Question: C6 codes.

[Best Vette Yet]

I have a 2005 C6 Auto, 4800 miles. Purchased Sept, 08. Vette went great until battery died. Replaced battery. Since then, every fault code in the book appears. Service traction control, shocks inoperative,etc. windows will not close up after entry, drivers window rolls down 7/8 of the way. Vette will sometimes not start and the gauge cluster will go dark, then come up on its own. Check engine light comes on. When the car is running, on a good day, all is well until something like "traction control" is activated on a wet patch of road. At this point, all hell breaks loose, power is cut and I have to pull over and power down for 30 secs. The vette will not always start up again so I have to sit and press the dreaded button over and over again. I have had the vette in pieces, have checked nearly all the wiring, connections etc. I can find nothing loose or unusual. I do not drive it anymore for fear of being away from home and stuck in a mall lot. I use the key to open it up. I have replaced the batteries in the fobs as well. There are no mods on the car, everything is as is from the factory. I have PM'ed c4c5 so I am hoping for an answer soon. In my PM I said the car had done about 18K, I was mistakes, typo error. Any assistenace would be helpful. I have read other posts about starting problems but mine seems to be unique...just my luck eh. ad

 

[NORTY]

With all those problems, it stands to reason that it's something common to all of them. You may have to replace the battery again. (Just because a battery is "new" doesn't mean it's any good.) It could be an internal problem with the battery. Do you have access to a voltmeter? I'd start there. Then I'd move to the ground strap connections. Could be a weak cell also causing voltage loss/spikes. Is the battery of the right size/capacity?

Did one of the cables touch the wrong post? There should be some codes to decipher, have the "specialist" look into it for you. He has the books, I don't. Be sure to tell us what is found.

 

[c4c5specialist]

HI there,
Yes, the battery could be the common denominator here.
As 'norty' explained, just because the battery is new, doesnt mean its good.
Honestly, what would be suggested, is to clear the codes and road test the vehicle and see what codes come back.
That would be my first suggestion.
Torque on the battery cables is critical to prevent distortion of the cable terminals.
That being said, 71 in lbs is the correct torque.
Allthebest, c4c5

 

[Best Vette Yet]

I have measured the voltage, it is 14.5 with the motor running and 12.6 with the motor off. The dealership installed the new battery and has done a current draw on the battery which tended to be in the region of 700 Amps. Where are the ground straps so that I can re-tighten them down? The battery terminals are tight tight, there is no movement. How do I cancel codes on the C6, I do know how to cancel codes on my C5, is it the same principal?

 

[c4c5specialist]

HI there,
Codes should be recorded and checked.
No, owners cannot do it unless they have a scan tool for ALL modules.
However, you might want to take a look at the codes while they are extracted by your service technician and write them down.
Allthebest, c4c5

 

[Best Vette Yet]

Thank you Paul,
I will have the codes scanned. asap. Any luck on the location of all the ground straps on the C6? I wish to tighten them down as well. I will inform you of the codes as soon as they are available.
Michael

 

[c4c5specialist]

Hi there,
Concentrate on the ones that are on the engine block, and passenger side frame rail below the battery.
Allthebest, c4c5

 

[Best Vette Yet]

I have had the codes scanned, the dealership used a Genisys SPX OTC scanner. Codes are U0001C and P0700A. Dealership also reset the codes so I will wait for an answer from you before pursuing. I have tightened up all the grounds as you suggested. ;help
Michael.

 

[c4c5specialist]

I have had the codes scanned, the dealership used a Genisys SPX OTC scanner. Codes are U0001C and P0700A. Dealership also reset the codes so I will wait for an answer from you before pursuing. I have tightened up all the grounds as you suggested. ;help
Michael.

