I replaced the coil and plug, but I'm still experiencing rough idling and the error code P0356

I replaced a coil on cylinder two due to a misfire code, and that code cleared up and the problem stopped. However, as soon as I did that (immediately upon starting it up after replacing the offending coil), I got the P0356 error, “Ignition Coil “F” Primary/Secondary Circuit.”

I then replaced the plug and the coil on that cylinder, but I still have the problem and error code.

Could this be an ECU problem?


Hey there,

The P0356 error code you’re encountering is related to a malfunction in the “Ignition Coil F Primary/Secondary Circuit.” This usually indicates an issue with the ignition coil, wiring, or connections. Since you’ve replaced the plug and coil for that cylinder and the error persists, it’s possible that the problem could be with the ECU (Engine Control Unit).

A faulty ECU can cause a variety of issues, including engine misfires, stalling, and erratic behavior of the engine or other electronic components. If you’re experiencing these symptoms along with the P0356 code, it might be pointing towards an ECU problem.

Diagnosing ECU issues can be tricky and often requires professional equipment and expertise. A mechanic can perform a detailed diagnosis, checking for additional fault codes and inspecting the wiring harness for any signs of damage or corrosion. They can also ensure all connections are secure.

If the ECU turns out to be the culprit, a professional can guide you on whether it’s more cost-effective to repair or replace it. Given the complexity of vehicle electronics, getting a professional opinion is often the best course of action.

Hope this helps and best of luck with your car troubles!