On my 92 XJ if u turn the key on, off, on, off and back on all within 5 seconds the check engine light will flash and pause and then flash again.You have to count the flashes,it is always a 2 digit code. That's how I knew my TPS was bad and when changed it, it fixed my trans. If you call 1 of the auto supply stores and they can probably tell you what the computer says.