Lately I’ve been seeing some voltage fluctuations on the dic sometime the security light comes dash lights up like a Christmas Tree. Voltage used to be a stable 14.7. Now they are 13.5 and I have seen 11-10 sometimes when blasting the A/C turning on my fog lights / headlights it will stablize sometimes back to 13.5 but jump around. When laying some throttle a a random jump at idle. I have noticed the the battery contacts seem to be dented in maybe causing the a small ark or something bad contact ? Or just the alt is had it’s life as it is the original with 124k on it !

Im gonna rip it down on that side and replace some battery & terminals + & - . Buy a new alt anyways.

 

First thing I’d do is connect a voltmeter to the alternator B+ terminal and check your voltage there...see if it’s low or fluctuating...I’d then do a voltage drop check on the positive and negative side of your charging system...red lead of DVOM to battery positive and black lead to alternator B+ stud...you should not see more than .3 volts or so...to check negative side red lead to battery negative and black lead to the alternator case....0.1 to 0.2 is good...I’d try that first...the DIC voltage is usually around .5 volts lower than charging voltage (DVOM across the battery terminals).

 

Brought battery back had a 5 year warranty. Tested bad. Replacing side post screws as they are stripped out.


Thanks I’ll test the alt if problem persist after this basic maintenance.

 

New battery and side post and removal and clean up of the lower ground under the battery tray has solved this issue. I’m still ordering a new alt anyways just for the sake of it being being new

 

If your alternator is fine, be careful with an unnecessary replacement. This could open Pandora's Box: plenty of horror stories documented here!... In any case, DON'T turn in your old alternator as core.

If you are concerned with the car's mileage and the normal wear on the alternator, check the links at the bottom of this post for rebuilding information. Perhaps all you need are new brushes.

Take a look at this post for an in-depth analysis of the C5 alternator.

What makes this alternator so peculiar is that it is excited when its regulator receives a turn on signal of 10v at limited current provided by the PCM through the L wire. Not all regulators accept the turn on signal provided by the C5 PCM.

Another distinctive attribute described by Lionelhutz in this post:

For a potential rebuilt route, take a look at this post. It has info on the right regulators for both, 97-01 and 02-04. The price is around $30.

This other post has detailed info on the rebuild procedure and links to get the other parts.

 

Pcm is spent no comm it wouldn’t reflash either . All contacts are fine . Pcm is no bricked . It showed all the signs .147 for a new one with a life time warranty P01 .

 

So after unhooking the battery pulled fuse 16 & 23 while the car was on acc. Waited over night reattached in the morning. Hooked up hpt tuners just for the heck of as one last hurrah before taking out the pcm. Clicked Write calibration from a older file File wrote fine. Ok Now rewrite entire boy I hope so. Wallah car starts first turn no lights all seems to be gravy for now wow it was a close one for those who have lost comm during a write I hope this helps out.

 

why did you rewrite the tune if you were just replacing the battery and terminals??

 

I was facing some voltage issue and a security light would pop on randomly. It was buggin me . So I exchanged the battery and cleaned the grounds added some new post as the 1 was just about stripped . Voltage stayed stable that dam security light kept coming on. After I had locked my keys in a few weeks ago I figure well maybe it’s in anti theft mode. Cause I am getting a P1626 code. So I figured restore to earlier point in its life when it was richer anyways . Pcm bricked and unbricked. Drove it around same code . Inspected the fuel wire on the firewall . No comm to pcm on the Dic yet the car will run fine .

Shut the car off just now inserted key re wrote calibration fine back to where it was. However I’m sure the P1626 is bound to come back along with all sorts of service lights. I think the pcm has lived it life and shorts out. Or it’s possible something to do with ignition and I will do the 11 minute process see if that helps. If it’s a no go I’ll change the ignition over to a push to start with passive keys . Next would be to change the pcm and the one inside the car. The

 

Also try cleaning as many ground connections as you can find. Search forum there are threads with all the ground points.

 

Most likely the ignition or wires somewhere lays the problem. No light today when I had it out . I cleaned the prongs on key.


If I get into hpt and put it to no error reported it should never be seen again.