Service Engine soon light came on my Nissan Sentra 2011

So recently my service engine light came on suddenly and I saw my tachometer acting a little weird along with my car vibrating slightly at stop lights. I know I should get this checked out because it’s better to nip this problem in the bud early on before the problem worsens or starts to affect other parts of the car. My questions are,

  1. Does anyone have any idea what the problem is? I’ve read online that sometimes the service engine soon light comes on because of small issues that can be resolved by e.g. tightening the gas cap etc etc or it may be something that requires professional attention. I don’t want to have to see a mechanic if the issue can be resolved by myself.

  2. I’ve had terrible experiences with mechanics, what often happens is that I get charged for work done and the problem isn’t solved. This happened once with an individual mechanic and I’ll probably look at certified dealers such as Mossy Nissan. But that being said, the reviews of all the Nissan certified service centres in my area have horrible ratings and reviews so even going to them is a hesitation for me.

  3. How can I protect myself from getting ripped off? What information should I ask for or tell them? Do i ask them for the codes when they run a diagnostic test and what should I expect to get charged for and what should I expect not to get charged for.

It’s been hard dealing with mechanics especially since I’m younger and thus, inexperienced. Any help would be appreciated

A loose gas cap can cause the Check engine light to come on.

But when there’s a change in the way the engine runs along with the Check Engine light it’s best to get it looked at as soon as possible.

Until the codes are read which is causing the Check Engine light, there’s no tellin’ what’s goin’ on.


Getting the codes read is the first step. Depending on where you live, many auto parts stores and even Jiffy Lubes will read the codes for free. If you can get the code read, we can help further.

The only thing I will add is that you need to be a bit wary of online reviews as the actual stats can be skewed because of a relatively few complaints.
Most people will complain loudly but will not offer any praise at the same volume.

Ask your friends, family, or neighbors for a recommendation. I’ve been using a mechanic for 20 years based on a neighbor’s recommendation. This year, my wife’s van needed the timing belt changed. I asked around work, got a couple of recommendations, and was satisfied with the work done.

Ed B.

Check mechanic files at the top of the page for a mechanic in your area. You need to get the codes read before we can really help. Autozone and Advance will do it free.

“Most people will complain loudly but will not offer any praise at the same volume.”

It’s like throwing away a whole bag of apples because just one is rotten. I agree with @ok4450 completely. Find a good independent mechanic and stay with them.

Please verify if service engine or check engine light on

Thanks for the comments guys, I guess as of now I’ll be getting the codes and will put it on here. It’s the service engine soon light, not the check engine light.

A Check Engine or Service Engine Soon light means the same thing.


So I got my car diagnosed and the code was P0303 which I believe is for the cylinder misfiring?

Should I be worried about this problem and what would be the range of the price of repairs I should expect to pay? I know this depends on what is causing the problems.

What is the worst case to best case scenario?

It could be as simple as a bad spark plug, plug wire, coil, or a faulty injector.

Or worse case you could have a hole in a piston, a burnt valve, or broken ring.

Find a good independent mechanic and they should be able to diagnose this.


You could take it to the Nissan dealership and ask for a diagnosis (~$100). A misfire might come under the extended emissions warranty.

This car was bought second hand, and it has about 40k mileage in it which I was told by the mechanic was pretty unusual for the car to have problems at 40k. Would I still have the warranty covered even if it was second hand?

I think you’re out of luck on the warranty due to time and mileage limits unless there’s a problem with the ECM and that’s unlikely. The ECM, or computer, along with the converter has a much longer warranty coverage.

The code is for a Number 3 cylinder misfire and that could be a spark plug, coil, etc.

I’m pretty sure your car has the 2.0 and a mechanical lifter valve train. Solid lifters require periodic inspections and adjustments and that’s not a warranty procedure either.

With the spark plugs out I would run a compression test and verify that this problem is not being caused by a tight valve. That can be serious or not; all depending upon various factors.

Worse to best

Burned valve or blown head gasket

Spark Plug and coil pack bad

Coil pack bad

Spark plug bad.

Bad coil, plug, injector or leak. Most misfires are fairly straight forward. Don’t know a cost, sorry.

Yes, your # 3 cylinder is misfiring…Most likely cause, failed spark plug, spark-plug wire or ignition coil depending on what type of ignition system you have…A more unlikely reason, a plugged fuel injector…A skilled mechanic can sort it out in a few minutes…

How many miles on the car? Has it ever had its spark-plugs replaced? Driving it like this is not good as it could damage the catalytic converter because of the unburned fuel going in…

It’s easy. Get it diagnosed. That’s all I have.

So quick update, seems like my coils need replacement, at least 2 of them. That along with spark plugs. Thing is, replacing all 4 coils is going to be costly but my mechanic tells me if I change 2 of them it would be better to change all 4 of them, something along the lines of since I’m paying for labor etc". Is that necessary?