After some work on my 2007 convertible, I reconnected the negative terminal on the battery. It started up just fine but as soon as I moved a few inches, the car flashed warnings to service everything on the DIC, cluster lights flashed, and the car died. Disconnected and charged the battery and once again reconnected it and tried again. Moved alittle further that time but once again DIC flashed every warning it could and the car slowly died out. Jump to now, nothing major has changed other then checking fuses and swapping to a new battery.

Now the car does the following:
The key fob has no functionality.
Door panel switches (windows, locks, mirrors) do not work.
Soft top will not close.
Car WILL NOT go into accessory mode
Car WILL NOT go into ignition on
Car WILL NOT start or even crank.
Door release buttons (inside and out) do not work.
No lights on dashboard (CEL, Security, Hand brake)
Key fob not detected in little slot in the glove box.

However, the headlights, horn, trunk and fuel door release do work.

When pressing the ignition, there are relay clicks in the front fuse box and the 'dash' makes the normal clicking sound as its trying to detect a fob. It also sounds like the fuel pump kicks on (however I am not certain of this.) There are no blown fuses, a new battery, key fob worked a couple hours before (used to pull into my garage) and scanner can not read from the car as it will not go into acc mode.
I have not found this exact issue anywhere else. Hopefully that is enough information to get pointed into the correct direction. Any thoughts, solutions, or comments are appreciated.

 

Load test present battery.
Betting its given-up the ghost.

 

The first thing with these cars is system voltage. check the battery voltage , full charge should be 12.6 . If not , disconect the negetive cable and charge the battery. There is a good chance the the problems are gone on restart with correct voltage. On restart look what the dash is showing for voltage, should be inthe area of 14 volts. If not you may have charging problem as well. On older cars if the car started you could assume the battery was good enough but because these cars are so voltage sensiitive that is not the case.

 

I have already tried a new battery and now both key fobs (#1 and #2) still nothing from the car whatsoever. Stuck in park, can’t get into acc mode or engine crank. Neither fob will lock or unlock doors

 

Bad battery's usually the culprit, symptoms as described to a 'T'.
OTOH diving deeper, couple other items may be at fault also.

First, check starter connections at solenoid.
Should connecting line(s) become brittle --due to heat cycles and/or age-- they can break, creating an open.
Second, been reported screws holding fuse box layers together work loose over time.
Open under-hood fuse box, tighten screws.

Must start w/ known reported issues/solutions.
It's a process of elimination w/ bad battery being most reported..

 

Both batteries were good, checked fuses and fuse box multiple times. Starter was a non issue, has never given me issues and worked two minutes before the car completely died.
I searched for countless hours online and have only found a handful of people with somewhat similar issues that usually ended up with no answers or solutions on the thread.

A day or two ago I did find the issue, and turned out be to be a module communicating on the Class 2 Data line (and possibly partly GMLAN line). As all symptoms (with various troubleshooting) pointed to BCM and/or RCDLR it was a breath of fresh air to find the culprit. Waiting on shipping, and then getting everything back together before i fully call this a solution. If so, I am going to do more of a write-up edit on this forum post for anyone who may get this in the future.

 

JOgoreck, I'm stuck at work now with almost identical issues you had. I've tried all the things I could think of (swapping fuses, checking the battery, even jump starting from another vehicle, put die-electric grease in all three of the main communication connectors, put a new battery in the FOB, put the FOB in the glove box slot) and it still only lightly "clicks" when I press the start button.

No dash indicators, no door indicators, doors will not unlock, but the trunk and gas cap buttons work.

Also, no car alarm sounded when I used my key to open the hatch, which I then pulled the cable to open the driver's door.

Mine is a 2011 GS with MN6 and and the LT2 package. I'll start a new thread once I find out what my issue it. I'm going to PM Dana523 to find out what Tech 2 clone I should buy too, because I intend to keep the car for a while.

 

Im still testing and working on the write up for this forum post - if you are still having issues shoot me a message and i’d be glad to help! Figured out alot from that stressful week and maybe i can help point you in the right direction

 

This sounds an awful lot like bad grounds somewhere. Any weak grounds resulting in a ground loop will confuse the computers and prevent them from talking to each other reliably.

