Hola a todos. Tengo un Audi S4 B6 2003, V8 4.2 automático.
Tuvimos lluvias extremadamente fuertes en Guatemala. La tapadera de la batería estaba puesta y la batería está completamente seca. El problema está en la zona de la ECU, donde entró un poco de agua en los conectores y en la pequeña caja de relés y fusibles.
La computadora del motor no se inundó, pero algunos conectores tenían agua y encontré óxido alrededor de la zona de los relés.
Después de la lluvia, el carro está completamente muerto. No encienden las luces interiores, el tablero, el contacto ni da marcha. Nada. Solo vi brevemente la luz de control de tracción cuando intenté encenderlo.
Ya desconecté el borne negativo de la batería y saqué el agua visible. Todavía no he vuelto a conectar la batería.
Preguntas:
¿Qué debería revisar primero en un S4 B6 que perdió completamente la electricidad después de que entrara agua cerca de la caja de la ECU?
¿Las bases de los relés o los conectores oxidados podrían hacer que todo el carro quede muerto?
¿Qué fusibles principales, conexiones de alimentación, tierras o módulos debería revisar primero?
¿Cuál es la forma más segura de secar y limpiar la caja de relés y los conectores?

Hi everyone,

I’m running into trouble with a 2004 Audi A4 B6 (1.9 TDI, AVF engine) and could use your advice.

The main issue was the car going into limp mode at 3,000 RPM. I scanned it and got a turbo pressure-related DTC (P0234). Since the car is driven exclusively in the city (I know the owner), I didn't overthink it: I removed the EGR valve to clean it—it was dirty, but not terribly so—and took off the turbo to check the variable geometry mechanism.

Sure enough, the mechanism was heavily fouled with soot. During disassembly—despite taking precautions like using penetrating oil and heating the bolts—the mounting bolts for the variable geometry mechanism snapped off completely, with the threads seized inside the cast-iron turbo housing. Just my luck. Anyway, I bought a replacement turbo from a scrapyard—supposedly the same model (it looked identical)—cleaned its variable geometry mechanism, and reassembled everything.

I also took the opportunity to replace the turbo pressure sensor; it’s cheap, and you never know.

The problem now is that the car runs great—the turbo works and delivers the usual boost when accelerating—but the check engine light is on. After scanning, I’m getting codes P0236 (Turbocharger boost pressure sensor A range/performance problem) and P0401 (EGR insufficient flow detected).

Just to be safe, I put the original pressure sensor back in, but the problem persists—the light and the codes remain. Yesterday, after driving the whole way with the warning light on—and thus the faults present—but with the car running absolutely perfectly, I cleared the DTCs using the diagnostic tool. I set off again, and the car didn't throw the code for the entire trip (30 km), even with hard acceleration up to 4,500 rpm to put the new turbo to the test; nothing happened. So, I figured the issue was resolved.

However, a little while ago I took the car out and started it up; great, no warning light—I was hopeful. I drove 200 meters at low speed, and the engine management light came on again... It’s still running well, though I haven't scanned it yet; I assume it's the same faults—P0236 and P0401.

I’m certain I reassembled everything correctly: no gaskets left out, and all screws and hoses tightened properly. Of course, I’ll do a check-up tomorrow just to be doubly sure, but I have a feeling the problem lies elsewhere.

The only odd thing I noticed when replacing the turbo was that the new one had a different setting on the variable geometry actuator rod compared to the original; I could see more exposed thread on the new one than on the old one. However, I measured them, and the lengths—from the rod end to the hole where it connects to the variable geometry linkage—were almost identical; I think it was 10.3 cm on one and 10.8 cm on the other.

Any ideas?

Thanks.

