I have a 1990 b2600, check engine light came on and Im trying to pull the code. I grounded the single wire plug by the wiper motor and used a paper clip to connect the terminals of the plug next to it. I can get the LED light to come on but not flash. What am I doing wrong, thanks. I have been messing with this for awhile starting to feel really stupid

 

 

tried that already

 

There are no codes AFAIK. OBD1 was introduced in 1991 and died in 1996. Not all vehicles had it, and I'm pretty sure that none of the B-series trucks did.

 

The manual lays out how to check for codes using the way I described. I was able to get the LED light to flash at one point then when I went to record it I was not able to make it flash again. damn