Many or most of us will at one time or another experience problems with our automobiles that will be indicated by the check engine light coming on.
I recently talked with a well-known mechanic about this problem.
I have done nearly all of my mechanical work for many years so I was quite interested in what he had to say. I admit that I have done less since the automobiles have become more complex.
The important thing that he told me and I assume it is correct is how the check engine light actually works. I read in many forums and hear from people how they go to Auto Zone or some parts place and get a free check to see what is causing the check engine light to come on. Most of these parts stores perform this check for free. It is a wonderful service to the customer.
With that said, I must explain how my mechanic friend explained about the check engine light, and what is really happening.
I will attempt to explain this in laymen’s terms.
My example is that the check engine light comes on. The tester is put on the car and it discovers some problem. It is quite common that it is the 02 sensor located on the exhaust side of the engine.
People will often run right out and get a new 02 sensor. It might or might not fix the problem.
The reason it might or might not fix the problem is that this sensor is monitoring the quality of the exhaust gases to make sure the engine is burning the gasoline efficiently. If this gasoline isn’t being burned efficiently, the 02 sensor will detect this and the check engine light comes on.
Most auto parts stores will sell you the bad sensor. This is where there can be a very real problem. It might or might not work. The reason being that the check engine light came on, because something in the engine isn’t working efficiently. Therefore, very often the light might or might not stay off for a while but will come back on. This can be in minutes or hours, days, etc.
The thing I have run into on more than one vehicle is that I didn’t need the sensor that I was told was defective. I needed new spark plugs. Once the spark plugs were installed, the check engine light stayed out.
This simply means that the sensor is working properly and detected a problem in the engine. It doesn’t mean that the sensor is defective. Something triggered the sensor. This could be poor air/fuel mix or a weak ignition system. It means that there is more than likely a problem with the engine, and it really has nothing to do with the actual sensor.
It also means one shouldn’t just replace expensive sensors without knowing what is actually going on with the engine. It also means that the engine should be checked, and not just the computer and sensors.
I found this interesting as so many times people say, they had to replace this or that sensor, only to find that the light comes back on.
I recommend finding a reputable mechanic before replacing a “bad” sensor so that the money can be put where it belongs which is to repair the engine, not just replace the sensor.
I welcome other opinions.
To somewhat substantiate what I posted above. I installed new spark plugs in my 2004 Tacoma. I ran the truck for a total of about 15 minutes, shut the truck off, came back 30 minutes later, started the truck and the “check engine” light is off.
Indicating that it was poor emissions produced by poorly firing spark plugs. The sensor detected the poorly burned gasses, set off the light, but once the engine was burning the gasses correctly, the light went off.
6 spark plugs costs way less than a new sensor, especially when the end result would be new spark plugs anyway.
Just replacing items via guess work is not a way to go about it. If you needed new spark plugs then you should have gotten them anyways
There is an error code that accompanies the check engine lite. This tells you where the problem is located.
My truck you need to turn the ignition to accessory then off 3 times then the error code shows up.
Then you can determine what to fix.
Few examples: Something as simple as a leak in the emission system can cause an error code, a loose gas cap. Then you wasted $$ on replacing a sensor. 80′s model toyotas were this way, newer model have a computer than generates an error code.
Lets say me error code is a P0171 for a 2004 toyota tundra.
Search google for “2004 Tacoma error code P0171″, then you will get some results of what people did and how they fixed it.
Hope that helps
I know just about that much about the new cars and trucks. With the truck it was time for spark plugs anyway.
I also have a car that is sending error codes. They have basically been covered. I searched on how to reset the ecm but haven’t had a chance yet.
Probably end up taking it to a dealer.
Actually went to a tech school years ago, but with all the changes it might just as well have been for Model A’s.