3dmatters2us

Hello Everyone: Its official, I made it to 134K miles before my first transmission issue on my 2000 A8 (picked up the car with 123K on it). I'm getting constant P1819 and P1824 error codes (yes, transmission solenoid errors). This has never happened before with this car. The codes will not clear...even when I clear them with my OBD tool. They come right back within a few seconds. I don't even have to start the car. Car is locked in limp home mode. My research tells me the TCM went bad. Battery is at 12.5V at rest and 13.5V running. Pulling the battery did not make them go away either. I don't have the fancy manual and VDAC yet (excuse me for mis-labeling...still a noob with this car). Any thoughts about this situation please? Thank you!

FYI: I have not taken to an indie shop yet as I just had it towed home a few hours ago. I'd like to keep my $$$ in my pocket before having it towed to a shop. Feel I can fix this IF I can get more information first from other enthusiasts. Thank you!

adeneo

Before you swap out the TCM, start by checking the connectors between the transmission and wiring harness, both of them, but specifically the one to the valve block, then get VCDS and check the measuring blocks to see what's really happening.

The open the box under the hood where the TCM is, right side all the way up by the windshield, and see if's wet.

3dmatters2us

Thanks for the quick reply! I will try that. Last night, just for the sake of trying, I put a battery charger on it all night. This morning, I cleared the codes and started it again. I was able to get P1819 and P1824 to clear, but now have P0304 (cylinder #4 misfire). Its been idling rough since this started yesterday at a stoplight. I thought it was part of the limp-home mode, but now I'm not sure. It was idling this morning without limp-home mode, but CEL illuminated. With deceivingly unrelated things like this, I'm going to pick up a new battery this afternoon and see if that solves anything (since charging the battery all night allowed me to clear P1819 and P1824). I'll let everyone know what happens.

3dmatters2us

Update: New $150 battery did not solve the problem (ouch). Idles rough when you start it...still throwing P0304 code for cylinder #4, so I'm changing plugs tonight and checking to make sure I'm getting spark on that cylinder. I'll try swapping the ignition coil with the one next to it. If the problem follows, I'll know exactly whats going on. I'm also crawling under it tonight to check transmission harnesses per adeneo's suggestion. Maybe my wife ran over something and forgot to mention it. She did that with a Volvo I used to have. The branch she ran over pulled the O2 sensor wire out and caused a short circuit in the ECM. Blew a trace line on the ECM main printed circuit board. I was able to fix it, but it was a bear to find.

jfrahm

As suggested is there a chance the TCU got wet? If your central cowl drains are plugged this happens.
See audipages.com for procedures to clear them. You may also get water coming out the rear seat AC vents, but it could also be that the cowl drains but not fast enough to keep the TCU from getting wet enough to act up.

3dmatters2us

I replaced the spark plugs tonight. They look to be original units and were not in great shape. It still was idling rough. I then moved #4 coil pack and swapped it with number 2 coil pack. Cleared codes and started the car. The car was still idling rough. When I checked the codes, I now had P0302! Voila! The problem followed. They are $32 at the local auto parts store. I feel silly now. Sorry to waste everyone's time reading up on such a trivial problem. I still don't know why it keeps throwing the P1819 and P1824 codes too. Maybe it is a byproduct of the limp home mode. We will see after I put the new coil pack in tomorrow.

Just for my own piece of mind, I took the bad coil pack out and set it on top of the manifold (still plugged in). Got out my analog test light and started the car. As I hold the grounded test light near the end of the coil pack, the spark should jump out with each cycle. For this pack it does not. I have to get the tip almost to the spring inside before a spark jumps. I tried the same test on a known good coil. The spark jumps about an inch away from the end of the boot. I learned how to do this on my old Volvo S80. It chewed through three coil packs in a six month time frame. Never the same cylinder. If you try this test, be careful. It still 10-20kV flying out of that coil.

The lesson here is keep an eye out for the simple things before jumping down a rabbit hole. Reading about all the transmission issues others have seen got me thinking this was a bigger problem without going back to basics first: fuel, compression, spark. If you are missing any of those three, you will not have ignition.

3dmatters2us

I replaced the coil pack tonight and she purrs like a lion again. However, the saga continues. I am stuck in transmission lockout mode. I cannot even move the car. P1820, P1825, P1814 (I think the last one is a known problem with the back door). The other two WILL NOT CLEAR and come right back immediately after being cleared. I took the battery off for hours, no luck. I took the TCM connector off and its dry as a bone. I even popped the cover off the TCM and no signs of moisture or obvious damage to the printed circuit board. Cleaned the connectors anyway. No luck. I took the 16 pin connector for the valve bodies off and cleaned both sides with contact cleaner. No luck.

Here is a theory....when the coil pack failed and the car went into limp home mode, could that have done something in the transmission to cause this error codes not to clear? Could the transmission be "stuck?" I cannot tie these two problems together any other way.

