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2013 GTC won’t start after battery charge/replacement
Hey guys, another GTC owner here. Charged battery on sunday and bricked the rig. It spins starter but won’t fire up. If you do hard reset: it may start for 3-5 seconds and dies.
What have been done:
- Checked ECM1/2 and all under hood wiring for corrosion and reseat it all; trunk wiring and BCM wiring under glove box.
- Changed Aux battery with new one, constantly running 12.7v +. Couldn’t program/register the battery (feature not supported?!), but new battery gives exactly same issues.
- Checked fuses. Ground lines.
- Changed relay 53 (since it was the only after market one.
Same symptoms. Same codes. About to give up and need an advice. Would not mind to compensate for professional help.
As to your issue, please give us some detailed information as to the status of the vehicle before this occurred.
Was the vehicle in any collision, or any damage of any kind ?
Have any repairs or replacement of the airbags, airbag module, ABS braking system module, steering column module, or either engine ECU'S taken place ?
Do you have Ross-Tech VCDS instead of the Autel ?
Have you read the fault codes of engine ecu number 2 as per P1923 instruction ?
I take it that P1647 is from engine ecu number 1, if not, where is it from ?
A full scan would be of great help, as other individual modules can cause this P1647 code, a Ross-Tech scan or ODIS VAS 5054 would be great, as they give detailed in depth reading, whereas, I am not so sure with the Autel, if the Autel has a full scan readout, please post it here.
"Was the vehicle in any collision, or any damage of any kind ? Have any repairs or replacement of the airbags, airbag module, ABS braking system module, steering column module, or either engine ECU'S taken place ?]"
I will explain as detailed as possible, please bear with me. Bought the car from used dealer off Seattle. It ran flawlessly there, then after week on a barge it started up flawlessly also. Been using it once in a while when weather is nice (probably 1k miles in 2 months). Never had issues. Noticed that Seat Belt Extender (the arm) didn't work, so I bought Autel (after research, just to have it in my garage, usually was borrowing SnapOn from buddy of mine, but his doesn't support Bentley). Last Sunday I took it for a quick spin, came back home and plugged Autel, scanned whole thing, checked the arm thru Actuator tests (worked fine, now I need to figure our why is not bringing me belt when I sit down, but it is a different topic). After 15-20 minutes dash said that my battery is draining, so instead of driving the car (it was rainy) I brought my charger ($200 dollar one) and plugged it to Main battery, left it for a few hours. I owned handful of BMW and Porsche, did the same thing as a habit. After few hours I wanted to bring the car inside of garage, and it refused to start. Starter spins fine, but it didn't fire up. That's how whole saga has started.
"Do you have Ross-Tech VCDS instead of the Autel ?"
No, but if it's better and Amazon-able, I can order it.
"Have you read the fault codes of engine ecu number 2 as per P1923 instruction ?"
If it's some sorta specific task - then no, But when I read all codes, ECM2 shows same error - implausible signal.
"I take it that P1647 is from engine ecu number 1, if not, where is it from ?"
Yes
"A full scan would be of great help, as other individual modules can cause this P1647 code, a Ross-Tech scan or ODIS VAS 5054 would be great, as they give detailed in depth reading, whereas, I am not so sure with the Autel, if the Autel has a full scan readout, please post it here."
I will go ahead and put the ECMs back into the car. Pulled them out last night to check for connections and corrosions, and do whole module reading and find the way how to import it here.
@ingvarr ,
As to relay 53, that is the suspension compressor relay, so nothing to do with the engine.
The two relays to the right of 53 are the relays for the fuel pumps, I would verify power, and or possibly jump the fat blade sockets on each relay one at a time to verify fuel pumps running, but verify that the fat socket of each relay has power from each fuse.
Please state either W12 or V8 in your GTC.
Did you verify all mega fuses mounted on the house battery, also all fuses at the 4 other locations, being the facia fuse box, the engine compartment fuse box, the fuse box on top of the starter battery (right side), and of course above the house battery left side ?
Which brings me to the question of what type of battery charger did you use, as in what amp setting ?
As to your Autel scanner, I can not help your with that, I use Ross-Tech VCDS and ODIS.
https://store.ross-tech.com/shop/cat/VCDS/
Johnny
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Last edited by Johnny Hotspur GT; Jun 11, 2025 at 02:01 PM.
@ingvarr
As far as Amazon, Ross-Tech is not on there, but.
You can order from RT in PA (link in last post) with 2 day priority shipping to Alaska at an additional 60-70 bucks shipping cost, or you can get the same equipment from their affiliate in Oregon for less shipping cost by ground.
Don't want to sound stupid but I didn't even know about other fuse boxes. Can you be more specific about the ones which are not in the trunk (which I checked, both).
The charger I bought years ago, a Craftsman, fully automatic charger-booster-maintainer. I select charge mode which is 6-12A, it charges then switch to maintain mode.
