Lazy Daze Owners' Group

You can pull codes on pre obdII but it is not as easy peasy as modern readers. The connector is not under the dash and may be in various locations in the engine compartment. My connection on my 1990 is near the firewall above the battery and is two connectors held together under a little cover that says "EEC Test".  You take off the cover and connect the two female connectors to a code reader. It is totally possible to get it upside down. You have to look at the house shaped connectors and match them up. The one I used is this one:
Amazon.com: INNOVA 3145 Ford Digital OBD1 Code Reader: Automotive
The book of codes that comes with it is probably worth more than the device and is quite complete. There is the engine off code testing and the engine on testing. The engine on testing involves using an extension cord for the device because you need to turn the steering wheel and do other things to check sensors. I had no idea that there was so much early automation going on even in my 30 year old chassis.  I just checked engine off and it worked great. Compared to my obd II reader this is way more involved but the only other alternative involves a paper clip inserted in the correct connection and counting the times the check engine light flashes inside the cab. It's on YouTube.