Scan help

[Donut_steve]

Hi,
Anyone in the Tonbridge area could help to check my Golf 3 diagnostic socket works ?

Geezer who was doing my new keys could not get his tester to communicate with the car so I'm stuck until I can prove its working.

Thanks
Steve

[bearthebruce]

Do you have an aftermarket radio in the car? If so, it probably is hanging the comms with the tester. See this page:
http://www.ross-tech.com/vag-com/aftermarket-radio.html

[Donut_steve]

Thanks for the reply.
Theres no radio at the moment.
I had read that link and thought it related to later models - my car is a 1996.

Steve

[Donut_steve]

bump :approve:

[bearthebruce]

You need to get a meter out and check the status of the pins on the connector. If the voltages seem correct, then you have control module in your car that is hanging the diagnostic bus which will prevent all other modules from communicating. Only solution for that problem is to unplug modules one at a time to find the offending module.

[Donut_steve]

Bruce,
Thanks for the info.
I have checked the socket with a meter.
Getting 12v on 16 and chassis ground ok on 4.
Have not checked the K+L lines as I wasn't sure what I should see.

Is there any info you could point me to on what should be on those pins ?
Then I'll start disconnecting things !
Thanks

Steve

[bearthebruce]

The signal on the K Lines are digital signals. If they are working properly and data is moving on the lines, then there should be some voltage other than ground or +12. Take your metter with one lead referenced to ground. If you read something on these pins between say 1v and 9v, then you can assume all is well. If you find you are reading +12 or ground, then you have a problem somewhere on the bus.

The instructions for measuring the K Lines on the Aftermarket Radio Problem page still apply here:

If you have a volt-meter: measure the voltage between pins 4 and 7 of the diagnostic connector with the ignition and radio turned ON. If it's under 9V, your K-line is fine. If it's over 9V, the results are inconclusive. You'll need a 1k Ohm (approximately) resistor. Put it between pins 4 and 7 of the diagnostic connector. Now use the volt-meter to measure the voltage between 4 and 7 (in parallel with the resistor). If it's under 1V, you don't have the problem. If it remains near 12V (the resistor will get hot!) you do have this problem and you'll need to fix it per the the instructions below.

If you have done these voltage tests and find nothing wrong at the socket, then you must a controller that is tying up the bus. Start unplugging the controllers one at a time until you can communicate with the a module.