carls2004

My 2006 uhg.
Long story short.- I took out my aftermarket Head Unit and installed a Alpine head unit. And added the PAC unit that wire's in behind radio to fool deck that ebrake is on.. THEN after starting car ABS light came on..and code of C0121..... I rechecked everything, and all i could figure is it was a fluke and my ABS unit took a crap. So ive been ignoring it and driving car for x amount of weeks.
Now this morning i get in the car and start it and dash shows E brake is on when it isn't and serv veh pop's up . And then i lost most of my steering assist..
So at work this afternoon i finally was able to check voltage to ABS (OK) and scanner said unable to communicate with ABS, and ECM is unable to communicate And i have a code of U0121...Rechecked fuses, (good).
So any info would be great guy's... Im still thinking ABS unit.

AORoads

I'll add a not of levity since I know not the answer to your question(s).

Computers! Can't live with them. Can't live without them! Yours are not "talking" to each other nicely. Big OOPS.

carls2004

Thanks for response..I ORIG started with CO121, and just been driving veh living with light on. Then this morning boom loss of steering assist and e brake light on, and other code now.. Just dont have funds to guess and start replacing parts.. Hope someone jumps in and gives me some input. as im aiming that the ABS unit is still my culprit.

Kenny94945

Strong chance it is related to your install.

You are looking at a lot of electrical testing that IMO the 'net really can't answer for you...just start picking wires and tracing etc. Would really need a service manual for efficient searching of electrical valuations.

You mention budget.

I offer that you remove your new deck and especially that PAC unit and re-install your old deck. Then you have a base line and move forward with testing. Will you still have the issues with the old unit?

Goes without saying (almost) look for pinched, pulled, damage wires from your install during this reverting exercise.

Lastly, many say low batteries are a Vette nemesis.
So make sure your battery is good and or new.

Good hunting.

carls2004

Thanks..
I did orig remove new deck and unhooked when i got the first code of CO121, and see no issue of anything wrong with install.... Or possibly my first PAC unit was defective and somehow killed ABS module but without seeing wiring diagram i dont see how it could of sent a short ? to kill ABS and set that one hard code.
So then i put the Alpine back in with a three wire Pac unit which is pretty simple. ground, acc power, and signal to deck wire only to fool it that ebrake is on.
When i first swapped deck i did foolishly forget to unhook battery and i possibly could of hit acc wire to ground when i cut wire's....and power was still active.. But you would think that would of just blown fuse...But dont see how ANY of that could tie into ABS...????????.
Now i wonder if the OS-2BOSE unit that is in veh that keeps all options of veh working with aftermarket deck, is anyway damaged ?. BUT again i cant find any info that shows radio wiring is tied into abs..

carls2004

Bump... Any other thought's. ?

TnRZ06

Im not great on electrical, I did my own install of the pioneer nex 8000. I believe I just grounded the wire that tells the unit e brake is on.Im thinking that what ever you did to fool the unit the e brake is on is fooling the car to thinking the e brake is on thus all the problems with abs system. My system works awesome and can play movies while your driving.Im sure with the guys on here someone will chime in.I would also post this on the stereo section of this forum I had a guy named Mark help me there he knows the electrical inside out. I hope you get it straightened out these are awesome rides

carls2004

Im not sure how your NEX 8000 wire's up,- BUT .On the Alpine there is a ebrake wire coming out of the (deck) harness. And to fool deck (not car).. you add a Audio Video Bypass, and that send's signal to (deck) (not car ) that ebrake is on..
So i did remove everything and still ABS issue which leaves me ?..
Was it a fluke that code came in that points to bad ABS UNIT or did the orig PAC TR7 unit i added that has alot of wire's kill the ABS module ?.
SEEM'S impossible as it only sends a bogus ebrake signal to deck not the car.
Then weeks later driving car with abs light on,, it decided to go worse with a different code and say's no ECM communication now with ABS..And i lost the steering assist as whole system is down... Just so confusing. As i cant seem to see how the wiring for the sterio and how you add the video bypass can or could mess with ABS.

TnRZ06

Try to get Mark on the stereo section, also check for wires going from your wheel hubs to see if there is cracks or if they are broke. I have never looked at mine so I cant say where the sensors are installed.

carls2004

I posted in the audio. thanks..
Before issue went worse i had scanner on car and all showed good besides code and i can communicate with abs and ecm. and all wheel speed sensors were being seen by scanner and operating.. But i should do a peek i guess anyways at them with my own eyes.

kcbc

time to see a real mechanic...not guessing any more ....

