool to read active fault codes, perform the Fan Override Test, verify thermostat operation under Procedure 008-013, replace the engine coolant temperature sensor under Procedure 019-019 when directed, compare ECM code and revision information, and calibrate the ECM under Procedure 019-032 if needed. Repair validation includes starting the engine, idling for 5 minutes, and confirming that the fault status changes to INACTIVE after the diagnostic runs and passes.
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