As of the engine it is W12.
As of pump, you immediately can smell the fumes when it cranks, at first I thought it has something to do with pump until we roll the car into garage and immediately started to smell gasoline after start attempt. Someone mentioned something about immobilizer, I don't know if it might be related. There is no after market security as far as I know. Please let me know where to find other fuse boxes, after I was able to pull ECMs I don't think I will have any complications finding and digging the fuse boxes out.
@ingvarr ,
Ok, you have a W12, and it is a 2013, but it is also a GTC, so things may be a little different, but here is the information that is up to 2011 for GT.
Boot area fuses, the mega fuses under the cover on the house battery left side, the fuse box above the house battery that you know already, the fuse box mounted on top of the starter battery.
Interior dash fuses, the Facia fuse box in the driver's side dash knee pad area.
Engine compartment fuse box, the E-Box under the cowl next to the engine ECU'S, remove the E-Box lid to gain access to fuses and relays.
As to the IMMO comment, I would agree to a point, your 2013 has IMMO 4 iirc, and if you had a KESSY immobilizer issue you should have a warning message in the DIS between the speedometer and tachometer, if you had a KESSY module immobilizer issue, the warning should be immediately displayed, and the dash should not power up to allow the cranking of the engine, whereas, if you have an engine ecu immobilizer issue, then the system would allow the engine to crank and start everytime, but the engine would die in 2-3 seconds, but again, it would fire everytime for those 2-3 seconds.
My video below showing immobilizer kicking in with matching key-fob, KESSY, steering column module, instrument cluster, but with non matched engine ECU'S, as ECU'S are from the Supersports engine transmission package I installed, therefore no warning on dash, and all powers up and starts, but dies in seconds due to engine ecu immobilizer kicking in.
As I think of other issues causing the no start, the (G28) engine speed sensor comes to mind, as that was my first issue upon the installation of the Supersports package, I had fuel, and no immobilizer warning, but it failed to fire over at all, I took out the new one I had installed prior, and installed the broken socket G28, and she fired right over, be it for 2 to 3 seconds as the engine ECU immobilizer kicked in.
Your G28 part number may be different.
EDIT: And now as I look back at my pictures, I see that I had the same "P1647" fault code along with the G28 crankshaft position sensor.
Johnny
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Last edited by Johnny Hotspur GT; Jun 11, 2025 at 05:08 PM.
Reason: Add information and video
As to your issue, please give us some detailed information as to the status of the vehicle before this occurred.
Was the vehicle in any collision, or any damage of any kind ?
Have any repairs or replacement of the airbags, airbag module, ABS braking system module, steering column module, or either engine ECU'S taken place ?
Do you have Ross-Tech VCDS instead of the Autel ?
Have you read the fault codes of engine ecu number 2 as per P1923 instruction ?
I take it that P1647 is from engine ecu number 1, if not, where is it from ?
A full scan would be of great help, as other individual modules can cause this P1647 code, a Ross-Tech scan or ODIS VAS 5054 would be great, as they give detailed in depth reading, whereas, I am not so sure with the Autel, if the Autel has a full scan readout, please post it here.
Johnny
Johnny….How difficult is it to use the VCDS? Where does it get plugged into, etc, etc.
I’m coming out of warranty and would like to do some of the diagnostic myself.
Hello @warrickbl ,
The Ross-Tech VCDS is very easy to use, it is much more user-friendly than the ODIS VAS 5054.
The RT VCDS is a software that is loaded onto a Windows Based laptop, the dongle plugs into the OBD port located at the lower left of the driver's side dash.
Ross-tech also has a mobile version that works with any smart device that has wifi, iPhone, Android, tablet, etc.
I hurt my back right the next day and it took me over a week to get over it. I am in garage tonight, trying to get back on track and figure it all out. Sorry for disappearing for a week.
Here is update. I found all fuse boxes, I asked my mechanic friend to come over and help me - we tested all available relays, fuses, everything is perfect. But here is my observation: I found this module, which got me thinking it might be bad one, Someone somewhere said if I charged my car with my 6-12A charger, I could blow it as it accepts only up to 5A. You might be the one who said it, or someone on facebook. So, I did diasconnect the module and started the car - exactly same behavior - it started and worked for 4-5 seconds, then shut down. I went to Autel and check the Gateway, found this module missing (as well as audio, i haven't plugged it in yet, don't pay attention to it). So, then I plugged the module back in and rescan whole thing, I gor an interesting error 0470:011 (attached) - Combination comfort databus in single wire - open circuit). I have all hope in this module to be bad. F*cking expensive, but I will order one if you think I am right. Also, Idk if is appropriate, but here is my cell, I'd love to chat with you if it's possible / or more convenient. 907-841-7777. I live in Alaska. Thanks! Appreciate all the help.
