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Discussion Starter #1
Yesturday I ran into a charging system problem,Like always when I start my car up I go into enginering mode my battery charge started at 82% within a bout 30 minutes it was down to 62% and the voltage read at idle at 11.0 volts when driving it went up to 12.9 volts.with that said then all of a sudden the check engine light came on and the reduce power light came on?I was able to scan for codes and found a P2105 for the throttle actuator circuit (TAC).Just a coincidence with low voltage from charging system.Don't know.The first thing I did was change the alternator with an O.E alternator assembly.the charging system was back to normal that problem was solved,but the P2105 code did not clear so "back into my pockets I go) needed to replace throttle body actuator assembly,cleared code's problem solved everything back to normal.I can't be to upset since the repair cost for this car for me has been very low.
 

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I have not had a problem with either car yet, other than the car door actuator & gas actuator on the V6. Passenger seat trim went south on the V6 used a tie problem solved.
 

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Low voltage will cause a multitude of issues with these cars. Check your battery, connections and alternator.
 

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Discussion Starter #4
Update:thought we were fine with the repairs new alternator:new (tac)throttle actuator control assembly,but check engine light back on with fault code #p2176;unable to relearn (tac)throttle actuator control;code continuously sets after idle relearn is done.come's right back after car is restarted;going to give it one more shot to do (tac) relearn procedure;if that does not work;then its off to having it towed to the dealership;i installed o.e parts both alternator and throttle actuator,i know that the alternator is putting out 14.3 volts after replacement.what is the chance that it's a defective (tac) throttle actuator.
 

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Update:thought we were fine with the repairs new alternator:new (tac)throttle actuator control assembly,but check engine light back on with fault code #p2176;unable to relearn (tac)throttle actuator control;code continuously sets after idle relearn is done.come's right back after car is restarted;going to give it one more shot to do (tac) relearn procedure;if that does not work;then its off to having it towed to the dealership;i installed o.e parts both alternator and throttle actuator,i know that the alternator is putting out 14.3 volts after replacement.what is the chance that it's a defective (tac) throttle actuator.
Where did you find the tac module? Didn't know they had them separately from the entire TB assy...

Sent from my Nexus 6 using Tapatalk
 

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Discussion Starter #6
My bad; i was referring to throttle actuator circuit (tac) its the whole throttle body assembly
 

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Assuming you have the ability to view your throttle blade position on the engineering page (as I can), you should be able to watch the % value change. With the ignition in the run position, my GT goes from about 22% at idle, to 99% at WOT. For starters, maybe you could see if yours even wants to display numbers similar to that. This, to verify that the blade is at least moving correctly from idle to WOT. If OK, then it says to perform that learn procedure. Was it done as it is written in the service manual ? It says (after performing that learn procedure), to *then* reset the fault code. If it reset (that's good). If not, they pretty much say that the TB needs to be replaced. I find it hard to believe that a new TB was a dud from the manufacture. But things like that can happen. If you have to go that route, I hope the place you got that new one from will allow for a free exchange/replacement of same.
 

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Discussion Starter #8
update was able to return the brand new o.e throttle body assembly for another new one,installed the new o.e throttle body assembly again performed relearn sequence.throtlle body did relearn.code cleared,but when the ignition key is cycled and restart the car the fault code P2176 comes back,tryed the relearn sequence 3 more time it does relearn but when the key is cycled to resart engine code's come back.it maybe time to go to dealer :(
 

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The Mustang dude
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OEM Battery? I just finally replaced the OEM in mine. Wasnt having any issues, but everything works better now. Car cranks faster, accelerates better, shifts better, lights dont dim when I pull all the window switches... everything is better now. Dont overlook the obvious.
 

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Discussion Starter #10
yes oem battery;battery has been load tested state of health of battery is normal
 

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The Mustang dude
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yes oem battery;battery has been load tested state of health of battery is normal
And its as old as the car?
You do realize they have a lifespan, right? They can start cars forever it seems, doesnt mean everything inside it works right.
If your car is as old as mine, its 7 yrs old and it has to be losing effectiveness by now.
 

