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Check engine light

My check engine light went on and I want to get it checked. I was told some places check it for free but when I googled it it came up with something about check engine light scams. Does anyone have any advice or know about these “scams” they are talking about?

Call some chain auto-parts stores to see which ones can do it. When they give you the results, write down any or all of the five character OBD2 codes and then post them for help here. Do not just buy the parts that the auto store claims the codes mean to replace.

Some people (who don’t know any better) might call the whole “check engine light” thing a scam - some think its a big government joke. Others think its a big scam on the part of car dealers to get you into the shop for no good reason.

Others (who also don’t know any better) might think that auto parts stores reading codes for free is scam-like b/c they just use it as a way to see unneeded stuff. This does happen, but only b/c people don’t know any better.

So just do as tardis said and find and auto parts store that reads codes. Don’t listen to them (within bounds of being polite) and don’t buy anything. Just write down the codes - they look like “P1234.” Then post the codes here.

Most big-chain auto parts stores will do this (Advance, Autozone, Checkers etc.)

Hello and thank you and everyone else for helping. I got the car checked out and have some codes. The codes are D0125 and that involved the air fuel sensor ratio and the other code is P1135 which was something to do with a heater circuit malfunction. It was suggested that I replace the air fuel sensor. I asked about the other issue of the heater circuit and they said that if I replace the air fuel sensor that would fix the heater circuit malfunction code to. I am wondering now if that is why my car has been smelling really gassy/fumey when I am driving it…almost like the fumes are getting inside. Anyways I appreciate all the help. Thank You!

AFAIK, there is no valid “D0125” code. P0125 has to do with engine coolant temperature, not fuel, so I don’t know what code you really would have there.
P1135 might be fixed by changing an O2 sensor, but it could also be wiring, a fuse, or the PCM. I think that you need to get it properly diagnosed instead of throwing parts at it.

If the code actually is P0125 (rather than D) then you should absolutely check out the coolant temp sensor and the thermostat. In fact, if the thermostat hasn’t been changed in a long while its a good idea to just do it along with a basic cooling system service.

Is your heat working well?

The P0125 means that the coolant temp sensor is not reporting hot enough temps to enter “closed loop” air/fuel control. That means it will leave it in open loop - this is the equivalent of driving around with the choke on which means that the engine will run rich (too much fuel). It might thus smell “gassy/fumey” when running. It may also be the reason for the P1135.

What is weird is the guy who read the code said D like Doll. What would be the code for the air fuel to ratio sensor? I am really confused now I guess I will try calling them back. Oh and yes the heat works totally great. Again thanks for yours and everyones continuing help I really appreciate it.

How do you get it properly diagnosed? I thought that is what I had done when I took it in and spent the $40 for them to do it. I am hoping I didn’t just waste that money. Again thanks for all your help I appreciate it a lot.

“How do you get it properly diagnosed? I thought that is what I had done when I took it in and spent the $40 for them to do it.”

The codes that get pulled out are called “diagnostic trouble codes” (DTCs). They’re called that because they are a starting point for diagnosis - they do not provide the diagnosis.

So, I’m going to assume that your code was actually P0125. All that means is that the computer, after waiting a specified period of time, hasn’t gotten a temperature report from the coolant temp sensor that says the engine is hot enough to go into closed loop fuel management. What it doesn’t tell you is why. Is there a wiring problem between the computer and temp sensor? Is the temp sensor itself bad? Or is the temp sensor just fine and the coolant really isn’t hot enough?

Figuring that out is the diagnosis - computers can’t do it. Since you get plenty of heat I’d have the coolant temp sensor checked.

And I would not bother with the P1135 until that is cleared up. If you have a P0125 that issue will mess with the air/fuel sensor (basically your upstream oxygen sensor).

Thanks for all the info just want to ask one more thing in regards. Is what they told me I need to replace, the air fuel ratio sensor, would that fix the coolant thing that is wrong with it oh and is it ok to drive like this or is it bad for the car and can lead to more problems. Again thank you!

No, changing the O2 sensor wouldn’t help with the coolant temp problem. Fixing the coolant temp problem might help with the O2 sensor issue.
It’s okay to drive it for a little while, but you need to drive it to a good garage (not a national chain) and have it correctly diagnosed and repaired. You are wasting fuel, and you are probably at least doing damage to your catalytic converter (expensive).
Yes, failure to repair it soon will lead to more and more problems.

