This fault code 2398 DTCs document is a troubleshooting PDF for an ambient air temperature sensor fault on CM2250 engines. It explains the circuit description, diagnostic conditions, fault effects, guided tests, connector inspections, ECM harness checks, calibration review, and fault-code clearing steps for workshop use.
Official fault code 2398 DTCs document details
| Brand | Cummins |
|---|---|
| Model coverage | ISX11.9 CM2250, ISX15 CM2250, GX CM2250; file group lists ISB6.7 CM2250 (2010-12) / DTCs |
| System/Group | Ambient Air Temperature Sensor 1 Circuit / DTCs |
| Publication no. | Associated procedure bulletins shown: 4022250 and 2883445 |
| Year/Revision | Last Modified: 11-Jun-2010 and 29-Dec-2010 |
| Pages | 12 |
| 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 for sensor circuit fault codes.
- Guided Step 2 – Check the ambient air temperature sensor and circuit.
- Guided Step 3 – Check the ECM and engine harness.
- Guided Step 4 – Check ECM calibration and clear fault codes.
Applicable truck models
The extract identifies this procedure for ISX11.9 CM2250, ISX15 CM2250, and GX CM2250 engine applications, with file grouping also listing ISB6.7 CM2250 (2010-12) / DTCs. The ambient air temperature sensor mounting location is OEM dependent, so the document directs users to the appropriate OEM service manual for physical location details. See the manufacturer site at Cummins official website.
Who needs this fault code 2398 DTCs manual
This manual is for diesel mechanics, fleet technicians, and workshop owners diagnosing an amber CHECK ENGINE lamp or MIL caused by SPN 171 FMI 2. It is useful when INSITE™ shows Ambient Air Temperature – Data Erratic, Intermittent, or Incorrect and the ECM is estimating ambient air temperature.
The procedure describes how the ECM supplies 5 volts to the ambient air temperature signal circuit and monitors voltage changes caused by sensor resistance. It lists likely causes, including a stuck in-range ambient air temperature sensor, high resistance in the signal or return lines, and possible ECM malfunction. The guided steps use INSITE™ electronic service tool checks for active fault codes, including Fault Code 249 and Fault Code 256, before moving into sensor connector and circuit-response testing.
Later steps cover inspection points that matter in real service bays: loose connectors, corroded pins, bent or broken pins, pushed-back or expanded pins, moisture, missing connector seals, damaged wiring insulation, and broken locking tabs. The workflow then checks the ECM and engine harness connectors, uses jumper-wire circuit response tests at the sensor connector and ECM connector, and identifies when to repair the engine harness, replace the ambient air temperature sensor, or call for authorization to replace the ECM.
The final section explains calibration review and clearing. It instructs the technician to compare the ECM code and revision number with the calibration revision history, calibrate the ECM if needed, then operate the engine within the clearing conditions. To validate repair, the summary states that the engine may need a 1-minute idle check or a 10 hour cold soak with the key OFF before the key ON diagnostic can run.
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