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Mystery Problem; Have Replaced Alternator, Upstream O2 Sensor, and Battery

In the beginning of the year, my 2007 Ford Fusion was in the shop. My grandpa lent me his 2005 PT Cruiser Turbo convertible that only had 20,000 miles on it. Shocking, I know. He hardly ever drove it except on weekends to the golf course.
Any ways, I would drive it to school and the check engine light came on one night when I was running to the drug store. I just left my house and am turning left out of an intersection when my car stalls. Thankfully I am able to get it to go. (I have an automatic transmission)
This started happening often, even when driving on the highway, which was very scary. The radio would even turn off!
My grandpa was able to come take a look at it on the day where I was lucky enough to pull into a parking spot before the car just finally died. I had taken the car to a shop where they said it was the upstream oxygen sensor. I had them replace that. So my grandpa took the battery out of the car and we took it to an o’reillys (where we bought it) to have it tested. As its getting charged, my grandpa and I leave to grab dinner. We get a call that the battery just started leaking acid while it was charging! thankfully, it was just inside of its warranty. Yay! New battery! At least I can drive it to a different shop.
Well, they are having the darnedest time trying to figure out what’s going on. They first said the alternator. Then it wasn’t. It was the O2 sensor. Then it’s the alternator again. I was going nuts, because each day I’d call to check up on it and nobody knew what was happening. So finally they put in a new alternator and all is good.
Well, I just recently borrowed my grandpas car again after giving my car to my sister. I was leaving a friends house and the check engine light came on. I’m going about 10-15 miles and hour when the car starts jerking. I’m not going when I press the gas, but it seems to go when I let off the gas. I finally make it into a parking spot and turn the car off and back on again. The lights still on, but I’m not having the issue anymore. Sadly, on my way home the battery light comes on! I don’t know what to do with this car! HELP!

Start with the fault codes, take the vehicle to a discount auto parts store and ask them to read the fault codes. You can read them yourself, cycle the ignition from off to run (do not start) 3 times. The third time leave the ignition in the run position and read the data displayed in the odometer display, write it down.

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If the battery light is coming on with the engine running, that is almost always a problem with the battery or alternator or there’s a wire that is shorting out somewhere. None of this would usually involve the O2 sensor. Did they explain why the reason they replaced the O2 sensor or sometimes continue to think the problem is the O2 sensor? B/c the symptom isn’t consistent with a typical O2 sensor problem.

Poster Nevada above is correct, the first step to solving this is the list of OBD II diagnostic codes. Then you’ll have some clues to what is happening. Besides the codes, I’d probably measure the battery voltage both when the engine is turned off, then again when the engine is running. If you have the equipment to do that and know how to do it safely, or can get your shop to do it for you, post the results here.

I remember they had read the codes and it said the oxygen sensor was the problem so they replaced that. Then it was still having the issues and so my grandpa and I got a new battery under warranty. I took it to another place while still having the same problem and the battery wouldn’t charge at all so they replaced the alternator. I currently have it at a Chrysler dealership so let’s hope they can figure it out.
Side note: I dropped it off at lunch yesterday and still haven’t heard what’s wrong.

It wouldn’t surprise me if the car originally needed a battery and alternator. When driven infrequently, the battery can self-discharge. If it gets low a lot, this can lead to premature failure. This also puts a big strain on the alternator having to charge up a significantly discharged battery time and again. The O2 sensor could be a real problem or it may have been a result of the marginal voltage when the battery and/or alternator started failing and the voltage got low. The computer might start doing a number of weird things if voltage starved. That may have been a red herring. Anyway, if the battery and alternator now check out OK, the next area to look is the wiring and connections to both to ensure that they are clean and tight. Again, low usage can lead to oxidation of the connections and high charging currents can cause marginal connections to fail over time…

+1…Especially GROUNDS.

fyi to the OP: O2 sensor codes don’t necessarily imply the O2 sensor isn’t working. It’s just saying there’s something wrong in the mixture adjusting process, making it seemingly impossible for the engine computer to set the correct mixture. O2 sensors are pretty robust, but sometimes fail, and that could be a cause. More likely though there something causing an inaccurate assessment of the airflow into the engine, or the gasoline injection process is not working correctly. So engine or exhaust air leaks, MAF or MAP sensor problems, fuel pressure problem, or injector problems.

Might have been an oxygen sensor heater code . . .

It turns out there was a lot wrong with this car. It’s going to cost $3000 to fix it. It starts with the PCM needing to be replaced. Then the O2 sensor has to be re-replaced. And there are some spark plugs and such.

From the description of how the car is performing it likely needs spark plugs and wires.

What is wrong with the PCM? Was it damaged by the replacement alternator?

From what you describe about the trouble, especially with the comment you made about the radio failing also, there may be a problem within the power distribution. Depending where the fault is at, it could cause all the things you described to happen. The trouble seems to be intermittent and that kind of trouble can be hard to pin down. The trouble could be as simple as a dirty connection but the hard part is finding it. Tapping on suspected trouble spots can help find weak points at times. Temperature changes can make a difference also. Hopefully the shop will find the real trouble without too much of a problem.

I can only upload one image per comment but I’m just SSing the email they sent me.

These are not diagnostic results, this is a common inspection form. There are no findings given for the oxygen sensor and the PCM states to ask your service advisor for information.

Before you decide to repair the steering leak ask to see the leak. You didn’t bring the vehicle in to have leaks repaired, it can’t be that bad if it was unnoticed.

The PCM/battery voltage item might be that the PCM controls the alternator charging design, and if that part fails the alternator doesn’t properly charge the battery. It used to be in times of yore that the alternator decided by itself how to charge the battery. But w/new cars, what with all the electrical gadgets used these days, and other gadgets drawing power from the engine competing w/the alternator, they need a more sophisticated strategy to keep the battery charged. For example if the computer realizes the car is stopped, engine at idle, say you are waiting at a stoplight, and the AC clutch is fully on, even though the battery is running down on its charge capacity, the engine computer still won’t allow the alternator to go into charge mode. B/c doing so would further load down the engine, and could cause the engine to stall out. Not a good thing. Better to have a battery w/low charge than stall out at an intersection. Instead the computer will wait until you resume normal driving speed and the AC clutch kicks out, then it will allow the alternator to kick in and charge the battery.

If all that wasn’t working correctly, it could cause the battery voltage to go below the limit at which the car’s sensors would work correctly, and result in drivability problems galore. So if indeed that’s not working, it definitely has to be corrected. Whether that diagnosis is correct or not, and whether the plan to fix it will be effective, no way to tell via the internet. I think you said you’d taken your car to a dealership shop right? If so, that shop if anybody should have the expertise and equipment to fix it. It is sort of unusual for a PCM to fail though, unless it happened during a jump start situation or a battery was installed w/the wrong polarity.

I’m betting if I took my '12 Odyssey w/6k miles on it to that shop, it would also need $3k worth of “repairs”. You need an independent mechanic that targets fixing your specific problem without the 1000pt inspection non-sense…I’ll bet dollars to donuts to PCM exchange doesn’t fix the actual problem. Then later, you’ll be told that you also needed to have your positive battery cable replaced…for example.