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ECU/alternator problem

92briarwoodjhall

NAXJA Forum User
Location
Arcadia, IN
I have a 1992 briarwood and it threw a code for alternator field control so I went and had it tested and it passed then I was reading and i read that it has an external regulator built into the ECU and I was wondering wether I could wire in a regulator or if I have to buy a new ECU.

Thanks
 
Was it a code 41? Every 41 I've seen so far has been caused by the actual alternator itself.
It's possible that it passed testing, but is starting to fail.....
 
Had the exact same problem. Code would come and go. Mostly when I started in morning. The brushes on the alternator were worn (one more than the other) and would not contact properly. As said replace alternator or change brushes.
 
I'm sticking with my guns and still betting that at the end of the day, you'll find out that the problem is the alternator.

Many OBD codes require some pretty serious interpretation, but I've never seen that with a 41.
 
Did you have it tested at an automotive electrical shop or at parts houses (Autozone, O'Reilly, etc.) If you haven't done so, take it to a shop. They will do a proper test and if necessary, repair it for less than the cost of a replacement. Been there, done that.

Aside from the CEL and code, what is your voltage gauge showing at various times -- start-up, etc.

And, your business, but I would not rush out and replace the PCM until I had a test from a proper electrical shop along with my own meter readings.
 
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Tested it everywhere. My voltage gauge only reads 10 ish and sometimes after a while it will kick up to 14. Tested at battery voltage was only getting 12 v and tested coming from ECU and didn't get any reading. I just don't know why it's throwing the field control code if it's not a regulator. I'm gonna buy both and out alternator on first and see. I can get a ECU from O'reilly for about 150. And alternator for 100.
 
Let me expand on my previous post. As I said, had the exact same code. It was intermittent. When I turned the XJ on it would give me the code but if I restarted it would go away. I opened up the alternator. Found the brushes worn and dirty. I cleaned it up and it ran fine for another 3 months. As soon as it threw the code again I had the brush assembly to change out. Months after I have no problems.

I have seen the ECU go bad but never in that way. Not saying it can't happen but as others said its much more likely to be the alternator!

Good luck.
 
Now that I understand your reply better mine is doing that same exact thing. It just kind of threw me off when it tested good every place I went. It makes sense now.

Thanks everyone.
 
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