Zeus993

I know a I guy (who knows a guy) who lurks here but rarely posts so this is a post for him.

Just picked up a stunning 08 TT triple black cab with nice carbon fiber accoutrements and found the battery dead after a brief period of inactivety. Tried to charge it with the Porsche trickle charger through the cig ligther socket to no avail. Replaced the battery with an after market brand and the car started etc...

Since then the cigarette light is dead and a series of codes and electronics have shut down starting with check engine, then the TPMs, then the PASM shut off, then the PSM.

We ran it into the local dealership here, they played with it for a day, kept it over night to reset the codes or something and all looks good except the TPMs hadn't come back.

Then yesterday after a good romp up into the Cascasdes the engine light comes on again and the cig lighter is dead. No sign of the TPMs yet.

Any thoughts anyone?

LexVan

Bad ignition switch? My only guess.

LexVan

Maybe the prior owner re-wired the cigarette lighter to be a switch source of power and now something is messed up. Shouldn't that be hot/active at all times?

Igooz

When you crank or try and crank the engine on a low battery the DME tends to turn on the fault lamps as you have mentioned. I cannot be precise but for me they were TPMS, PASM, check engine, etc...But after you replace with a new battery and re-start the car, the codes go away, specially, after you drive the car just a little bit so that the DME can get a little time to "figure out" what is going on...

From my experience, the TPMS is the last fault to go away, as it requires the car to get a few miles/speed before it "understands" if everything is OK or NOK.

I don't know about the cigarette lighter. BUT, check your fuse box and make sure that you did not blow out any fuses while changing out the battery...When changing out batteries you need to be careful and take the ground off first and put the ground on last, etc...not make any sparks, etc...

If you bought a lead-acid battery make sure that you hook up the drain tube...

Also, keep your "new" battery on the trickle charger for a couple of days...New batteries maybe new physically, but they may not be at 100% State of Charge (SOC), or they have sat on a shelf for a couple of years...

atcbi5

Seems like a short is being detected, and the CAN BUS system is disabling that part off the circuit. The dealer used the PIWIS to reset it(codes) then it has obviously occurred again. I had something similar happen to me but with the interior door light. My Turbo lit stainless entry guard was bad. Causing an open ckt, high impedance to the CAN BUS signal. Fixed the left entry gaurd (500.00) and took care of it. Dealer wanted $1299.00 to do it.

atcbi5

The termination is used to match impedance of a node to the impedance of the transmission line being used. When impedance is mismatched, the transmitted signal is not completely absorbed by the load and a portion is reflected back into the transmission line. If the source, transmission line and load impedance are equal these reflections are eliminated. This test measures the series resistance of the CAN data pair conductors and the attached terminating resistors. There is a module that probably controls all those common areas you are describing. I believe it's called the "Komfort" gateway if my memory serves me. They read a new replacement into your car. The modules are not expensive the coding is. Take it to the dealer man.

Zeus993

Yes - I agree. Back to the dealer. Tx.

atcbi5

This is what I was talking about.

Igooz

Wow !!! How many micro-controllers and electronic control modules does it take to power the cigarette lighter? !!!

Was the 996 platform also this complicated?

atcbi5

At least one of them :-). Thats what sucks about these cars, if a module fails you have to go to the dealer. If you find what is causing the problem, like a short or cut wire from a bad install, your good. Modules rarely go out on these cars I have been told. It's when you cut wires or tap into them for external power to a device. Any draw of additional current or voltage diff from its intended use....pops a code and might shutdown that system down. That's what happend in my case with the lit entry gaurds. The step up transformer used to turn on the Turbo things fried. The system saw an open load and shuts that job down. Its very evident when some on this forum started replacing the tail lamps with aftermarket LED ones. If you read any of the posts then you would recall numerous fault codes. They had to install a resistor in series to trick the system in thinking all is good. You F**&* with these cars and they will tell you quickly. Thats why me no touchy anything or modify jack! Good luck and let us know what happened.