OBD-II scanner won't read my car's computer

[mfitz]

My 98 1.8t is running great, no CELs, or any other issues that i know of (except one, i will get to that) but i had to take it in for annual smog testing. I went to two different places, but neither could get their diagnostic machine to get a reading on my car's computer.Any ideas why?

My ABS controller is shot, but i can't believe that would interfere with a scan tool, would it? Or, is it possible that my OBD port is just busted/ disconnected somehow and needs to be replaced/repaired ? Has this happened to anybody else? I didn't see anything like this while searching the forums.
I have 30 days to get this sorted out before i have to take my car back in for a retest, so the sooner the help the better. thanks in advance.

[mfitz]

did more searching and found thread saying it could possibly be due to aftermarket radio/head unit? Any ideas any one?

[Rusty]

Bump.

I'm no expert, but I thought the aftermarket radio issue wasn't an issue on the older ('98) cars.

The ABS module is a different module than the ECU. Emissions should only check the ECU. I don't see why a busted ABS module would cause OBD-II scanner to fail. But who knows? Not me.

Do you have anyone close to you with a VAG-COM? That might tell you something - if a VAG-COM doesn't work, you may indeed have a cable problem.

Have you ever had the lower dash off? If so, the OBD wires may have gotten pinched, or pulled off the connector.

[Johnny]

I've seen where the connector got pushed up a little and when you plug the scanner in, it can not read your ECU.

Take off the fuse side cover and reach in to re-seat the connector. Works better if you have girly arms

[turtle]

did more searching and found thread saying it could possibly be due to aftermarket radio/head unit? Any ideas any one?

The local shop I use told me they would not connect their scan tool to a VW with an aftermarket stereo because they had ruined two tools and refuse to fry a third.

[mfitz]

thanks everyone. i hope that it is simple as a loose connector. i will check it out tomorrow in daylight. Does anybody else know for sure if the aftermarket radio problem is confined to newer models?(If so, chalkup another point for the AEBs )

if that is the problem, i do have the original radio and can put it back in if necessary.It would just be a pain in the ass, but at least it would be free.

[brettgrant99]

My 98 1.8T Variant has an aftermarket radio. It passed emissions no problem. That was about 2 months ago.

I don't know if that helps you.

Brett

[Trader_Reed]

My 98 1.8t AEB Variant won't scan unless the factory radio is installed.

[wheresjim]

I have the same problem. I also have the bad ABS controller, and I have a stock head unit. When Herman hooked up his Vag-COM we couldn't access anything except the ABS related stuff. I'm pretty sure it's the ABS, but I am getting my ABS rebuilt this week, so I can check to see if this fixes the problem.

[mfitz]

thanks for the extra input everyone.

i felt up under the dash and the port seems to be seated securely. i haven't tried to look at it yet through the fuse panel opening. there is a chance i knocked something loose last year when i installed my column mount boost gauge, snakeing the hose through the dash.

wheresjim- keep me up to date on your progress if you could, thanks.

[deleontow]

If you have a bad ABS control unit it can cause communications problems with the scan tool. Try disconecting the control unit and see if you can communicate. This is a common problem with this car. If it is not and you have an after market radio check the aftermarket connectors there is a blue wire that is looped, cut the loop and it should allow you to communicate. The blue wire is looped from the electric anntenna signal and the K wire.

David DeLeon, VW Master Technician

Diamond Valley VW, Hemet CA

[mfitz]

what is a K wire?

[Urlik]

what is a K wire?

http://www.ross-tech.com/vag-com/aftermarket-radio.html

[quality_sound]

If you used a Metra wiring harness then the K-Wire is a non-issue. Metra doesn't even put a wire in the K-wire slot anymore because of this. Of course if your installer (or you if you did the install) is worth his ass he'll have properly connected the HUs power antenna lead to the powered antenna adapter and not the dash harness.

[98vwfan]

I had the same problem that you had. I ended up diconecting the aftermarket radio and took it to the smog test. It worked fine.

My 98 1.8t is running great, no CELs, or any other issues that i know of (except one, i will get to that) but i had to take it in for annual smog testing. I went to two different places, but neither could get their diagnostic machine to get a reading on my car's computer.Any ideas why?

My ABS controller is shot, but i can't believe that would interfere with a scan tool, would it? Or, is it possible that my OBD port is just busted/ disconnected somehow and needs to be replaced/repaired ? Has this happened to anybody else? I didn't see anything like this while searching the forums.
I have 30 days to get this sorted out before i have to take my car back in for a retest, so the sooner the help the better. thanks in advance.

[mfitz]

Of course if your installer (or you if you did the install) is worth his ass he'll have properly connected the HUs power antenna lead to the powered antenna adapter and not the dash harness.

i seem to remember a second trip to Best Buy to get the powered antenna adapter, but that doesn't mean i hooked it up right

i also already checked in the dash and didn't see any loose or disconnected wires.

the plan now is to disconnect the radio and try again at the test center, and if that fails, disconnect the abs controller and try one last time.

if none of that works, six of these might help. :biglaugh:

[mfitz]

http://www.ross-tech.com/vag-com/aftermarket-radio.html

Ahhhhhhhhh! great info.

[mfitz]

late update- removed aftermarket radio and the scan tool read my car just fine. thanks again to everybody for their help. I also identified the k-wire( there was a tag on it on the adapter harness saying "do not connect this wire on model year 95 and up VW's" ) and I clipped it, so hopefully i won't have to pull the radio every year.

matt

[red2526]

Hi, I have the same problem. I get to reading.

I have a bad ABS module and I have the original radio that come with the car, no work has been done under the dash board or near the fuse area. It fail the smog check because it could not read the computer. The tech reset all codes and drove it for 15 miles and returned to the same place, still it could not read the computer. Since I have the original stareo it should work, Now I have to check if any wires are loose and try again. and it not then I need to get the ABS module replace, incase this is the case.

Any thoughts.

Thank You

[mghunt]

If you used a Metra wiring harness then the K-Wire is a non-issue.

Very true, however the older wiring harness adapters are typically the issue.

When I bought my harness adapter in '98 it has the K-wire looped and I had to cut it because I had scanning issues.

So, to correct Rusty (gasp), it is an issue on the 98's as well. :biglaugh:

-Mark

[vagbestech]

Hello, I would like a help with my 99' passat AEB 1.8t tiptronic. I don't know if I'm in the right topic. After a heavy rain, my car had its floor flooded with water due to clogging of drains under the battery. I had to change the tiptronic gearbox module. For reasons of high cost, I bought used module and the car ran ok. VAG Connecting OK too, But 15 days later, dashboard turned on the ABS light with 3 beeps, intermittent, with increasing frequency until it lit constantly. At this time I only can connect VAG modules as engine, autotrans, etc except ABS when the ABS Module is unplugged. I sent it to a guy in Ebay located in California, (MODULE REPAIR PRO) who said he repaired the module but, surprise, I placed it in the car but the lights on dashboard but not turned off. How could I check for failures in the wiring harness or this have something with respect the replacing of tiptronic module? Or would test the repaired module with the multimeter?

[Steve in Chicago]

Your scan tool connects fine as long as the repaired ABS module is not connected? If that is the case, it appears the repaired module is the problem.

[vagbestech]

Yes, if I disconnect the abs module, VAG communicates. The problem is I have 02 modules and I find it unlikely that both are bad. Anyone know how can I test the abs module or my car wiring harness? Thank you very much!