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04 buick LeSabre 3800 intermittent high voltage and voltage drop when shifting

  • Confidential 007
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15 Sep 2021 00:12 #51433 by Confidential 007
04 buick LeSabre 3800 engine. Main concern is high voltage at highway speeds and at start up being at 15v. Second concern is voltage dropping to battery voltage 12.9 (12.9 bc its overcharging) then with a little rev of the engine it will go back to 15v. Put it in drive and another voltage drop. Going from park to reverse is more pronounced voltage drop.. new iac valve, new front transmission mount, cleaned throttle body and egr, new spark plugs and wires. Tested coil pack with the danner method and is ok at idle but couldnt test coil pack under load.

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15 Sep 2021 14:25 #51436 by scannerjohn
Where and how are you getting these voltage readings?

"an open mind let's knowledge flow in and wisdom flow out for a man who has neither never listens to those who have both".

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15 Sep 2021 14:36 - 15 Sep 2021 14:42 #51437 by Confidential 007
I first noticed on the dash gauge the voltage drop and then hooked a multimeter to confirm and surprising enough the dash was very accurate and read the same on the multimeter. Did a voltage drop on all charging wires expect starting wire and didnt have a voltage drop on the wires. The battery cable from underhood fuse box to battery under the seat. That cable actually has a crimp in the wire like someone put the seat on it and flattened it a little bit but its saying no voltage drop on the wire reading was .09. i forgot to mention in the post i have a power steering pulley that doesnt spin as freely as it should. I just got the car not too long ago and trying to get it all together. My main concern was the high voltage especially at highway speed where the alternator should be working only at 10% but the voltage is 15v. The battery is under my back seat where I have children so i dont like the high voltage and im assuming the voltage drop may be a culprit. Also checked the alternator harness wires. I have good ground, 4.8v on my reference and 3.6v at the signal wire when at idle. I didnt do a voltage test on the signal wire bc i have nothing to compare a good voltage to. Thanx again to all u guys
Last edit: 15 Sep 2021 14:42 by Confidential 007.

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15 Sep 2021 17:30 #51438 by scannerjohn
Looks like a bad voltage regulator in the alternator. Put red lead of volt meter to the B+ post of alternator and black lead to ground. Switch meter setting to AC volts. If reading of .25 to .50 alternator is bad.

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15 Sep 2021 18:04 - 15 Sep 2021 18:17 #51440 by Confidential 007
Sorry i starter the explanation on youtube and mentioned it but forgot to mention it here that i put a new alternator in and still had the same issue bc my first thought was the regulator. Also put a new battery in bc this one is older but still same readings so i returned the battery and alternator.
Last edit: 15 Sep 2021 18:17 by Confidential 007.

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15 Sep 2021 18:33 #51441 by ScannerDanner
Man, I was wrong on this system (we talked on YouTube for other reading this). You were right about what you read in you Haynes manual! I really hate those manuals and let that dictate my thoughts lol

From looking at the diagram the Dash Integration Module is the one that is the brains in the system BUT it is NOT the one controlling the alternator. The ECM does this on the gray wire (pin 29) "Gen Field Duty Cycle Sig" and then it also sends a turn on or wake up on the red wire (pin 61) Gen Turn On Sig. 
The Dash Integration Module talks to the ECM via a class 2 network and tell is what to do based on the two inputs it sees on (pin A12 and B12), these are simply battery voltage and battery ground inputs. This is where we need to focus in my opinion based on your symptoms. 
So we need to take direct measurements from these two locations (if possible) and compare to what you read directly at the battery. 
Do you have the ability to see data on the Dash Integrated Module? If you do, then we can maybe skip this step (direct measurement), at least initially.  
 
We have to be careful sharing service info here. If you need additional help with this as far as component locations and other service info. Here is a link to the DIY version of this program that I am using. eautorepair.adtrk.biz/?a=10817&c=24&p=r&s1=

Don't be a parts changer!
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15 Sep 2021 18:43 #51442 by ScannerDanner
I think you may have a poor signal getting to the Dash Integrated Module (low voltage on the battery positive sense wire or poor ground on the ground sense wire) we need to measure these to confirm. Also do the measurement I am calling out in this pic, this will answer the "low voltage here" (at the fuse) I have stated in the pic because it is shared with the alternator on that pin and the DIM. 
Also as an easy thing to do, that battery ground cable, right at the battery, is a split cable and right where they connect together, we want to take that apart and clean those areas really good.

