This fault code 1656 DTCs document is a troubleshooting procedure for Engine Misfire Cylinder 3 on CM2250 electronic engines. It explains when the diagnostic runs, what sets the amber CHECK ENGINE lamp or MIL, and how to validate repairs with INSITE electronic service tool.
Official fault code 1656 DTCs document details
| Brand | Cummins |
|---|---|
| Model coverage | Indexed as ISB6.7 CM2250; associated procedures list ISX15 CM2250, ISX11.9 CM2250, QSL9 CM2250, and QSB6.7 CM2250 |
| System/Group | DTCs; ECM Circuit; Engine Misfire Cylinder 3 – Condition Exists |
| Publication no. | Not stated in the extract |
| Year/Revision | Last modified 11-Jun-2010 and 20-Jul-2010; file year unknown |
| Pages | 7 |
| 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
- FAULT CODE 1656 Engine Misfire Cylinder 3 – Condition Exists
- 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 – Perform diagnostic tests.
- Guided Step 3 – Check if an ECM calibration update is available.
- Guided Step 3B – Disable the fault code.
Applicable truck models
This file applies to Cummins CM2250 engine diagnostics shown in the extract. The associated procedure table references ISX15 CM2250, ISX11.9 CM2250, QSL9 CM2250, and QSB6.7 CM2250 for injector Procedure 006-026 and ECM Calibration Code Procedure 019-032. The document describes an ECM algorithm that monitors engine speed at idle as each injector fires, then sets the fault when cylinder number 3 has high or low contribution to engine speed. For current manufacturer information, visit the Cummins official website.
Who needs this fault code 1656 DTCs manual
Workshop owners, diesel mechanics, and fleet technicians need this manual when diagnosing rough idle, low power, smoke, stumble, or a misfire complaint tied to cylinder number 3. It is also useful when checking whether inactive counts can be ignored after events such as air entering the fuel system following a filter change.
The procedure directs technicians to read active and inactive fuel system fault codes, confirm whether a cylinder misfire can be detected, run the Cylinder Cutout Test, and decide whether cylinder number 3 injector has been isolated as the failure. If the injector is not confirmed, the document points to other causes such as valve lash out of specification, cylinder malfunction, valve malfunction, cylinder head or gasket damage, extreme camshaft wear, injector sealing washer issues, or mistimed air compressor. The final steps compare the ECM code and revision number against calibration revision history, calibrate the ECM if needed, then operate the engine under the clearing conditions and confirm the fault is inactive.
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