Wampa

I'll take a shot since I; like you, have been modding stereo etc for most of my life (vette included) and run into "weird" things before and been stubborn about undoing all of my work that I just knew "wasn't the problem". I can tell you that for you; or anyone else, to have a good shot of tracking this down you need to remove ALL aftermarket connections to the car. So not just the radio connection itself, but all PAC interfaces etc. Also, did you splice into any of the car side of the harness to install these things (or did they all simply plug into factory pin connectors?) Remove negative battery cable before beginning your removal; then reconnect once EVERYTHING aftermarket is out. Test drive and report back. If you seek professional advice; you should take it with aftermarket equipment out of the equation--too many unknowns added there to efficiently diagnose. And yes; even if it makes NO SENSE. I think you may find that there is a much cheaper solution to your problem then replacing modules--communication issues could be coming from mods....or maybe not...but best place to start and will make it easier to find root cause if they are not it. Best of luck, looking forward to hearing what you find out!

carls2004

Thanks.. And yes i did undo and remove what i did on the sterio install and then erase orig code that was there....But still same issue BUT i did forget to unhook the PAC OS-2C BOSE that already existed with orig aftermarket unit.. So unhooking that is my next step and then there will be just a open hole in dash like the stock H.U. was just unplugged and missing...
As for cutting into anything i didnt have to as there was the PAC OS-2C INTERFACE already there with orig aftermarket unit and the veh side of harness plugs into that ..
I completely understand how hard and/or being able to say what it may be,, as i i know how elec can be a tuff issue at times As i was a 30 year Chrysler Tech and electrical was my week point...but was just looking for thought's and input. Ill keep ya posted after i unhook the Bose interface unit..

carls2004

For me that is a crap response... --Always one in the bunch..
As i was second lead Chrysler Tech in North East 3 years' running and worked 30 year's at it..but elect wasn't my strong point and cars have gotten harder in that area since 2000....
All i thought was maybe im looking over a simple issue or someone may have ran into a similar issue.. That is one reason for these forum's...and my question's....
So with that kind of response you should of just skipped by my post...And i bet a whole lot of other member's post..

kcbc

you should check if your radio is part of the network for your data line if you are a 30 years tech...... I know I kicked enough people out of my shop on most gm mid 2000 car when they place after market stereo and when needed during recall or repair --> it cant be reprogram !! --> cause network problem block it !!!! .... electrical and electronic is what today mechanic all about .... all else just changing parts for luck ....any1 can do that

BigBlok502

What is the purpose to fool the head unit the E Brake is on? I thought the PAC units main purpose was to allow aftermarket head units to work with the Bose ancillary components. When I installed my Kenwood, the only thing I did out of the ordinary is make it think the car was in reverse all the time so that I can switch on the rear camera whenever I want to.

Have you checked the switch for the E Brake that indicates whether or not the E Brake is on? Perhaps it is indicating the E Brake is on when in fact it is not on.

carls2004

I think your thinking of the Pac Interface...??? Im talking about the PAC TR-7 or the better unit Micro ByPass which i have in there now..

It is to allow video to work while driving,, and give you availability to get into all the settings without E brake on...as i guess Alpine gives you less availability to get to them unless E brake was on..
Ive check that E brake switch also...
Im gonna try to get back to car tomorrow and get the PAC OS-2C BOSE interface out and erase code and see if it pop's right back up..

BigBlok502

Thanks for the clarification about watching video etc.

When the E Brake is pulled up and activates the micro switch, the micro switch supplies a ground which in turn activates (turns on) the E Brake lamp. Very simple circuit.

For troubleshooting, as had been mentioned, the best thing you can do is eliminate the aftermarket system altogether by taking it out of the car. It is hard for me to believe the PAC system you have installed is back-feeding into the ABS unit, however with it removed from the car, along with the head unit, you have eliminated that as a cause for your problem. (That is if the problem still exists with it all removed)

carls2004

I thought the same thing that it is hard to believe Pac unit or my micro E brake by pass is culprit. But i will get back into dash today or tomorrow and get everything out (everything) .. Then when i get to work ill get it on scanner to see if all issues still present..

Old Ben

Bypassing the system so that you can watch video while driving? Sounds about as sane as texting your way down the road. Just my opinion but there are enough distractions already.

They have that safety feature on the system for a reason.