Trouble Codes C1201 and P0303, check Engine and VSC lights on?

Hi,

If there is an issue within the engine control system, the computer turns off the vehicle stability control (VSC).

Since you have a P0303, that tells me there was a misfire on cylinder three of the vehicle. Did you notice a misfire at any point? When was the last time spark plugs were replaced?

If you clear the two codes with your scanner, do they come right back? Try this if you haven't. I suggest it because the options are very limited. Take a look at the pic below.

I have a feeling because of the misfire (P0303) the C1201 was set. If the vehicle is running properly, clear the codes and see if they return. If the spark plugs haven't been replaced for a long time, you may want to consider a tune-up.

Let me know your thoughts and what I can do to help.

Take care,

Joe

See pic below.

I don’t know when the spark plugs were replaced last. I cleared the codes, but they came back 3 days later. I haven’t noticed a misfire or other obvious performance issues with the car. Is the #3 cylinder easily accessible on this vehicle? If so, I can at least replace the plugs that I can get to myself.

Hi,

I would be happy to tell you where it is, but you won't be happy. It is the center cylinder closest to the firewall. Did the P0303 return as well? If it did and you plan to replace the spark plug, I strongly recommend replacing the coil pack at the same time, so you don't have to do it twice. The OEM part number for the coil is 9091902246. You can get an aftermarket one for less money, but I don't recommend getting an inexpensive one online. I have seen so many issues with online parts lately.

See pic below. Note, the arrow in the picture points to the front of the vehicle.

Let me know.

Joe

See pic below.

Crap. Had to be at the back of the engine. What should I expect to pay for a tune up? Do you think - based on what I told you - that its the plug and not the ring or valve?

Hi,

Not knowing where you are located, I don't know what the charge would be. I wouldn't think you should be charged more than an hour of labor.

As far as rings or a valve, chances are if the vehicle was maintained, that isn't an issue, but it is possible. To determine if it is a compression issue caused by one of the things you mentioned would require a compression test.

Here is a link showing how it's done, but you would still need to remove the spark plugs:

https://www.2carpros.com/articles/how-to-test-engine-compression

If I had the vehicle at work, the first thing I would do is remove the spark plug to see what it looks like. At the same time, I would switch that coil pack with one easy to access to see if the misfire changes cylinder. If it would, it would be easy to access the coil to replace it.

Let me know your thoughts and if there is anything I can do to help you.

Take care,

Joe

New clue. I don’t know if this helps, but I cleared the code and drove the car for a day and a half with no problem. Then I rapidly accelerated, and the lights went back on. No change in feeling from the car or engine. No sounds. Just light popped on when the car went into overdrive. Does that help in diagnosing the issue?

Hi,

Did the same codes return? If they did, then I would likely try replacing the coil and spark plug in cylinder 3. If the misfire has changed the cylinders, then we may have an issue with the controller.

let me know.

Joe

Same codes. Same cylinder. What about flooring the engine would provoke the codes to reappear?

When the vehicle is under a heavy load, it requires more fuel and air. If we have a bad plug or coil, it may not burn the fuel properly causing a misfire.

Let me know.

Joe

Since I don't know when the car last received a tune up, I just ordered all new Denso coils and new Denso Iridium plugs. I figured if I am going to do it, I might as well do it right.

Hi,

That certainly is the way to do it. LOL If you need help, let me know. Also, let me know how things turn out for you.

Take care,

Joe