tony51

Here goes: my car has been out of commission for a couple weeks due to an air suspension problem ..the car was totally fine besides the air suspension problem a couple weeks ago I got the car back from a Foreign auto garage that wanted to charge me an outrageous amount for a compressor (whitch im inclined to believe w asnt the actual problem as a result from info I recieved on this forum!!
so I had the car towed back to my house.
I'm going to do the work myself on the air ride system..But that's besides the point right now!The car won't start. no crank no start..
The car started totally fine ever since this whole problem with the suspension..all besides two weeks ago I went to start the car,,it started up totally fine and then bogged out 2 seconds later tried it again started up just fine bugged out 2 seconds later etc etc.. I unhooked the battery the next day for about 10 minutes as i hoped it would clear the system and start back up and I had no luck I disconnected the battery again I looked up a few fuses,actually two fuses for the air ride system and mass level sensor ( which I believe controls the airbag on the passenger seat..inserted them back in.. then went to start the car and it wouldn't start at all!!!
..the headlights come on the trunk light came on the stereo came on the heat came on but usually it wouldn't unless I had it set to come on during start but I never do, the air suspension pump came on which is unusual because it was wasn't coming on recently for more than 2-3 sec each time I started the car..actually it was fine the time I have this air suspension problem ,then a code; That atared "compressor shut down due to overheating...
but now I'm not worried about that this is a new problem!!
As i stated I believe the battery got chewed up during this whole process and it was so low that it caused the 4 codes that came up
: lost communication with TCM
: lost communication with the instrument cluster .unable to read function to the ECU ..
Now the MMI screen finally popped up AND NEVER WENT Done..this was only after my buddy ran scans 5-7 days ago...
So no instrument cluster the car won't start it won't crank headlights come on fans come on the compressor comes on the trunks lit up but the battery was reading that it was dead.. I got it recharged all the way up to full and still is doing the same thing ..
Bought a new battery put it in and it's the same no start no crank the codes are..p0600 diagnostic code points to malfunction of the ECU ...u0155 lost communication with the instrument cluster ..u0101 communication with the TCM
Any thoughts are greatly appreciated
*** and wiring diagrams for the Ecm so I can check the wiring harness the module fuses etc..and or the location of the Ecu/ecm?? 2004 Audi a8l 4.2 Quattro

Jack88

Did anyone try to jumpstart the car? Done improperly, that can damage a number of things. Also, check fuses!

tony51

No we never jumped started it ..but I disconnected the battery for ten min. and hooked the ground wire first and then positive.by mistake..there w asnt any big jolt just the normal little electric static same as when I would hook the ground,as I normally know to do,,it was my only step that i took well maybe mistake ..right before this problem occurred..so either that's the culprit or the low voltage due to my air suspension system being down as I was just about to finish up,so now that's on hold until I figure this out.The car started just fine prior to this ..
I purchased a new battery even though the original was reading full capacity after I charged it and brought it to get tested..I purchased a new one anyway just incase..
All the fuses were checked several times just to make sure..now I'm guessing I have to locate the ECU wiring/ harness/module..check all ..
Or maybe the car need rebooted. I'm running out of options with limited mechanical skills. I have a friend on the way over who is a certified mechanic,but not and Audi technician ..
Any suggestions to pass along to him is greatly appreciated!! Thanks

dvs_dave

tony51

ran scan immobilizer

It's reading that the immobilizer is on

ltooz_a6_a8_q7

Can you take the picture of the battery in the bay with all cables connected? And the voltage ?

tony51

ltooz_a6_a8_q7

Looks good, how old is the scan? What's the voltage across the terminals and the ground pole? Do you have a DVM?
Cheers,
Louis

Giovanni Giovino 6.0+6.0TT

Did you check the fuses under the flap?

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Giovanni Giovino 6.0+6.0TT

Yes it is showing IMMO on, did you try a second key, are you using push button start or key in slot ?
How is terminal # 15 relay, see link starting around post #52.
https://www.audiworld.com/forums/a8-...-work-2905353/