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Old 02-01-2009, 09:41 PM   #1
S Dee
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Join Date: Jan 2009
Location: Aurora, ON
Posts: 14
Fault Code 1-2-3-1

Hey guys, I'm new to the forum here and I'm hoping someone can help me out with an issue I'm having in my 1994 318is. As the title says, the car is throwing the fault code 1-2-3-1. I know it's the fault code for the DME main relay / battery voltage. I've been trying to track down the source of the problem with no luck.

The check engine light will randomly flash on and off every once in a while for a brief period. The light will come on for about one second then disappear. Sometimes it will go problem free for days and other times it flashes many times within a minute. However the light never stays on all the time. Every time the light comes on, there is excessive voltage running through the car, because the headlights get brighter (almost like high beams), the A/C and heating blower fan starts revving faster, and even the windshield wipers will work faster. The voltage only seems to go up for these short one second periods - triggering the check engine light. It sometimes causes the dash lights to go out and most of the time causes the aftermarket stereo to cut out, due to this surge in voltage.

So far I've had the alternator checked out to be good and the battery has also been replaced. I've pulled the DME out of the car - the DME compartment is dry, but the case for the DME as little spots of corrosion on the aluminum as if it's been damp in the past. All the connectors on the DME and wiring harness plug are also clean and corrosion free.

Sorry for the long winded explanation, but does anyone have any suggestions as to what might be causing these voltage surges? Is it possible for the DME to cause these voltage spikes? Any suggestions would be greatly appreciated. I can't think of anything within the car that would cause the electrical system to produce excessive voltage.
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Old 02-02-2009, 10:18 PM   #2
FunAndEZ
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Its probably your voltage regulator on the alternator. I had the exact same symptoms and that was the cause.
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Old 02-04-2009, 07:09 AM   #3
S Dee
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Quote:
Originally Posted by FunAndEZ View Post
Its probably your voltage regulator on the alternator. I had the exact same symptoms and that was the cause.
That's what I was thinking too. When I took the alternator to a shop that specializes in rebuilding them, they said the alternator is fine. They also said it's impossible for the alternator give the symptoms that I was describing.

I think I'm going to take your advice and replace it. You're the third person who has suggested that to be the problem. I think it's time to ignore the guy at the shop and go ahead with it.

Thanks
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Old 02-07-2009, 03:57 AM   #4
FunAndEZ
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You dont have to replace the whole alternator, you can replace just the voltage regulator, its a removable part on the alternator. But you might as well replace the whole thing.

It is definetly your voltage regulator. I had the same error code and everything. The guy at the shop says the alternator is working fine cause it is working, but its probably spitting out some high voltage because the voltage regulator on it isnt working.

If you keep running your car like that, you could cause your battery to leak, not to mention a number of other problems.
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Old 02-07-2009, 07:17 AM   #5
S Dee
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Thanks for all the advice. I've been searching all over the internet for the longest time to try and come up with some answers for this and haven't found any relevant suggestions. I'm going to try and track down a regulator today. I know it's not a good thing when I get these spurts of high voltage. I've been extremely worried that I'm going to blow something else in the car with the voltage surges.

Thanks again. I'll post a comment with the results after I change out the regulator.
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Old 02-13-2009, 02:30 PM   #6
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Old 03-29-2009, 10:26 PM   #7
S Dee
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Quote:
Originally Posted by FunAndEZ View Post
You dont have to replace the whole alternator, you can replace just the voltage regulator, its a removable part on the alternator. But you might as well replace the whole thing.

It is definetly your voltage regulator. I had the same error code and everything. The guy at the shop says the alternator is working fine cause it is working, but its probably spitting out some high voltage because the voltage regulator on it isnt working.

If you keep running your car like that, you could cause your battery to leak, not to mention a number of other problems.
To follow up on this post (I hate reading through forum posts looking for possible remedies to problems and never knowing what the actual fix was in the end), I swapped the voltage regulator about two weeks ago and haven't had a problem since. The problem usually would have surfaced again many times by now. What a cheap easy fix once you find out where to get the part from for cheap. The dealer's list price was $220, but I ended up getting a local alternator shop to order in an aftermarket one for $40 cash.

Thanks so much FunAndEZ... it seems to have fixed my problem.
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