Hi all, hoping somebody here will have some words of wisdom on a problem that's been plaguing me lately.

A couple months ago, the battery light came on in my X-Type. Took it to a reputable local mechanic and they determined it needed a new alternator. So I had that replaced. No problems until a couple days ago, when I was on my way to Tahoe and about halfway there, the battery light pops on again.

Not liking the idea of getting stuck on a rural stretch of Highway 50, I stopped off and had a mechanic take a look. The verdict? You guessed it: Need a new alternator. As shocked as I was, I didn't know enough to truly question it, so another $550 (and a rental car and a full day) later, I'm back on the road. For about 100 yards. And the light pops on again.

Back to the shop, where they spent a few hours trying to diagnose the underlying problem, and finally after having tested all the wires and connections between alternator and ECM and battery, determined that I need a new ECM.

Apologetically, they said I'd need to take it to a dealer, because even if they could find a used one, they wouldn't be able to program it.

So, a couple questions: Does this sound right, first of all?

And second of all, from what I've read in the archives here and elsewhere, if I do take it to a dealer, I'll likely be forced to buy a new ECM, correct? If the prices for that are what I'm reading ($1,500+), I feel like there's no way it's worth it at this point and I might have to just give up on my beloved X-Type and find something else.

Any help would be greatly appreciated.

 

I don't believe it, unless they ruined your good ECM. Clearly a bunch of no-hopers.

 

load test your battery and check for voltages losses from the alternator to the battery in the cables. Also, clean and tighten the ground cables under the battery box. I had a bad battery and some tired ground cables and replacing them solved the problem. I'ts pretty rare that an ECM would go bad and cause that kind of issue.

Start from the easy stuff, don't go through throwing expensive parts just because some mechanics are too lazy or inexperienced to diagnose properly.

P.S: check or even replace F82 alternator fuse as well.

 

dudernet, first off, welcome to the Forums. Lots of good information here as you are finding out. But, please stop by the New Member Section and give us a quick intro. You will find that we are a friendly bunch here and we like to get to know one another and make this place more friendly. This will also give you a chance to meet those that make this place what it is.

As for your problem, it is possible that the ECM has an intermittent problem and it results in either the alternator getting too much field (which will lead to the alternator getting too hot and eating itself) or the ECM sees the voltage as being too high (when it reality it is not) and it lowers the voltage to the point that you are now sucking power off of the battery. This is where some knowledge and use of a multimeter can differentiate between the two. How are you with a multimeter? I can step you through what needs to be done.

As for getting the dealership to reprogram a used module, that will depend on the dealership. Some will do it, some won't. Do some calling around. Members here have gotten a used module programmed with no issues. In some cases, programming is not required because the module was programmed close enough to the original computer that it swapped out without any issues.

Like ArmXT said, it can be something else. Keep in mind that our cars suffer from bad battery cables and that can cause what you are seeing. Again, if you want to check those yourself, I can tell you how to. It could also be the wire going between the ECM and the alternator has gotten a high resistance connection in the middle of it somewhere and that is causing the field to not be as strong as it should be.