You don't need any external system to check the codes on either of the type of ECU which the MKII came with. I believe that the '85 has the TCCS system in which case diagnosis is the same as it is for the MKIII. Refer to the MKIII FAQ section for a thread on checking diagnostic/error codes.
__________________
If something breaks or you need to contact a member of the administration please post HERE. Unless it's a private or administration matter please post it on the forum. It benefits no one else if car related questions aren't posted for future users and takes away from the time I'm able to spend helping on the rest of the forum.
If you're so inclined I'm always more than happy to accept tips via PayPal. 
Tip Jar ---> 
|