CEL turned off?

Here’s the story. I have an 07 Saturn Ion with 107k miles. I took it in for an oil change on Wednesday. Immediately after the oil change, the check engine light came on. On my way home i took it to AutoZone to check the code (i cant remember the exact code) and i was told it was the O2 sensor. The light has been on until today. The car was almost out of gas so i filled the tank. When i started the car the light was off. Could the original cause of the light been a loose gas cap or could it still be the O2 sensor? Should i still take it to the shop on Tuesday as scheduled to repair the O2 sensor? Id hate to shell out the $ on a repair that isnt needed.

Drive it. If the light comes back on…have the codes read again and pony up for the repairs.

The problem could also be a weak fuel pump.
Combined with a nearly empty tank, low fuel pressure could have upset the air/fuel ratio and trigger the error code.
A drive cycle or two without the problem and the computer deletes the code and shuts off the light.

Maybe an O2 sensor is not the problem at all. There are numerous codes for O2 sensors and it could be that you’re misconstruing what AutoZone told you.

Providing a code and providing a diagnosis are 2 entirely separate things.
AutoZone’s job is the former.

If the light stays off - just drive on. Sometimes a CEL will turn itself off. Every time you start the car the main computer performs a “check” of all sensors and systems. After several start cycles with all Senors and systems reporting OK the CEL may turn off, the error code remains stored in memory.


Here’s an interesting story . . . and it directly relates to your own

I was changing the oil on my car. While removing the filter, I spilled some oil on one of the oxygen sensors

Later that evening, while I was driving around, the check engine light came on. I checked, and sure enough, the code was for the sensor which had gotten hit by the oil.

When I was back home, I took out the sensor and carefully cleaned it off. I put it back, hooked up my scanner and cleared the code. I got the engine up to operating temperature, verified the sensor was working correctly. Later on, I checked, and the oxygen sensor monitor had run to completion

That was a few years ago, and the fault code has never reoccurred. I know that, because I occasionally check

Maybe something similar happened with your car

I posted a few days ago about my cel light turning on and off.
The light came on again so I went to Autozone to have the code read. It was P0171 bank 1 too lean. I did a little research and found a lot off info telling me to check all of the air tubes, gaskets and even the gas cap. I popped open my hood and immediately noticed the air intake tube was just barely sitting on top of the throttle body. I reattached the tube, tightening the gasket back down. The cel light went off and hasn’t come back on.
Glad I researched the problem!! It seems like the person who did the oil change was maybe trying to check the air filter and ended up pulling the whole tube off. I’m irritated that they did not tighten it back on or at the very least own up to the mistake and tell me so that i could fix it.


That P0171 code . . . is it the same code you had the other day?

The reason I’m asking is because a P0171 means lean bank 1. No more, no less

Those autozone guys sometimes aren’t too bright . . . I could easily see that one of those guys might think a P0171 means the oxygen sensor is bad

When having Autozone read your codes, the best approach is to have them read the codes and write them down for you. do not ask for their advice. Because if an autozone guy got a p0171 code and told you the oxygen sensor is bad, that is just bad advice

In any case, congratulations on seeing the problem and fixing it!

Yes, it was the same code for the first check. The first guy suggested the O2 sensor. The second guy was confused and told me to take in to a shop to have it checked out.

Let me explain lean bank. And, if someone spots an error in my explanation I will also learn something.

There are many sensors in the OBDII systems. One of them is an air flow sensor on the air intake, sometimes by the air filter assembly, I think.

The computer notices the quantity of air which goes by the air flow sensor (probably not what it is called but what it does.)

The engine computer adjusts the amount of fuel injected into the system up and down until the oxygen sensor at the output of the motor says the result is as good as can be.

But, it already knew how much fuel SHOULD have been injected based on the amount of air coming by the sensor.

If there is a disagreement, it will throw a lean bank error to let you know there is a problem.

I don’t have a lot of experience like many of our great mechanics, but when I see a lean bank message, I expect to see something wrong which lets air come into the intake but not via the normal path.

Which is what you had. So, in this case, my simplistic theory agrees with what happened. I THINK/HOPE.

Thanks for letting us know your fix. Glad it was easy and free.


Thanks for the additional information

No doubt about it . . . the first Autozone guy who saw that P0171 code and told you the oxygen sensor is bad is a moron, as far as diagnosis goes

he should not be giving any kind of automotive advice

The second guy, at least he was smart enough to realize he was in over his head. At least he was honest enough to say you may need a proper diagnosis

Playing Devil’s Advocate I might pose the following.
The AutoZone (or whomever) guy finds an O2 code for starters and this evolves into the exact words used to the customer and how they’re being used.

Does the AZ guy state that the car needs an O2 no ifs, ands, or buts about it?

Or does the AZ guy state nothing more than the code is for an O2 sensor and the customer then assumes the AZ guy is providing a diagnosis by providing that O2 code.

I’ve been privy a few times to overhearing a conversation between an AZ (or whomever) employee and the customer with the customer sometimes demanding to know if the part involved in the code is going to fix the problem and the parts store employee repeatedly telling them that they’re only providing a code; not a diagnosis.

In one particular case an older guy was going on for 10 minutes over a MAF sensor code and was even being a bit rude to the employee by constantly demanding to know if a new MAF was going to fix the problem. The employee kept telling him that he did not know and that providing that MAF code was the only thing he could do with diagnosis being on the truck owner or an auto repair shop.
When I left the older guy was still at it…

Not saying that is the case here at all but no doubt it happens a lot.


I hear what you’re saying

But the fault code readout for P0171 doesn’t mention the oxygen sensor at any time

This is the case of somebody jumping to an incorrect conclusion, based on lack of knowledge

I could understand how somebody might interpret P0101 to mean you need a MAF. After all, the MAF is mentioned in the fault code description

FYI, the procedure for reading codes at AutoZone is for the employee to take a code reader out to the car and retrieve the code or codes, then enter the codes into their computer at the parts counter. The computer provides a screen shot of the code, what it tests and possible solutions. They can print this out on their cash register printer.

The printout will have the code at the top and the information below. I’m not sure how the AutoZone clerk came up with an O2 sensor for this as it would be the last thing or near the last thing on the possible solutions. It could be that he knew that the only part they had on hand from the list of solutions was the O2 sensor.

Irlandes gave a good description of this code.