I took my car in for a smog check yesterday and expected it to pass easily but I was disappointed. Emissions passed but the shop wasn't able to hook up to get diagnostics. They guy told me I had some type of electrical problem and that I'd have to get it fixed before going back. Luckily, his counterpart overheard the conversation and asked if I had an aftermarket radio. He mentioned all I had to do was remove the radio to make it work. He was right, after pulling the radio the check went fine.

I did a search but didn't find any info in the forums so I thougt I would post this tidbit. I expect that there may be some who can't get diagnostics from their car due to this. Here is the entry in the California smog check inspection manual. Sorry if this is redundant.

Make

Volkswagen

Model Year

1996-

2002

Model

All models with

non-OEM stereos

Problem

If the OEM stereo has been

replaced with an aftermarket

stereo, these vehicles may

not communicate with the

analyzer and/or OBD code

scanner and may cause

severe damage to the

analyzer/scanner. For more

information, see VW

Technical service bulletin 02-

03 dated June 10, 2002.

Action

BAR recommends that you check with

your analyzer/scan tool manufacturer to

determine whether or not your

analyzer/scan tool has complete

current/voltage override protection.

Override protection will protect the test

equipment in cases where aftermarket

installations cause over current

conditions. BAR’s June 22, 2002 ET

Blast provides a method of checking for

high voltage conditions using a test light.

An alternative is to send all 96-newer

VW/Audis with non-OEM radio

installations to a VW/Audi dealership for

verification of proper OBD function.