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15 Sep 2021 19:07 - 15 Sep 2021 19:17 #51443 by Confidential 007
I do not happen to have a scan tool that can read that data. I only have a 20$ obd2 that i can use with an app but it doesnt communicate with modules. I can read the voltage at the sources. I have the same exact manual u have actually, now i realize its not a hanes manual. But anyway i can get a reading. So ground and power at the dim and ground and power at the ecm ( on those pins of course) and compare to battery voltage correct?      Side note after watching hours apon hours of your videos for the last year and a half and having no mechanical experience i am proud of myself that this is the direction i was going in which is a hard diagnosis bc most cars its just the regulator or ecm controlling it and also so grateful for the experience in diagnosis ive gained by watching your videos. So much more to learn.  Not trying to kiss ass btw just honesty.
Last edit: 15 Sep 2021 19:17 by Confidential 007.
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15 Sep 2021 19:16 #51444 by ScannerDanner
I'm just glad you are here and glad to help! And I didn't even know that part of your story. I never get tired of hearing how much this helps others. Looking forward to the results of your tests.
Thank you!

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15 Sep 2021 19:19 #51445 by ScannerDanner
Something else that is VERY important. ALL of your voltage measurements should be compared directly to battery ground, right at the battery, NOT the frame or body especially because of the remote location of the battery. And when you do your ground tests, it will be ground to ground voltage drop tests NOT resistance okay?

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15 Sep 2021 19:54 #51446 by Confidential 007
Yes sir i watched the video on how important voltage drop testing is and not relying on resistance in a wire for an accurate reading. I will game plan tonight on all my steps to take and will do measurements tomorrow and get back with the forum... I cant thank you enough though for all of your time.. i didnt want to put a sob story but my father passed away 2 years ago and he was a GM mechanic his whole life. I made the mistake of not gaining knowledge in cars from him bc i wasnt really into it. Then when he passed and my car started breaking and my mothers car, i turned to youtube and found scanner danner and man u made me fall in love with diagnostics. My dad never tried to force it on my so thats why i never really gained the knowledge back then so it was completely my fault. Now i wish i could talk to my dad about cars and hes not around so its cool watching your son soak up your knowledge the way it should be, i was just too hard headed back then. So no sad story, i was there for my dad until the end and death is promised to everyone so i remain positive but we all one day will just want one more conversation. Just a reminder to appreciate the people around you. Have a great night everyone

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15 Sep 2021 19:59 #51447 by Confidential 007
I also just seen the second message on the negative cables and the measurements there to be done. Will do sir. Thanx again i will get back with you guys tomorrow on all my findings. U are the man bro

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16 Sep 2021 08:37 #51457 by jreardon

the Dash Integration Module is the one that is the brains in the system BUT it is NOT the one controlling the alternator. The ECM does this on the gray wire (pin 29) "Gen Field Duty Cycle Sig"

Hello ScannerDanner. I have a question. I could be totally off and maybe this doesn't apply to this particular alternators operation but I have in my notes that the F terminal just tells the PCM about alternator load.

During the late ’90s, we started seeing the L terminal on the CS series four-wire regulators connected to the PCM, as well as the F terminal. This led many techs to assume that the PCM controlled the field current, as it does with Chrysler. It does not.

www.motor.com/magazine-summary/are-you-s...art-charging-system/

Dave Hobbs explains as such @ 2 hours 19 minutes in this Youtube video:

 

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18 Sep 2021 20:05 - 19 Sep 2021 01:57 #51543 by Confidential 007
Ok guys. Sorry been busy with work. So far i have measured voltage at connectors a12 and b12 of the DIM module. Orange wire (a12) to ground on battery, same as battery voltage. I was reading 14.67.. ground (b12) to ground on battery was weird to me bc it read only 0.00. check my connection and still 0.00 on ground... Cleaned the negative battery cable (at battery) and could not get in-between the wires that are connected (at neg terminal) so i just poured coke in it... Battery voltage at the b+ and grounded to battery was the same as battery voltage as well.. i have a new charging cable that connects to the b+ of alternator, to starter and then to the fuse box. But im getting voltage drop on the wire between the b+ post and battery negative. from b+ to batt neg terminal its .23 to .28. but from fuse box to bat neg cable it reads .09 ... when i put it into reverse and the issue occurs with the voltage dropping to 12.9, the .23 also drops to .09...  Car was already warm so my voltage wasnt as high as when i cold start and its at 15v and couldnt do a highway speed test (which is when the car is at 15v also) .. Voltage at alternator (orange wire) to neg terminal was same as battery voltage... my next test is that ground wire that goes from battery neg to a ground distribution harness connector to DIM.. then maybe backseat fuse box wires (orange) then ecm.. that one voltage drop from the b+ to the neg terminal, i dont like it being .28. idk if it relates but havent checked any voltage drops to the starter yet..Again cant thank you guys enough
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Yesterday 15:19 - Yesterday 17:50 #51593 by Confidential 007
    Today i was testing voltage on these wire (pic inserted) i also just happened to test the daytime running lamp relay control. Everything mentioned on pic was the same voltage 14.7.. but the drl relay control wire was 15.23.. the control output wire (b8) was 14.23.... Led dimming signal was 10.4 key on engine off. Everything else was measured engine on. i think i might be onto something. Jus not sure what now lol. 
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