I beg to differ. You attach the code reader, read the code, look it up in the book and it will tell you exactly what it is. A check engine light is usually the oxygen sensor. When my friends and I do this, it takes 5 minutes to make the diagnosis.
The fact of the matter is they guy asked on a message board what it is likely to be. I’ve told him what it is likely to be. I’ve never charged anything for this and in my experience, the book is always right on what the code is. An oxygen sensor is easy to change if you have an oxygen sensor socket, which is extra deep with a groove on the side to allow the cables to fit.
But all the ones that have repair shops attached are so licensed. You can tell the difference if you are a driver with legally sufficient eyesight to drive by looking for the large repair bays with roll up doors next to the parts show rooms. The Pep Boys (Manny, Moe and Jack) is just such a one in California with both parts and service.
When you say something that is so wrong, it just makes you look stupid Rick.
Like I mentioned above, if you’ve got a smartphone or tablet getting a scan tool so you can just pull the codes yourself (and then post them here) would probably be a good investment and way cheaper than taking it in for an intermittent CEL. The only sort of rub is that it looks like Apple products don’t work with the super-cheap bluetooth ones, but there are slightly pricier WiFi ones out there that apparently do work.
And yeah, The Second Stone, you’re just plain wrong. There was a time in the very earliest days of computerized engine controls that the O2 sensor was at the top of a short list of things that could go wrong, but those days are long since gone. The gas cap is a good guess because it’s easy to accidentally cause and easy to fix, but beyond that there’s really no easy guesses with a CEL issue these days.
The point is that there’s just so many possibilities that it’s pointless to start trying to fix a CEL problem without finding out why the light is on by checking the codes. The one exception is checking that the gas cap isn’t loose since that takes about two seconds, but I wouldn’t do anything whatsoever beyond that before getting the codes.
As Rick pointed out, the fact the code says “O2 sensor bad” does NOT mean the issue is *always * and *only * a defective O2 sensor.
It may be something upstream. It may be something upstream which trashed the O2 sensor and replacing the now-defective O2 sensor will give temporary relief until the existing upstream problem trashes the new sensor too. Or it may be something which has nothing to do with the O2 sensor itself but which causes a non-defective O2 sensor to output garbage readings which the OBD detects & reports as “O2 sensor bad”.
Yes, in some, perhaps many, instances the “O2 sensor bad” code means merely that the sensor failed on its own. For homebrew mechanics who are content to keep replacing stuff piecemeal until the problem stops recurring, replacing O2 sensors with no additional troubleshooting may be an adequate technique.
For pro’s who’re expected to get all the problem(s) resolved the first time, that’s not a good technique. Better to troubleshoot upstream and related systems to understand the complete picture. *Then *start buying & replacing parts.
The “Check Engine Light” also sometimes called “Service Engine Soon” is really a misnomer. Your engine does not really need to be serviced soon, nor does your engine need to be checked.
The various sensors that will set the CEL are mostly emissions control related and do not indicate an emergency situation. The exception is a flashing engine light that indicates multiple misfire and you really need to look into that right away. You will usually also notice drivability problems when this occurs.
The sensors go through several cycles determined by the programing in the PCM (power control module or computer), if the fault happens a certain number of times then the CEL is lit. If the sensors go through another number of cycles without detecting a fault then the PCM will often turn the light back off.
If your light comes on and there do not appear to be any other issues with the drivability of the car, don’t panic, it is probably nothing serious.
Code readers are fine, if you have some moderate mechanical skills, if you don’t they are not going to be real useful. The code descriptions are a bit obscure and only point you to an area that might be the source of a problem.
Even the common loose gas cap code will not tell you that you need to check the gas cap. It will say something like “EVAP leak detected” or something like that, which is not going to help most people.
Look at it this way, there is no direct connection from the ignition switch and the check engine light. (yeah I know the ignition switch turns the system on, but it won’t create a check engine light.)
Also GM shops are organized by specialty. The guy that does ignition switches doesn’t do check engine lights, so there would be zero incentive for him to mess with your car. Also as I mentioned before, it is damn hard to create a problem that won’t show up right away.
Coincidence is NOT causation.
Remember that thing I said you were doing to make yourself look stupid. Um, yeah, you’re doing it again.
You have the same attitude that everyone had when OBD first came out. That attitude lasted in my shop all of two weeks. then Bob got a car with a code for an bad ECT (Engine coolant temp sensor) He had the code so he replaced the sensor. Light came right back on. Stupid parts department must have given him a bad sensor. Installed another one. Light came back on. We now have three brand new sensors all show as bad.
Boss gives me the car. It took a bit of hunting, but the terminal for the coolant temp sensor had backed out of the ECM harness connector.
Just off the top of my head here are a few of the actual causes of MILs with O2 sensor codes:
[ul]
[li]bad mass air flow sensor[/li][li]rat chewed the harness[/li][li]harness rubbed raw due to bad routing[/li][li]leaking fuel pressure regulator[/li][li]bad thermostat[/li][li]bad ECT[/li][li]leaking fuel injector[/li][li]bad rear sensor causing a front sensor code[/li][li]poisoned sensor caused by wrong sealant used in engine (while this is a bad sensor, if you don’t fix the root cause, you will replace two or three sensors before the sealant stops killing them)[/li][li]Contaminated harness (this car got 7 new sensors before I was given the car)[/li][/ul]
The most common time we replace O2 Sensors is when there is no code and we have a smog failure. When we scope the sensor it is working, but the cross counts are very slow. Replacing the sensor under this scenario fixes it
You don’t give up easy do you?
You know when you are in a hole you really should stop digging.
Where I come from most is more than half, you know 50% +1. Looking at the Pep Boys shop locator they have 8 stores with service centers within 10 miles of me. On the other hand O’Rilley’s ( a National chain that does not have service centers) has 25 parts stores within 10 miles of me.
I stand by my comment and unless you have a good cite to contradict me, once again you are wrong, but thanks for playing.
Seriously aren’t you getting a bit tired of always being wrong?
yes it always not lupus.
Your earlier post on evap and adding gas was on topic and well thought out.
Yeah, so as I type this I’m sitting at home waiting to return to the dealership after a slew of (apparently needed) repairs to my vehicle.
As expected, I’m looking at quite an expensive fiasco here (almost $500) but really, given that I’m not a gearhead a lot of what the technician described to me went way over my head. I’m going to look over the invoice when I get back and describe it to you guys; hopefully somebody more knowledgeable than me can chime in to say whether these repairs were as necessary/cost effective as the dealership made them out to be.
One thing that pissed me off: I bought an extended warranty for the car a few years ago just before I hit the mileage cap on the factory warranty. APPARENTLY, the warranty expired at 50K miles - my car is BARELY over that at 50.1k miles - so nothing is covered anymore. I say “apparently” because this same dealership - where I bought the warranty in the first place - had no record of that sale so there was a protracted back & forth before finding out that the thing was expired anyway. Horse shit.
I should get a discount just for that bare lack of professionalism.