WHAT?????|
You had the U0001C and they did NOTHING about it????
OMG, well, this shows a short in the CAN communcation line.
That being said, either there is a bad module or the wiring is shorted to battery positive voltage or one of the line resistors is bad.
That is causing all your traction control issues, because the traction control cannot communicate with the PCM or the TCM.
P0700 is a direct result of the U code setting.
And I have NO idea why they are not using a Tech 2 with a Candi module to validate and confirm communcations with modules.
What modules was the U0001 set in??
Allthebest, c4c5

 

[Best Vette Yet]

Hi Paul,
I am annoyed that the technician wiped the codes. I will have to sit with the vette now and try to get it to fault again. I have had a flawless Sunday with it and have driven it hard. On Saturday, I reversed out my drive, there is a slight dip before the street. I presume now, from your comments, that the chassis may have twisted slightly on the way out as the traction control warning came on....the vehicle was in reverse and doing 2 mph. I do not know what other modules were involved but the tech did say that the code appeared four or five times in the system. I will be changing dealerships now in response to your message. If you were working on my vette, what would be your next step to trouble shoot this problem? I have called around for a price and to replace a harness with a break in it, including labor, is a few grand. I do not have that capital available right now so any advice will be appreciated.
Michael. ;help

 

[Hib Halverson]

I first wanted to ask, since you tightened all the grounds, have the various service lights come on, again?

It's obvious you understand the need to change dealerships. A GM dealer using an OTC in that diagnostic situation is unconsionable. A Bosch TECH2 is a required tool for any dealership. You can't fully diagnose C5/C6 without a T2/CANDI or at least a Bosch Mastertech with the CANDI module.

Knowing your budget constricted, you're in a tough spot because you really need the factory service manual and a T2 to properly diagnose and locate the offending parts of the harness or connections that are causing DTC U001C. Without a T2, you're going to have a tough time getting the info c4c5specialist asked about.

It is true that labor on tracking down wiring and connections problem can be expensive because it's often "straight hourly" work.

It's so unfortunate for the DIY that, with C6, GM elected to discontinue on-board display of DTCs by module. It really puts DIYs attempting advanced diagnostic projects out in the cold.

 

[c4c5specialist]

Hi Paul,
I am annoyed that the technician wiped the codes. I will have to sit with the vette now and try to get it to fault again. I have had a flawless Sunday with it and have driven it hard. On Saturday, I reversed out my drive, there is a slight dip before the street. I presume now, from your comments, that the chassis may have twisted slightly on the way out as the traction control warning came on....the vehicle was in reverse and doing 2 mph. I do not know what other modules were involved but the tech did say that the code appeared four or five times in the system. I will be changing dealerships now in response to your message. If you were working on my vette, what would be your next step to trouble shoot this problem? I have called around for a price and to replace a harness with a break in it, including labor, is a few grand. I do not have that capital available right now so any advice will be appreciated.
Michael. ;help

HI there,
I am NOT convinced you have a broken harness!
U0001 is a short circuit code but the subcode, if there was one, would tell you WHAT TYPE of short it was.
This is what a Tech 2 give you that other tools do NOT!
DETAILS!
That being said, the key is in the diagnostics.
Personally, what I would do, is to extract all codes from all MODULES.
This will tell you WHAT MODULE created the condition or if all the modules have the same code, then maybe it would be a wiring issue.
The key to understand with the wiring is that the CAN line is a 2 wire communications line, with terminating resistors on both sides.
These run from the ECM, TCM, ABS, BCM, Onstar, and F55 suspension if you have it.
So, you have taken it down to 6 modules. That being said, your ABS is in your engine compartment, but the F55 module is in the back of the trunk.
Elimination of these, one at a time is how I would proceed.
Allthebest, c4c5

 

[Best Vette Yet]

I have taken the vette to a third dealership and talked with the Supervisor / Manager. He says that due to vette having very low miles for a 2005, he will diagnose and perhaps have GM share the costs 50/50 on the repair. He says that these symptoms are not common for low mileage vettes. Before I took the vette in, I managed to bring up all the relevant codes and showed the service tech the codes on the DIC before powering the vette down. Hopefully this helps as the faults do not duplicate themselves at the dealership. I will hear this evening how things went.confusedbash:bash:bash

 

[Best Vette Yet]

