Here is an example of a post we see on Facebook in one of the many 10th Gen Civic Groups about once a week. It’s generally accompanied with an image of the MIL (malfunction indicator lamp). 

“Just got this light on my dash, anyone else got this on their car, what's wrong?”

And that’s it. That is all the info presented. A question like this results in more questions than answers. It is then up to the plethora of Facebook master mechanics to reply back with a solution to make the light disappear.

We have customers across the spectrum. From, “This is the first Honda I have owned and I have never turned a wrench before”, to “I’m a 20+ year Honda Master Tech”. Regardless of your experience level, finding the solution takes the same approach. In this blog, we are going to break down 5 simple steps to follow whenever you are presented with a Check Engine light on your Honda Civic and the like as well as answer some common questions. 

5 Steps to Understand a Check Engine Light

1. Read the code(s)

2. Review your last change/modification

3. Check the obvious (easiest thing first)

4. Know the car

5. Ask an experienced tech/mechanic

1) Read the codes

The first one seems obvious but a lot of people don’t know how to do it or simply skip it. Your late model Honda and Acura are very smart. They have dozens of computers and sensors onboard that all talk to each other hundreds of times a second and know when something is out of whack. OBDII equipped cars like the Civic SI and Type R have some standardized codes to help diagnose the problem and a standard plug and way to read these codes. You can plug in an OBD-II scanner under the left side of your steering wheel. Some auto parts stores will pull your code(s) for you for free. Also, Hondata and KTuner ECUs have the ability to pull those codes as well. When you read the code you get a great starting point. Here is an example. P1115 is a fault from the engine coolant temperature sensor. While the code alone does not tell you whether or not the sensor is the issue it does narrow things down quite a lot.

2) What change/modification did you do last?

Let’s face it, we are enthusiasts and we like to modify. Sometimes when we modify we might forget to perform an important step when putting our car back together or we forget we need a re-tune to run the car correctly. It’s not uncommon to see CEL right after a new mod. So step 2 is to go back and check your work. 

Did you pull a MAF sensor fault like P0102  after just installing a new Cold air intake? Chances are you forgot to plug the sensor back in. Car not running right after installing our new 4 bar MAP sensors with a P1129 code?  Maybe you skipped the part about reflashing your car with 4 BAR support enabled. Retrace your steps carefully and thoroughly and odds are you’ll find your mistake.

3) Check the obvious (easiest thing first)

Perhaps you have not worked on the car in months and it’s been running flawlessly up until now. Step 3 is to look for obvious problems. After you have read the code in step 1, you will know where to start looking. Lots of the codes that exist are for sensor faults. So if you got a P1162 sensor fault (air/fuel ratio sensor) for example, look there first. The air/fuel sensor on the turbo 10th gen Civic is right on the turbocharger. Pop the hood and take a look at it. Look for the obvious. Is it unplugged? Are the wires cut or chewed through. Sometimes the simple things to check are all that’s needed and can save you dozens of hours under the car and on the internet trying to chase down a 5-minute fix. 

4) Know the car

Step 4 applies to you👈 specifically as a performance enthusiast. Your car is not stock. You have bought dozens of 27WON and other aftermarket goodies and have modified the heck out of your ride so it's important you know what you have done to it. It’s possible there is a very specific piece of information that pertains to your car and your problem that is the link needed to help figure out the problem. 

I’ll give you an example. You are trying to diagnose a charging system error on your AccordX. You keep getting a fault P16BB code and think the alternator is going bad. Maybe you have even already replaced it once or twice. However, you forgot that your father-in-law did a (subpar) subwoofer install and cut into some important power and ground wires. You are trying to diagnose a charging issue when it’s a bad wire the whole time. 

5) Ask an experienced tech/mechanic

Rounding out with step #5, ask a qualified mechanic or shop to help you diagnose your problem. As easy (and free) as it is to ask a bunch of car guys on Facebook, the answers are often not very reliable. This is not a knock on people trying to help, it’s just that your question will quickly turn into a conversation about how slow all the other cars out there are :)

So next time that little lamp turns on, reference this blog and I assure you that you will get back to enjoying your car sooner.

Here are a few common questions and answers about Check Engine Lights.

1. What does the check engine light mean?

   If the CEL is on it means that an OBD II monitor has detected a fault in your car. Basically, something is out of spec and the car is alerting you to let you know its not running optimally or within emission compliant range.

2. How do you reset the check engine light?

   You should only ever reset a check engine light if you are confident the fix has been implemented. You can reset the light with a Hondata or KTuner device or with most standard OBD-II code scanners. 

3. What are the most common check engine lights?

   There is not really a common check engine light as there are hundreds of possible scenarios. But as a CivicX tuner, you can expect to see a P0420 for catalyst efficiency or a P0128 for coolant thermostat temperature check. Both of these generally come from modifications we have made to our cars. 

4. Is it safe to drive with a CEL on?

   Depends on the severity of the code. If the CEL is not flashing, you are generally fine and can get around for a bit until you can fix the issue. If the CEL is flashing while you are driving then you should get home and park it until you get the chance to figure out what is going on. 

Share any specific thoughts you have on this subject in the comments below. We’ll edit this blog to share the knowledge from the community and make it more helpful to our readers.  

REDEFINE the Aftermarket

-Vincent