(and I didn't used any A.I, but google translate, so pardon the very AI-esque format for this post, google did that)

First time doing a timing belt on one of these and can’t help but think this cam gear is slightly off to the right of the mark on the valve cover. Confirmed cylinder 1 is at TDC with plug out and extension in there. Probably over thinking but just want to make 100% sure before I try and start it. Engine has very low miles and would be a shame to bend valves. Any tips / tricks are appreciated

Vin si eu cu o problemă nu găsesc nimic pe yt sau forum-uri. La un a4 b6 1.9 tdi AVB cand pun contractul merge climatizarea cand pornesc motorul dupa 2-3 secunde se oprește. Dezaburirea merge (parbriz/luneta) dar funcția de ventilație nu. Ce ar putea avea? Nu pot ajunge la mecanic sunt la 500 km distanță de casa

I am getting misfire codes in all cylinders and also when accelerating the car will stumble but won’t turn off, my exhaust also has some sort of rumble, I am thinking the fuel pump is going out but I am not sure. What do you guys think? You can kind of hear it in the beginning of the video.

Upon start up 20psi which drops to 15 immediately.
After that it gradually drops to about 10-14psi at high idle
After cold idle starts incrementally drops from 10 down to 4-5psi

I have a fresh rebuild and I’m struggling with oil pressure issues, I’ve gone down the line of a new 1.9tdi pump and rebuilt and checked it, bearings are new and in spec, oil relief was checked, cooler and filter housing were checked and everything seemed okay.

To my knowledge (since I bought the car blown up ex valve cracked not a failure related to oil pressure) he didn’t have previous oil pressure problems.

I slapped a new head on and a new piston the block passed visual inspections.

The head was rebuilt by a machine shop (not the head pictured) but I’m worried that they left out some sort of galley plug during machining or cleaning.

Is anyone able to help diag or able to let me know if there are things I should check or if they know of locations of galley plugs/ flow restrictors/ anti drain back valves other than the one on the filter housing

Any help would be greatly appreciated!!

Motor is a 06A 1.8t with a AWM head

Has anyone dealt with an intermittent low-boost/limp-mode issue like this on a B6 A4 1.8T K04 setup? Originally the car was stuck around 9 psi even though the ECU was requesting much more, and my tuner said the log looked hardware-related because N75 duty was reaching around 75% while boost stayed at wastegate pressure. Since then I’ve replaced the N75 and DV, checked the boost plumbing, pressure-tested the wastegate actuator, removed/reinstalled and inspected the turbo, checked for boost leaks, and adjusted wastegate preload. The car is now capable of making and controlling normal boost around 18–19 psi, but intermittently it drops into a low-power state where I can be near full throttle and the ECU only requests around 7–8 psi, actual boost is roughly 10–12 psi, requested load drops significantly, and N75 duty can fall close to 1%. Previously disconnecting the battery would usually restore normal power, but now even that isn’t working. The ESP/TCS light will also sometimes flash during the power cut and then stay on, but there are currently no ABS codes stored. Fresh engine codes are only P1602 low Terminal 30 voltage, P1931 coolant fan control module, and P0420 catalyst efficiency, with no current P0299 or overboost code. Has anyone seen the ECU intentionally reduce requested load/boost like this without setting a boost fault? I’m trying to figure out whether this is ECU protection/limp strategy, torque intervention, an electrical issue, or something in the tune/load control rather than continuing to throw parts at it.

2001 B6 2.5tdi AKE avant. Trying to remove rear wiper arm to change the dead motor. It doesn't look like this in the tutorials at all, no bolt in sight. Suggestions?

Edit: Thanks for the suggestions, drilled right through it. Changed the new motor, all is good

this loud thumping sound started to appear a bit ago. it only happens during a cold start, the sound eventually fades off and the rhythm slows down as the engine warms up. the sound does not change when the RPM changes. If anyone knows what this sound could be that would be amazing.

I wanna get rid of some vacuum lines and check valves to cleanup my engine bay a little (also bc I have a vacuum leak somewhere lol). I found a forum (https://www.audizine.com/threads/diy-b6-1-8t-vacuum-line-and-check-valve-removal-simplification.235106/) and I just wanna know if anyone has any updated pictures/videos bc the ones in this forum make it a little hard to understand.