So is it just that the diagnostic they gave me was wrong or were they giving it their best guess? I took it to a small reputable place so I am not sure what to make of their diagnostic and advice to replace the air fuel ratio sensor when it is a coolant issue, or what to make of the code that starts with a D when that code doesn’t exist or can’t be found. What type of service is involved in fixing the coolant temp problem and do you have an idea to how much it might be. Sorry for so many questions but just a little confused on how to proceed without wasting money on it might be this or it might be that. I know with cars that is just sometimes how it is unfortunately though. Anyways many thanks.

Ok one last ting the 02 sensor you are talking about is the same as the air fuel ratio sensor? Just curious because when researching other forums I saw in a post someone advising of this possibility … " on some models, Toyota does not adhere to the SAE standard definition for DTC P0125. That code can be for a Coolant Temperature Sensor concern, but it can also relate to O2 sensor function. Just curious.

Let me play devils advocate here for a minute about the chain parts stores. Many people post that the store “said this, that, and the other” after a code, or codes, are shown.

Did the parts store really say that part is bad or is the mechanically lacking customer reading more into it than what the counter guy is stating?
In other words, if the counter guy showed an O2 code present did he really state that an O2 was bad or did he tell the customer the code pointed to an O2 and the customer leaves after “being told the O2 was bad”?

I’ve been in chain stores many times and within earshot of some of the carp (sic) that goes on and if I were a counter guy I’d quit and go dig ditches.
One older gentleman with a very late model Ford pickup went on for 10 minutes straight with the counter guy about “is that MAF sensor REALLY going to fix the problem?” The counter guy kept telling him the code was a MAF code but the guy was insistent and complaining about “well, I ain’t gonna spend XXX dollars on a MAF sensor if you can’t tell me if it’s bad or not”.
The counter guy has much more patience than I do and when I left the guy was still at it.

The A/F ratio sensor is basically an oxygen sensor. They’re a little different, but not enough that you care. When the car runs in “closed loop” the computer is getting its info about the current fuel mix from the A/F ratio sensor. That’s how its deciding how much fuel to fire into the cylinders. This is what your P1135 was about.

If the other code is P0125 it means that the car isn’t getting to closed loop. So you might have an A/F sensor problem. But as long as your car’s having trouble getting to closed loop the function of the A/F sensors is somewhat irrelevant.

I know nothing of Toyota having a screw up with the DTC standards. But anything is possible. What I do know is that it would take me all of about 10 minutes to check out your thermostat and test your coolant temp sensor. Its not hard.

Just pulling the OBDII codes is not a diagnostic.
A diagnostic involves pulling the codes, inspecting the car and engine, and then working the troubleshooting flow charts for each OBDII code as well as checking anything that the inspection revealed.

I called and they did check the thermostat/coolant system and found nothing they could see wrong. My car also is not running hot at all. The mechanic is still saying that even though the code is for engine coolant temperature that he still maintains replacing the air fuel ratio sensor is what should be done. Does that make any sense? Maybe I should just take it in somewhere else for a second opinion and have the thermostat and coolant system. Thanks again.

Hi I am going to get it fixed but don’t know if I can before I have to drive 2 hours away to the airport. How soon would the catalytic converter start getting damaged beyond repair? Also someone said I should just replace the thermostat…would that fix the coolant temp problem? Thanks again.

If the light isn’t flashing at you and the car is running reasonable well then I wouldn’t worry about doing whatever you have to do before getting it fixed.

Replacing the thermostat once in a while is a good idea just as a basic maintenance procedure. Theremostats are cheap and normally very easy to replace (that does vary) any time the cooling system is services. So if you have the cooling system serviced with a new thermostat install you haven’t lost anything regardless.

You still never actually clarified the code that you reported as “D0125”

When I called the shop and told them that there was no D codes but there was a p code they said it must have been a typo and it must be code P0125. Is that sound right? It seems like when you read the codes they come out pretty basic and that they should be able to be read pretty easily. I don’t know. Also whats weird is they gave me P1135 which I am being told if there is a 1 it is based on the manufacturer and I do believe P1135 is for a Mazda not Toyota. The code P0135 is the general code for the same thing. I think they must have meant P0135 and P0125 but it still is a little unsure.