I would like to check the valve blocks (without dumping the pan) but I'm not sure how. Any suggestions from "the collective" on next course of action here (except call a tow truck)? If anyone can share the pin-outs and expected readings from the valve block 16 pin connector, I'd buy you a drink! Thank you.

3dmatters2us

Here is the magic question to the group: CAN YOU GET A D2 A8 OUT OF LIMP-HOME-MODE WITHOUT A VAG-CAM DEVICE? All I have is a generic OBD-II scanner. Every time I try to erase the P1820 and P1825 error codes, they come right back. The car is stuck in the limp home mode. I got desperate yesterday and took apart the center console to expose the shifter. I was able to manually disengage the locking solenoid with a small screwdriver. It on the drivers side. You'll need to poke it with the side panel removed. This allowed me to put the car in reverse and get it out of the garage. I then did the same think to put the car in drive. Its stuck in 4th gear. At least I could move it. No, I did not attempt to drive it. Yes, I know it was a risk if there was something seriously wrong with the transmission. IF ANYONE HAS A VAG-CAM SCANNER IN NEW HAMPSHIRE AND IS WILLING TO VISIT WITH IT, I WOULD REALLY APPRECIATE IT. I'd probibly buy you dinner. Hit me up and we can talk off-forum. Please go to my website, 3DMatters2Us and send me an email. THANK YOU!!!

jimmy2222

I know you already went through TCM connectors etc... However, I work at a Subaru dealership, and I installed a brand new remote starter on a brand new crosstrek XV or something the other day, and the box was unopened, looked alright, had everything hooked up properly, double/triple checked, went to program with our 'scantool' // software and it would not register, tried every which way, glanced at connections again, all good, nothing came loose putting panels back...

Pull off connectors/harness and dabbed some 'stabilitant' (75% isopropyl alcohol IIRC) on pins, hooked it back up, good as 'new'

Looks can be deceiving. Can't hurt to give it a go with some sort of cleaner.
BTW, registered just to say this to/for you. Lol....(also looking at picking up a D2 S8 from JDM land - LHD, killer deal).
I was about to replace the module and had another unit busted out and opened until I asked on more of the other techs and he said he did have a similar issue recently, did the exact same thing, a bit of this 'stabilitant' on the pins and voila. I'll tell you exactly what it is tomorrow as long as I can find one of them, lol.... Small little bottles...

Cheers, glad to see this forum is active.

3dmatters2us

OK. I finally got a VAG-COM system to really look at the car closely. This interface really does help a lot. I also downloaded the shop manual. I believe I have a defective TCM. I'd like everyone to take a look at what I have seen to verify my conclusions please.

Address 02: Auto Trans Labels: 01L-927-156.lbl
Control Module Part Number: 4D0 927 156 CP
Component and/or Version:
Software Coding:
Work Shop Code:
VCID: 79ACE57360CC6C8F1C4-5160
3 Faults Found:

18170 - Shift Lock Solenoid (N110)
P1762 - 35-00 - Short to Plus
18233 - Pressure Control Valve 3 (N217)
P1825 - 35-00 - Short to Plus
18227 - Pressure Control Valve 2 (N216)
P1819 - 35-00 - Open or Short to Ground

These codes can be cleared with the VAG-COM, but come right back when you stop and restart the car each time.

- I used the shop manual and my DVM to verify the following:
a) shift interlock solenoid measures 222 ohms. It moves to the lock position when ignition is on. When you press the brake, it will not disengage. If you shut the car off, it disengages. The brake lights and switch works fine.
b) pressure control valves 1-4 all read fine at 6.9 to 7.4 ohms
c) solenoids all read fine at 29 ohms
d) When measuring group 3 in the transmission, "Terminal 15" is at 0V. Its supposed to be 10-16V. I took the TCM apart to verify the B+ is actually appearing on pin 26, 54 and 55 of the TCM. B+ is there...but the TCM is not reading it. I did check all the grounds. They are fine. Battery is new.
e) I tried exercising the TCM through output testing, but it tells me "Error - not available" when I tell it to start. The shop manual said it should be available.
f) I tried to re-code the TCM via the procedure outlined by Ross-Tech. (Go into 02-Auto Trans, Basic Settings-04, Set Group 000, Go!, press the accelerator for 3 seconds, Go back.). When I clicked on "Go!" the values to the right said "Error - not available."
g) I was able to exercise the shifter by bypassing the lock-out solenoid. This allowed me to watch the multifunction range switch in the advanced measuring blocks. It looks like each gear change registered.

I opened up the TCM and looked under a magnifier light looking for signs of open trace lines, blown components. I don't see anything. No evidence of moisture either.

I believe I need a new TCM. If I missed something here and you have a new path to follow, I'd love to hear it. Thanks everyone!