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CEL on after replacing battery

I have a 2005 Subaru Outback 2.5 XT, and had the battery (which had been very sluggish on starting recently) replaced at Pep Boys yesterday. It started up just fine after the battery was replaced, but the CEL light came on with the cruise light flashing.

The Pep Boys mechanic read the codes: P0102 (MAF Circuit Low Input) and P0113 (Intake Air Temp Circuit High Input). He said that the codes are unrelated to the battery replacement, and that they probably showed up because the computer is re-learning after the battery replacement. I’m planning to bring it to my local garage in the next couple days, but wondering if anyone has any thoughts on this.

Other than the battery issue, the car has been running fine lately, and I didn’t notice any issues on my drive home from Pep Boys.

Did PepBoys use a memory saver, while they were replacing your battery . . . ?

Something just occurred to me . . . the intake air temperature sensor is probably built into the mass airflow sensor. Perhaps the electrical connector isn’t fully seated.

IMO a simple battery replacement should not cause those specific fault codes

Is the battery located under the hood? If so, perhaps it was necessary to move some stuff out of the way to better access it . . .

Thanks for the response.

I’m not sure if they used a memory saver, but I’m guessing they did–the radio presets and everything were unchanged. The battery is under the hood, but in a very easily accessible spot–I doubt they would have had to move anything out of the way to get to it.

I read somewhere else that the mass airflow sensor and the air intake sensor are the same thing on this car, but not sure if that’s actually the case or not.

I was also wondering if the codes would go away as the computer re-learned/re-adjusted following the battery replacement, but I drove it about 25-30 minutes home from Pep Boys, and the codes are still there after turning the car on today. I never got these codes before (it’s been a couple years since the CEL came on, and the codes were totally different then), and don’t really see why they would all of a sudden show up after replacing the battery.

It takes several start/stop cycles for the CEL to reset. Give it a few more days if you think that is the issue.

Your car was in the shop for a battery replacement. The shop performed a complimentary courtesy inspection of your vehicle to inform you of any needed maintenance or repairs. They inspected the air filter, which is difficult to do without unplugging the MAF/IAT sensor. They put the air filter back in but didn’t get the sensor plugged in properly, which will set a fault code immediately on start-up.

Replacing a battery will not turn on the engine light.


I think you’re on to something ASE.

That makes sense. I wish the mechanic at Pep Boys had mentioned that possibility, but I’m just about due for an oil change anyway. I’ll take it to my regular mechanic, and ask them to check to see if the MAF/IAT is plugged in properly.

Thanks again for the thoughts and suggestions.

It’s easy enough to check it yourself. It’s a simple plug that sits on the side of the air filter box. Very easy to get to. Hope that works.

…and now you know why we always advise people that the better mechanics are not likely to be found at places like Pep Boys.

My boss recently conducted interviews, for prospective mechanics who wish to work for our fleet

One of the guys worked at Pep Boys, and he was not hired, when it became clear his diagnostic skills were “lacking”

Apparently, this guy had been talking himself up during the oral interview

And when it came time for the hands-on part of the interview, he didn’t know which end was up :confused:

Bottom line . . . he was just full of hot air :balloon:

And this is what he got :round_pushpin:

You’ll have to hover your cursor over the last 2 emojis, to see exactly what they are :smirk:

I have no doubt there ARE good mechanics who are currently working for, or have previously worked for, Pep Boys, but this guy wasn’t one of them

I went out and checked it, and sure enough the MAF was completely unplugged. I didn’t start the car up, but I’d be very surprised if that didn’t solve it. Thanks everyone for the help!


…and the best part of this scenario is that you have learned that you should NEVER return to Pep Boys for anything requiring mechanical expertise.


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Pep Boys is a place where young mechanics get experience before moving on to a better paying position.


after you re-plugged, code will still be in place, so you would likely have to “clear” it

unplugging negative lead on the battery for 20-30 minutes will do

you lost your self-learned ECM data anyway, it will make it to start compiling it again, which is a good thing given you drove with no MAF :slight_smile:

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Actually, assuming there are no other problems, that light should eventually turn off by itself

Might take awhile, though

Also a place were non- trained old ‘mechanics’ go to die. About 2 decades ago 60 minutes? did an expose’e (spl) on this very thing. I am commenting from memory so accuracy is questionable. They unplugged an electrical connection (left in plain sight) on a Ford Taurus which caused it to run very badly and took it to chain auto repair places like Sears, Firestone, and Goodyear. It was ‘Repaired’ unsuccessfully at much expense. A couple tune-ups (spark plugs and wires), and a fuel injectors replacement. Between the second and third ‘repairs’ they stopped for fuel where the teenage attendant informed them their car was running very rough. He disclosed he was not a mechanic but offered to look under the hood. Of course he immediately discovered the unconnected electrical connection and plugged it in. The car of course ran normally. When asked what the cost was for the ‘repair’ the attendant answered “nothing”. “I just plugged something together”. I think they tipped him 20 or more dollars. They then unplugged the connection and went to the third chain ‘repair’ place which replaced the fuel injectors. Please people! Never! Never! Never! Allow these pretend repair shops to check the air pressure in your tires much less change your oil or do any diagnosis or repairs on your expensive vehicles!


If I ask my mechanic to just clear the code during an oil change, will there be any issue with the self-learned ECM data? I only drove about 10 miles with the MAF unplugged, so I’m guessing the ECM will be able to discount that data given how much else there is.

I definitely will not be going back to Pep Boys or similar places for even basic service, like this. Last time I replaced my battery (on an old car), I did it myself in a few minutes in the Auto Zone parking lot. I saw that Pep Boys did free replacement with the purchase of a battery, and given the lousy weather, that sounded good. I ended up waiting 2 1/2 hours for the replacement, so even without the unplugged MAF, I was not very impressed.


A word of caution . . .

If you’re contemplating doing your own battery replacements again, you might want to consider a memory saver

Not only will it preserve your radio and clock settings, it will also preserve your readiness monitors . . . an important detail, if the car will be due for smog inspection soon. It would suck to show up at the smog inspection place, only to get turned away, because the car’s not ready. That’s time wasted, in which you could be be doing better things

There are a few cars out there, that require a radio code, if the battery was disconnected. This is typically written down on a card, that you get when you buy the car. I write mine down in the owner’s manual, because I’m less likely to lose that, versus a small card. Anyways, if you can’t remember the number, or lose the code, the dealer will often happily charge you money to get your radio going again, when you show up on their service drive. Maybe they’ll do it for free, if you’ve been a “good customer” . . . in other words, if you spent a grip of cash there often and/or recently

Check out amazon . . . they have quite a few different versions, most are moderately priced, IMO

I usually replace my battery myself, but when my battery needed to be replaced a couple of years ago, I opted to have Auto Zone install it for me–gratis–because my creaky old back was acting-up that day.
The assistant manager did the installation immediately, and my entire visit…deciding on which battery…paying for it…having him gather his tools…transporting the battery & tools to the parking lot…and installing the battery took ~25 minutes, in total. Of course, I gave the guy a tip.

I’m sure that the absence of other customers was a major factor in the speed of service, but I was very pleased with how fast I was able to get out of there with my new battery in place.

knowing pepboys they probably left it unplugged on purpose hoping you would bring the car back and they could screw you by just plugging the MAF back in and charging you for a bunch bogus repairs that weren`t done.

yes, they are that dishonest at least the pepboys store around here is.or maybe they arent dishonest maybe they are just completely incompetent.

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