OBD 2 connector not communicating with ECU

[sonnybr4life]

I have a 1999 audi a4 1.8t quattro. I tried using a vag-com, and regular snap-on scanner and it will not communicate with vehicle. The steps I took were:

1. Test K-line with resistor, K-line not problem.
2. Disconnected ABS module as it was not functioning.
3. The mechanics took 2 gallons of water from electrical compartment.
4. All fuses are good.

I did a little research throughout the forum and the above procedures are what I could find, and they did not solve problem.

Other problems with vehicle are:

AC fan went crazy and starting smoking, so I disconnected plug.
Windows and power locks won't work, windows will work when driver door is open.
Car has 160,000 miles on it.
front lip came off, and there were wires hanging in the front. Wires were cut from previous owner, I put wires together. OBD 2 was fine when wires were cut.
Throttle is off after i disconnected battery to reset computer. It has happened in the past, but with vag-com mechanic was able to reset codes and throttle would work fine. Check engine light is on, and the code showing before the obd 2 connector stop communicating was about a speed sensor.
Catalytic converter has been welded, but check engine light was off after the weld job. Both O2 sensors were replaced after weld job from 1 year ago.

Please help?

[sonnybr4life]

bump. anyone? ECU bad?

[Chris@RevoUSA]

Is this an automatic? did anyone pull out the tcu (passenger seat floor area), they are known to flood and can be shorting out the port.

[Audi0s]

Is there an aftermarket radio in there? Sometimes they get power from pin 1 on the obd port, which is usually hot 12v. This could be interfering with communication

[sonnybr4life]

its a manual.... no we havent done that yet.. so the tcu is located under passenger seat? I bought an used ecu.. gonna change that monday or tuesday.. i'll have a look at tcu...

[sonnybr4life]

There is no radio in there.. we checked the k-line and reading is fine.

[dozanti]

Regardless of radio or no radio, take the fuse out for the abs, its on the top part of the fuse box, low amp. Take it out and connect the scanner, and it should work. I spend an hour outside in the snow trying to communicate and it wouldnt. I pulled the radio and all the above. My last option when i had the scanner connected, I pulled the abs fuse and it immediately connected. Try it and let us know if it worked for you also

[sonnybr4life]

I tried disconnecting the fuse for abs, and the the scanner wouldn't even work. I replaced the ecu, and the airbag light came on with the new ecu. The scanner still does not communicate with vehicle. My last option now will be to replace the obd 2 port connector. Someone told me that the pins inside could get lose and break. Is that true?

[sonnybr4life]

I had an accident with the vehicle few years back and the airbag deployed in the back. The light never came on until i put in a new ecu. I'm going crazy I have been spending so much money.. Mechanics don't even wanna touch my car... I brought it to an audi specialist place and they didnt even wanna look at it.. This other electrical place wants to charge me 200 just to "start" looking at it.

[sonnybr4life]

today i removed the ecu and ecu casing took off plugs under ecu cleaned them with electrical spray... checked the box by firewall, some relays and circuit fuseshad water stains i tested them and they are all good.. I poured some electrical spray on the connections and still nothing... wednesday i will replace engine speed sensor which is why the light was on in the first place.. after that I have no more ideas on why the scanner is not communicating.. any ideas anyone?

[sonnybr4life]

HELP Please!

[ricekikr]

Does the OBD port have power? Try replacing the fuse for the OBD, even if the fuse isn't busted (sometimes fuses don't work properly even if its visually intact). I forgot which it is exactly.

If it has power, there goes my theory. Goodluck =)

[sonnybr4life]

Does the OBD port have power? Try replacing the fuse for the OBD, even if the fuse isn't busted (sometimes fuses don't work properly even if its visually intact). I forgot which it is exactly.
If it has power, there goes my theory. Goodluck =)

Ill try doing that... thank for the reply im going crazy no mechanic wants to help me out which sucks..

[sonnybr4life]

Does the OBD port have power? Try replacing the fuse for the OBD, even if the fuse isn't busted (sometimes fuses don't work properly even if its visually intact). I forgot which it is exactly.

If it has power, there goes my theory. Goodluck =)

Actually it does have power.. i just dont get it.. im try to work on it tomorrow. If not its going to the auto electric place 200 just to start looking at it ouch...

[dozanti]

The K line is being shorted or disrupted by something. Pull the harness out for the radio and make sure everything looks okay. I swear I pulled my abs fuse (top right corner of fuse box on drive side dash) and it immediately connected

[jstoner0007]

sonnybr4life, did you ever find out what the problem was? I have an 01 TT and same issue and I can't get my car to pass inspection. I have the factory radio, all fuses are fine (going to try removing the abs fuse after work), no check engine light. The only thing out of the ordinary is my passenger side floor does get wet after heavy rain but my car is manual transmission so I think that eliminates the TCU. Man, electrical problems are the worst to have.

[un1ko]

I'm now having this issue did either of you figure out the issue? I'm going to try to take out the ABS fuse and see if it works.

[Rob3069usmc]

Anyone figure this out? I have tried all the above and nothing.. I have a 97 A4.

[rlny]

reviving this from the dead......I am having the same issue the fuses to the left of the dash look good. I was told to check the fuses under the engine bay but I am not sure which fuse to check. any help would greatly be appreciated. I have an 01 audi tt by the way.