 

In my case it wasn’t computers not talking ‘reliably’, it was not talking at all. In his case it very well could be bad ground somewhere on the car but sounds awfully close to what i was going through. From the top of my head it was mainly a fault on the Class 2 data line, could have been the GM lane but it’s been a minute. These connect all the systems to the BCM. It technically was a ground on the line (as you said), horn, trunk and gas cap release all still worked , but absolutely nothing else. Basically yes, it’s a ground, however just saying a ground is not very specific and was part of the issue I had when troubleshooting

Just waiting for his reply atp

 

Did you ever get to bottom of this issue got same prob over here in UK no cooms to bcm tcm ecm ebcm etc can get acc mode but no full ign on pressing start button but if you press start with brake applied dash goes black then comes back on with full sweep of gauges (fuel gauge doesn't register ) but still no coms with any modules ? Can run diagnostics if I go in on just vehicle but it won't auto read vin picks up door module dash etc but says all bcm ecm tcm are not equipped??? Got a lot of serial 2 and comms fault showing on dash

 

Do you have an aftermarket radio installed or anything aftermarket along any of those (GM Lane or Data Lines etc etc)?

My issue ended up being a module that connected my aftermarket head unit to the car (Crux CS-GMC2 Wiring Interface) to allow for steering wheel controls and chimes to work. Got a faulty box from CrutchField, it worked for a while with no signs of an issue until it eventually ended up frying itself and faulting the loop (happened after I reconnected the battery.) Took me a LONG time to troubleshoot and find the issue, but finally found it from a burnt electronic smell when getting up close to that module
In my case, they warrantied, I swapped the new one in, and everything worked like a charm with thankfully no other damage.

 

Comm issues are VERY difficult if not impossible for 99.99% of Techs whether independent or dealerships to diagnose...what kind of electrical diagnostic experience do you have ??...you need to check resistance and voltage at pins 6 and 14 and also on the low speed serial data bus on pin 2 of the DLC.

 

A fair bit of general fault finding on electrical systems on cars ! Actually got most of the modules on the hi speed can now disconnected ! Continuity tested the wires according to the gm wiring diagram and all pin out ok so no breaks on the can +/- 1st module back from Dianostic plug is the vcim in trunk and i can see that on the diagnostic machine but nothing else ! Can see doors dash cluster etc on the class 2 strange thing is when I press the start button (no brake) nothing happens no lights etc press acc side and that comes on stereo lights up etc then go to start I get the brake prompt so press brake and start dash goes black then comes back to life few secs later with full gauge sweep and full ign power I don't get any flashing security symbol to say key is searching but can hear the rcdlr clicking away once full ign is up I have had car started and running fine but only by jumping across the starter solenoid relay pins . Only thing so far I found is no ign power being sent to pin 14 of ecm hopefully will do a bit more digging Monday now ! Not so easy over here in the UK parts not so readily available and not many people to do programing . I do have another 2005 c6 in the workshop but pretty sure swapping parts just to check is not that straight forward as everything these days needs to be vin coded Grrrrrrr

 

So do you know how to exactly check pins 6 and 14 and also pin 2 as in the resistance and voltages that should be seen on those 3 ??...for the car to start the BCM, ECM and RCDLR must all be communicating with each other.

 

Sorry been busy with other things double checked the corvette yes getting 61.3 ohms across pins but here's the wierd bit initially seeing 2.5 and 2.3v when acc 1st turned on but then after 15 sec or so can hi lofts to3.57v and can low drops to 1 57v and sits there constantly does change if I disconnected the vcim ecm transmission control or abs

 

First we don't even know what model year or transmission type...Seeing 60 ohms means the "physical layer" is intact which means the wiring into, through, and out of each module is OK...maybe CAN wire is shorted to power somewhere or a bad module...you would need to disconnect a module one by one and jumper the CAN wires that go into and out of that module.

 

OK update its auto trans no suspension module got a ign output fault from bcm so that will need sorting but can liven up the system by back feeding a fuse on the circuit. Next issue is the can with only bcm and vcim connected then the bcm finally communicates then if I add tcm on its 7 × out of 10 crashes the system ? If it don't then I can add the abs mod back and then only occasionally the ecm again mostly crashes it all only managed to get all modules reading once and car started and ran fine but on switching off and back on all comms failed again I will try jumper pins on the tcm module tomoz now as it's nearly 10pm here now and will get back to you all cheers for your help so far . Ps clearly the bcm has been apart before as its had the fixing bolts for the plugs drilled out .

 

Was the BCM output fault a DTC or something else and what did you see ??...someone I helped a while back had his car that would not start and had no comm to TCM and every module downstream of it...was a broken CAN wire on the TCM 16 pin connector...with no comm to ECM the car won't start.

 

No bcm fault is physical looks like a circuit/chip issue hopefully straight forward enough to fix fingers crossed bit more investigation today on which module is actually chasing the system just seems a bit random at mo between tcm and ecm no breaks on loom between blue multiplug near battery to the tcm pins out fine as does ohms on system saying no breaks but just feel like it's an internal fault in a module 100% with just bcm and vcim attached I can see them on diagnostics it's just the last 3 modules that I need to narrow down now