masalon

The car won't start at all from the garage, no crank. Dashboard notifies "Fault in ABS brake system" when switching on and flashes red brake warnings.

VCDS tells:
from the engine

• 18034 - Powertrain Data Bus P1626 - 004 - Missing Message from TCU
• (in addition, before erasing errors there was 17887 - Brake Boost Vacuum System P1479 --08 - Mechanical Failure - Intermittent)

from ABS

• same code 18034 and also 18055 - Check Coding of ECUs on Powertrain Data Bus P1647 - 35-00
• (and additionally, 01826 - Sensor for Steering Angle (G85), Supply VoltageTerminal 30 - 35-00)

Battery is charged. The negative terminal of the battery was disconnected during the installation of the new radio. I've also tried removing the cables of the new radio installation and then disconnecting the battery shoe again for a long time (I haven't tried connecting the battery cables together).

While surfing through the Internet, I also came across such a comment, “Any time the battery has been disconnected on an automatic transmission vehicle, it will be necessary to reestablish the Transmission Control Module (TCM) basic settings using the VAG 1551 Scan Tool (ST).“ Does this mean a similar reset, what is done with the doors locked ignition on and gas pedal floored down?



The protective case of the car's ECU was opened and the two relays below it (219 and 369) were DIY-checked to make sure they work as they should (there is a click from the current, and the current flows in the second circuit then) + checked two fuses near the relays.



I guess the TCU is inside the automatic gear box in this model. Tried to make sure the connectors are fastened. Connector behind the gearbox was new to me, didn’t know it should be tight. There was a T-connector in the gearbox cable in the middle of the engine compartment, which you can't see or reach properly, some 20-30 cm away, got a little oily dirt, I couldn't open it.



If the windscreen washer’s fluid gets onto the connector of the ABS unit (during fluid adding), can it do such damage to mess up electrics? The connector didn't seem to open very easily, seems to be stuck.



Is there e.g. Erwin-site where to find the correct wiring & relay diagrams based on the VIN code? So it would be possible to find out if TCU and / or ABS unit go through a relay, or which wire goes where. Somehow, I haven't come across any pictures on the internet that show only two relays that can be found under the ECU and 3 or 4 under the dashboard (167, 53 and 373, and one white without number, probably a relay too). Or can there still be some "hidden" relays somewhere inside the car?



The fuses were checked with the meter on the side of the driver's door + under the dashboard.



What connectors are in a row under the coolant tank? Theoretically, it is possible that someone would have been bumped when I fastened the coolant tank back after installing shock absorbers. (Used the car couple of times after the shock absorber change so probably those connectors are okay...)



One time the car did not show any ABS warning light and I got the car started. (I don't remember exactly which relays / fuses / connectors I had messed with before that.) However, I didn't drive the car out of the garage, and after a while when I tried to start it again, the same warnings came on the dashboard and it wouldn't crank. So there might still be some hope to fix this Audi. But what should I check next?


And sorry for my bad English.

SMac770

If you have VCDS, then just provide the complete autoscan log unabridged. Do Save, not Print.

masalon

I don't have VCDS, yet. Another Audi guy came by with VCDS but it couldn't make connection to get the autoscan. So maybe this is also one hint for the problem?

SMac770

Oh, B6, not B8. Helps to put the right glasses on. So this is an old vehicle. I don't really know anything about the B6 electrical. But the scan tool being unable to connect is not a good sign. Assuming the Ross-Tech cable is a correct one for interacting with a B6. B6 predates DoCAN. It has CAN bus, appears three of them, but the OBD-II only connects to the car modules via the old K & L lines, which run direct to those modules present on each line. But I believe any of the recent era cables still have the K/L support in them. But it looks like you were able to read DTCs and clear DTCs, so it is interacting with the modules.

Yeah, the J217 (02-auto trans) is the mechatronics unit in the transmission. There were three automatics for the B6 4-cyl: the CVT (Multitronic) type 01J and the 5-speed ZF (Tiptronic) type 01V. Curious, back then the ECM (01-engine) was J220, not J623.

Sorry, can't offer much in this case. The B6 is simply too different in diag architecture from the B8 I know. You'll probably want to bring this up in the B6 A4 forum itself, to likely get more visibility on the query. As the root issue might be more than simply the FSI engine physicals.

masalon

This seems to be solved. Already checked the fuses couple of times, but eventually the problem was located there. Base of Fuse nr 31 was too open. Pried the gap a little smaller and after the cranked OK and gearbox was functioning.