Now for the rest of the story....I took the vette to the new dealership, here is the story: "Tech scanned data, found 20 communication codes. Cleared all codes and test drove. Codes not coming back. Checked grounds, ok. Tech found 1 document matching concern. Ground above starter and below manifold ok. Unable to duplicate concern. Codes: U2108,U2107, U2105, U2100, C0895, U1017, U1024, U2106, U2112, U0001, U0101."
This is all the info I have. I took the vette out with the service tech and gave him a white nuckle ride, he left his finger prints implanted on the oh s@#$ handle, did a couple of donuts....I could not duplicate the fault. Traction worked, active handling worked...no codes.....I hope it is ok now. The tech spent 7 hours on the vette, they charged me for one hour diagnosis time; my good. Please let me know what the codes mean, they are not listed on the net for the C6 vette.:W

 

[c4c5specialist]

Now for the rest of the story....I took the vette to the new dealership, here is the story: "Tech scanned data, found 20 communication codes. Cleared all codes and test drove. Codes not coming back. Checked grounds, ok. Tech found 1 document matching concern. Ground above starter and below manifold ok. Unable to duplicate concern. Codes: U2108,U2107, U2105, U2100, C0895, U1017, U1024, U2106, U2112, U0001, U0101."
This is all the info I have. I took the vette out with the service tech and gave him a white nuckle ride, he left his finger prints implanted on the oh s@#$ handle, did a couple of donuts....I could not duplicate the fault. Traction worked, active handling worked...no codes.....I hope it is ok now. The tech spent 7 hours on the vette, they charged me for one hour diagnosis time; my good. Please let me know what the codes mean, they are not listed on the net for the C6 vette.:W

U2105 No comm with ECM, engine control module
U2106 No comm with TCM, transmission control module
U2107 No comm with BCM, body control module
U2108 No comm with EBTCM, electronic brake traction control module
U2112 No comm withe RTD, real time damping
These are all high speed GMLAN codes and are what I expected, the key is WHAT MODULES had them stored.
U2100 is a failure of the communications line. This code wouldnt be seen if the condition is happening, so I believe that they couldnt make it happen.
U0101 is NO COMM for the TCM. My question, is where was THIS code?
You had the U2106 above, which module has this code?? That could be part of the key to diagnosing this.
U1017/1024 are byproducts of the U21xx codes above. The BCM sees the codes above and sets these.
C0895 is very curious, this was set by the F55 control module for having LOW SUPPLY VOLTAGE.
Now, something to be aware of, if your systems are not getting at least 12 volts, all of these can occur.
That being said, what did they offer for a resolution?
I will be doing further research and post back.
Allthebest, c4c5

 

[Best Vette Yet]

Paul,
I do not think that there was a resolution. The tech tightened up a couple of grounds, I took it for a test drive, everything responded correctly with no codes. This problem may reoccur if I read your post correctly. I will call the dealership and see if they have a record of modules like I requested before diagnosis. I appreciate your assistance.
Michael.

 

[c4c5specialist]

HI there,
Another option, could be havig your dealership to install a vehicle data recorder.
There are 2, either for the CAN line or the class 2.
Personally, I would suggest installing the Class 2, because if the CAN line drops out, this defeats the purpose.
This may be something to suggest if it comes back.
Allthebest, c4c5

 

[Best Vette Yet]

HI there,
Another option, could be havig your dealership to install a vehicle data recorder.
There are 2, either for the CAN line or the class 2.
Personally, I would suggest installing the Class 2, because if the CAN line drops out, this defeats the purpose.
This may be something to suggest if it comes back.
Allthebest, c4c5

Hi Paul,
It may be time for an update.
I have driven the vet for a while now and the problems have not returned. I am still unsure if the problems have been addressed or if they will eventually come back to haunt me......the resolution is still not conclusive in my mind and I find it difficult to sustain confidence in my vet. I do love it though and really appreciate the advice and support given to me by the forum. Great work and thumbs up to all of you who participated in my quest.
Sincerely,
Michael.