New battery issue

Soooo...

 

This morning my car was running perfectly fine. 100%, not an issue at all. During my lunch break I had my battery changed (72k) on the original at my local Advanced Auto. After finishing up, I noticed the check engine light was on, along with a flashing cruise light. I didn't think too much of it as I know things sometimes need to 'reset' after a battery change...at least they did with my old VW.

 

I drove it to a nearby gas station, maybe half a mile away. It drove fine, no noticeable issues. Turned it off, got gas, normal stuff. When I got back in to turn it on, it didn't want to start. On the 3rd crank it fire up but was running rough. I wasn't expecting this. Drove it to the nearest dealer and let them know the situation.

 

Called them a few hours later and they told me the negative terminal needs to be replaced (corroded) which I wasn't surprised to hear, but what did surprise me was the fact that they weren't able to access the car's ECM. So, needless to say, their keeping it over night now. Awesome!

 

I'm already $288 in the hole and their still not sure what the problem is.

 

Does anyone have any idea what the issue could be? The fact that their not able to access the ECM makes me nervous, like I'm sick to my stomach thinking I'm going to need something expressive. How can changing a battery cause something like this?

 

I had something similar happen recently, and to make a long story short it went away on its own in around 3 days or so I think. I don't know about the ECM part though, I'm not sure if mine was accessible or not.

 

What I think triggered this issue for me was turning the key to the second accessory position, with the MAF sensor unplugged. Threw a few cel's, cleared them out, but the car still wasn't happy. Tried replacing plugs, wires, cleaned maf sensor, reset ecu a few times, still wasn't happy. Started the car up one morning, and everything was 100% perfect again. I remember reading in another thread someone with this issue brought their car to subaru, and a tech said some sensor needed time to reset. No idea what sensor that could be though. I've been through the relearning process many times too as you said, but nothing like this, the car was stalling/stumbling/running rough, didn't want to start, just not running right.

 

**I also just wanted to mention that I've read through a few threads where all kinds of strange issues were simply due to a weak battery, even though the battery was brand new. The battery just needed some driving time to charge up more, or get charged up through an AC battery charger. I guess it makes sense that "new" batteries could discharge from sitting in the store, especially since auto parts stores might not go through batteries as fast in the spring/summer.

Anytime you reset the ECU, either by OBDII or unplug the battery, the ECU needs time to relearn the fuel trims. It could take up to 15 - 20 mins of driving around. You will notice rough idles and hesitation when coming to a stop.

 

The dealer not able to access the ECU is not a good sign. I tried hooking up my OBDII scanner to my buddies Toyota Truck once and the scanner could not read the ECU. Only to find out the ECU was fried. Not sure what happened, but something shorted it out.

I replaced my spark plugs and obviously had the battery out. Afterwards it kept stalling and running/responding to input terribly. I did a idle relearn which from what i can remember was make sure anything that draws electricity like the radio was turned off, take out battery for 30 min, put it back in, put key in on position 15 to 30 seconds, start and let run i think 10 min without turning anything else on or touching gas pedal. Turn off, leave key in, put key in on 15-30 sec, start, let it idle like 5 10 minutes and turn off and it was fine after. No more stalling or slow responding to throttle input

Ok, just got the call. They ended up having to replace the negative terminal, clean the intake man. and replace a fuse.

 

When I get to the dealer, I plan on asking a few more in depth questions just to make sure I have everything straight.

Maybe they cleaned the MAF.

I just remembered something. I also got my replacement battery from advance auto parts, and had a small problem when I got it. Even with the negative battery terminal tightened all the way, it was still possible to take the terminal off the post. I ended up having to take out this small plastic ring and spacer that comes on the negative battery terminal from the factory. Removing that ring allowed me to securely tighten the terminal onto the post.

 

Did you install the battery or did someone from advance do it? Do you remember if the negative terminal seemed loose if you did?

 

Small picture of the ring/spacer in the link below, best I could find.

http://legacygt.com/forums/showpost.php?p=4233697&postcount=373

The negative terminal was severely corroded, and I knew this before hand. The Advanced Auto guy that installed it said the same thing, so I'm not surprised it needed to be replaced. I think that it was so bad that it wasn't able to stay 'tight' after installing a new battery.

 

They said because of carbon buildup they needed to clean the throttle body, they didn't mention anything about cleaning the MAF though.

 

Finally, even after all that, the car was still throwing a CEL. The tech had to call Subaru to get some more details on how to tackle the problem. Apparently, one of the fuse's (the one for the ECI?) was shot and needed to be replaced as well. Once that was done everything was good to go.

 

Anyways, that what I was told.