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Engine running rough, misfires

Updated: 2026-11-10

The electronics count misfires per cylinder, so the code names the culprit directly. Most often it is an injector, less often compression or wiring. Do not keep driving like this — unburned fuel goes into the exhaust and fouls the catalyst along with the particulate filter.

How to approach it

A misfire means one or more cylinders are not firing; it is felt as a stumble at idle. First use the codes and their description to find out whether one cylinder or several are affected. Then look at the fuel side: injectors, filter and pressure. If the misfire starts under load and gets worse, stop before the catalytic converter is damaged. Fuel and timing codes often come as a group.

The reference does not mark any code in this group as a reason to stop.

These codes usually come with it: SPN 1324, SPN 652, SPN 653, SPN 655.

Other codes for this system

What happens if you keep driving

Time you have: To the nearest safe stop

Fuel is not arriving in the right amount or at the right pressure. It shows up first on climbs and under load.

You will most likely stall out on the road, and may not restart on the shoulder. A clogged filter or water in the tank you can nurse to a shop; a failing injection pump you cannot.

That said, the manufacturer flags this code as critical — if in doubt, it is safer to stop and check on the spot.

What to check on the spot

Check the fuel filter and water trap, drain the water. In cold weather, suspect fuel waxing.

Can I keep driving

The answer depends on the code, not the light. A yellow light is a warning; a red one means do not move. But even under a yellow light there are faults that require stopping right away — low oil pressure, overheating, lost brake pressure. Enter the code — the reference will tell you plainly whether to keep driving or stop.

Know the code number? Type it into the search — or paste the whole list from the scanner and we will show which fault is the real one.