Toyota Repair Problems? Ask a Mechanic for Answers ASAP
There may be a harness issue, but try this first.
Short a paperclip across pins 4 and % on the computer DLC connector and see what happens.
On the connector that you attach a scan tool with, there are 16 pins. The top row 2 center pins are 4 and 5. These are computer/chassis grounds. If you short across them, you eliminate a bad ground issue, so if everything starts to work normally again, you found you issue.
Thanks again, and please don't forget to rate me and keep this link in case you need me again later on.