C6 non starter?

stealthyflatfish

stealthyflatfish

Well-known user
Good evening you lovely people, just trying to help a new member out, so please don't shoot the messenger! 2006 C6 I know very little about this model, but know earthing points can be an issue ? Especially after a battery change.
I'll post below his problem.
Keith the problem its having is it wont start press the green start button asks you to put foot on brake , the dash goes dead then it recycles . then i get a shift to park message . was starting fine then battery went flat overnight and i noticed when i put new battery on the acc button was still lighting up and the radio etc but not the dash lights pulling my hair out.
 
Oneball

Oneball

CCCUK Member
4 thoughts

1 new battery is duff, check it’s voltage
2 the original battery wasn’t faulty and there is an earth/starter/solenoid issue
3 you’ve blown a fuse
4 is there a security reset on the C6? ie lock then unlock then start?
 
stealthyflatfish

stealthyflatfish

Well-known user
Thanks for replying, Oneball
Point 4 as far as I'm aware there is nothing to reset on a C6 after a battery change, other than the windows. As stated it's not my Vette so can't check the other points. But assuming? the battery is ok, I'm leaning towards a bad earth.
 
teamzr1

teamzr1

Supporting vendor
Ask owner these questions

1. Is it totally stock ?
2. Any other repairs done recently ?
3. Did they replace with a brand-new battery ?
4. Did they check this battery as the right one as to cranking amps, etc ?
5. Have a OBD-II scanner or error code reader, with just key on, what are the error codes ? (DTC) that would tell me where to go looking.
6. Which C6 year/Model ?
7. With a volt meter, measure at battery posts, what is the voltage reading ?
8. Now go to the fuse panel in engine bay, there is a positive connection from battery, at corner outside of fuse panel
Measure voltage from that point and ground, what is that voltage reading ? Check ground right below that as clean/tight
9. With just key on, engine off, does the radio, windows, etc work ?
10. Voltage reading at the cigarette lighter ?

11. Possible the owner when swapping battery put the battery leads onto the wrong polarity posts of battery
as if so could have blown the fuse links which have to find and see if they are not shorted out
12. Check main fuses for the PCM, BCM, IPC (dash) controllers, they will not work if voltage is less than 12.5 Vdc
13. May have to check voltages and ground at starter

Remember the BCM (Body Chassis Module) is the boss, as all controllers connect to the CAN/GMLAN networks and talk to
each other via BCM, so if it is not getting power or ground then all controllers are deaf and cannot function and share information

Engine bay Fuse panel

C6-EBfP.jpg
BCM, Fuse Panel, Relays. On-board CAN/GMLAN Networks

C6BCM.jpg
 
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P

phoneguru

Regular user
yes brand new battery 2007 stock c6 auto no other work done windows doors etc etc work with fob present . on locking car radio remains live thus running battery down acc flashes on with car doors locked , it seems car is not shutting down . the accessory light won't turn off. I close the car door and the car beeps 3 times. It is running my battery down. no chance of positive negative ever put wrong way round . what fuses may i need to check , car was starting till went flat . put another battery on started fine but radio etc still stopped on . getting on dash shift to park ! now car wont start
 
teamzr1

teamzr1

Supporting vendor
phoneguru said:
yes brand new battery 2007 stock c6 auto no other work done windows doors etc etc work with fob present . on locking car radio remains live thus running battery down acc flashes on with car doors locked , it seems car is not shutting down . the accessory light won't turn off. I close the car door and the car beeps 3 times. It is running my battery down. no chance of positive negative ever put wrong way round . what fuses may i need to check , car was starting till went flat . put another battery on started fine but radio etc still stopped on . getting on dash shift to park ! now car wont start
Click to expand...

Did the problems get better or worse when a new battery was installed ?
If worse than another new problem was added, and I would suggest the battery be load tested as even new could have bad cell(s)
and assure the ground cable is OK, so someone has to go through the punch list I posted and weed down the problem and second high on that list is check for what error codes tripped and what were they
If I recall correctly C6s had a problem and GM put out a TSB as the battery cables was a flaw in the terminal connector of cables to battery posts
were defective, as bad crimps of connectors to end of cables and needed to be replaced and why in my list I say to test voltage at the main point of the fuse panel next to battery and must be around 13 volts

To help I have attached the whole wiring drawings from GM that can be used to track down how all is connected

2 things about radio for C6,

1. when ign key is just turned off it is built as a feature, but some things like the radio will stay on for 15 minutes and then turn off, so you have to
see if that happens
2. Within that 15 minutes and a door is then opened, the systems are shut down
IF both of those do NOT turn radio off then some controller is not telling the radio control to shut down

GET those errors codes and post them to narrow in what the problems are.
 

Attachments

  • 2006 WIRING.pdf
    4.6 MB · Views: 1
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phoneguru

Regular user
just put obd code reader on no error codes , obd reader communicated fine shows vin etc etc etc but no error codes . yes it seemed to get worse ie not starting when i put new battery on , so put another fully charged on this morning same symptoms with shift to park showing . and when trying to start press foot on nrake comes up then try to start dash goes dead then shift to park shows
 
Oneball

Oneball

CCCUK Member
If it was just one error message eg “shift to park” I’d say sensor but because of all the other stuff I’m still going to earth.

Do you have a multimeter so you can check voltages and resistance. Would be good to measure resistance between the battery earth terminal and another earth point on the engine.

Can you get it out of park with ignition on and foot on the brake and do the brake lights work? That’ll go someway to ruling out sensors as an issue.

If earths are ok and sensors don’t seem an issue my next thing to look at would be starter motor/solenoid.
 
Oneball

Oneball

CCCUK Member
Sorry didn’t read your first post.

My guess is and this is a guess is that it doesn’t think it’s in park

other guess are you might have an ignition switch problem or a sticking power relay.

What happens when you switch it to acc and then off?

I’ve never driven an auto C6 does it show you what gear it’s in?
 
teamzr1

teamzr1

Supporting vendor
phoneguru said:
just put obd code reader on no error codes , obd reader communicated fine shows vin etc etc etc but no error codes . yes it seemed to get worse ie not starting when i put new battery on , so put another fully charged on this morning same symptoms with shift to park showing . and when trying to start press foot on nrake comes up then try to start dash goes dead then shift to park shows
Click to expand...

So that says the problem is not being seen by any of the controllers or sensors
This would be a lot easier if you used a OBD-II scanner and looked at the parameter for the park switch and see if in fact reports that switched open or closed
Also, when door is open, does the security light in dash flash, as if hard on that would say the BCM is not talking to the PCM so for security would prevent starting engine

Follow this drawing I attached here starting with the fuse I point to and then follow the grounds, brake and park switches
Also need to assure the fuse for the BCM is not blown

Might be easier if you print this photo, so it fills the printer paper to see better as this is all that is involved for starting

Look at the 2 fuses and the arrows I point to

tranny2.jpg
 
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stealthyflatfish

stealthyflatfish

Well-known user
Well done all, and especially team zr1 for posting the diagrams, an excellent result for the member and information we can all refer to in the future 👍
 
Custom exotics

Custom exotics

Well-known user
As this is an auto have u checked it is fully engaged into park and the gear stick lock button is full in its out position had a c6 do this with us and it was the press in gear release button sticking so car wouldn't recognise it was locked in park
 
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