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Discussion Starter #12
update;car is at the delaer;installed new battery as a precaution even though the old battery still tested good;also disconnected all after market items;dvd in headrest;led light ballest and remote xm radio harness;then we started the throttle relearn protocol precedure and still fault code p2176 keeps resetting within 30 seconds of starting the car voltage jumps to 24volts and idle will not relearn;keep in mind that the throttle body's are new o.e parts were change twice the alternator is a o.e new part;the ecm is new;no fuses have blown;the dealership i have it at i have known them and service my car's there since 1986.i have a very very long relationship with them so i have full trust with them;the tech working on the car i have know him for the last 25 year and is the only tech who works on all my car's;when my car go in for service they don't get bounced around to different tech like some dealers do;he has been in contact with gm technical and has opened a (T.A.C)case which is technical ass't from gm;they have not been helpful to point us in a direction to start looking for a power spike;i am afraid that they may have to start pulling apart wire harnesses;i would not mind if gm technical would give some idea were to start;right now at a lost looking for help
 

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Discussion Starter #13
Update,finally was able to pick up my car on saturday;after spending about a month at the dealer good thing they gave me a loaner vehicle a 2016 chevy tahoe ltz very nice suv;recapping the engine through a fault code for the throttle body;throttle body was then replaced following the service procedure including the relearn process thats when the fun began,as the tech was performing the relearn procedure the car keeped throwing the fault code #p2176,the ignition circuit voltage would jump and stay at 24 volts;that circuit should only be at 12 volts.the car still had the original battery,the battery was load test several time and checked out good,even though it checked out good we replaced with new oe battery,retryed the relearning prodecure again still same issue of the fault code #p2176 setting about 30 seconds into the relearn procedure;the alternator was making a whinning type noise for a couple of day prior to the car going into the shop;we then replaced the alternator with a new oe alternator assembly the whinning noise was gone,now with a new battery and alternnator and throttle body assembly,tryed to perform the relearn procedure again,still after 30 seconds into the relearn procedure the fault code #p2176 sets and the ignition circuit voltage jumps to 24 volts,the tech then gets in contact with gm technical ass't to get some help after spend hours on a confrence call with about 4 engineers they then determin to replace the ecm,we then had to order a new ecm which took a couple of days,the new ecm arrived and then the tech installed the new ecm then proceded to program everything;thinking this would be it,as its being programed the same fault code came back #p2176.wtf this dealer is the exclusive repair shop for all the police"ppv"caprice in the area which include the new jersey state police and port authority and all the local police in the area;unfortunately it was bad timing that i am having this problem because the tech that has been woring on it was going on vacation;i have been a customer of this dealership for over 25 year and i know this tech very well he is one of the best tech at this dealership when people come in for service they always request him to service there car's. Maybe it was best that he was going on vaction because when he came back he would have a clear head,because that code#p2176 is kind of straight foward once the throttle body is replaced just relearn idle,now the tech came back from vacaction and had to remove the fuse box from under the hood and had to expose the main wire harness loom,now it then became a tedious task to now remove wire by wire to see what cirucit the voltage would finally drop to 12 volts,keep in mind that wire harness contains over 100 wires he had to go one by one;after going through them and tightening all the pin connector in the fuse box and the connector end into the ecm the voltage was steady at 12 volts;then proceded to relearn system in less than a minute the system was able to be relearned and no fault code,somewhere in the harnees between the fuse box under the hood and the main harness that goes to the ecm and into the car along the right side fender assembly that was the problem causing the voltage spike;they then called me to come and road test the car,which i did for about 125 miles the car runs like it did when it was new.i am just glad that i did not have to replace the under hood fuse box and complete wire harness;now had the car back for a couple of days and its running great;this was an unusual problem that the dealer and gm technical ass't haven't seen
 

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The Mustang dude
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Glad its fixed but god damn that was a hard pair of run on sentences to read and comprehend.
 
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