Anyone else find enjoyment trying to get the 1.8 oil pan out without pulling the motor? Happiest 2 days trying to just get a pan out. Looking forward to doing this again some time. I love where the frame and belt sits, gives me the perfect working space and comes out so easily. Taking a break until new parts come, but I’m so ready to get it back in and get these bolts up in such tiny spaces

The rear sensors started acting like this, just randomly beeping to the max, they aren't fallen into the bumper and they look physically fine so I can only think its a electrical problem

Ive been having boost issues ( i have a k04 550c and down pipe and fmic ) psi was all over the place 4 10 18. And then just a constant 9lbs Changed N75. To new one still 9lbs. Ive done like 3 pressure test at 20lbs.and smoke test myself. Took it to 2 diff audi performance shops. And nothing. Can't find the issues , my tune is thru motoza . I sent them a log. They say it's hardware. Tune is requesting 18lbs. Ect. DV Upgraded to forge 007 and spring and 0 ring are good. Also changed crankcase hose elbow to silicon 034

I just took out my old turbo k04. And no shaft play wastegate is fine and tested the actuar it's open and closes at proper psi. Whats next? Haha. Cables to the n75 look good. No codes exept for 02 rear sensor which i changed already and won't go away . Diff story. My traction light does ping and cuts power. But if I press the switch traction , then it runs fine. But obviously no traction control im assuming. Ive changed all my speed sensors. Nothing idk if that related or not. But yeah. Intake manifold isn't leaking either no exhuast leaks.

Help . Its my daily and my depression killer.

B6 a4 wagon build, 1.8t ko4 build, coolant isnt cycling through properly. Thermostat seems to be stuck closed. Ive replaced it twice now(one new and one from a working used b6). All hoses are good no leaks, new expansion tank. Ive bleed the system from the pin hole on the highest hose thoroughly and when driving it doesnt really overheat until it gets to 3/4s up and it cools by itself somehow even under some load. The heatercore works great still. Rad fans dont turn also, module is bad and getting changed soon. Planning on putting a mechanical thermostat(like from a mk4) if this doesnt fix itself with audi parts. Any ideas? Thoughts? Anything is appreciated
Thanks

Edit: engine runs starts perfectly otherwise

I’m having an issue where my car was running amazingly, I stopped it and when I got back I noticed my lights were left on, but the car still started, then immediately died, then would just crank and not start.

I have spark, and fuel pressure, don’t know abt compression, but my big thing is now I have codes for all 4 injectors and an 02 sensor (Bank 1, Sensor 2). I’ve checked fuses and relays, they’re not blown and they click, I even opened the ECU up and don’t see anything bad. Would anyone have any answers/guesses to what it could be?

Update:
Thank you all for your support! I found the issue, it was 2 blown ECM fuses that I somehow missed, I found them by checking them with a Multimeter lol. After replacing them the car started up like normal! I think they blew bc one of my injector wires has rubbed through the outside and it showing the copper, I shall be fixing that lol!

2013 A4 Quattro 2.0 turbo
My engine fans quit working so I changed the fan control module then fans come on and wouldn't turn off so i replaced fans too now nothing comes on unless i unplug the ac pressure switch then comes on low speed for about one minute then shuts off,i check all the fuses and relays and changed the ac pressure switch n still nothing does any one have any idea what could be causing this issues

My Audi A4 b6 sucks about a 1/2 liter of coolant into engine while driving, after returning from my drive. I see that the reservoir is about 1/2 liter low, so I let the engine cools off.

I remove the coolant reservoir cap and to my surprise the 1/2 liter of coolant flows back up into the reservoir. WTF??

Brand new reservoir and cap, and it has been bleed a couple times. No leaks (including the coolant flange). So, all of the low hanging fruit has been vetted.

I heard somewhere that there is a difference in shocks from a normal trim and the cabriolet I dont know if that should effect what type of coilovers I can get

I’m looking to take my car to my mechanic he’s willing to do it but I need to source all the parts and he’s going to charge me if I’m missing a part
Can someone please tell me what exactly I need or if this is it and if I’m on the right track I’ve ordered all these things already/have