1990 Pickup 3vze
My truck has been having hard cold starts lately, so I replaced a few basic parts. One of those parts was the distributor cap. After changing I tried to adjust the timing. I jumped the TE1 and E1 terminals in the diagnostic box and went to start the truck, and realized the CEL wasn't blinking like it usually does. So I stopped. and un jumped the terminals.

I then realized when I turn the key to ON The CEL light doesn't come on like it used to, and wont allow me to check any codes when the terminals are jumped. I checked the bulb, and I know its not burnt, because I switched it with the E brake bulb.
I searched around the forums and this problem is always paired with an engine that wont start. However. Mine runs great, after a hard cold start anyway...

has this happened to anyone else?

 

Something damaged the circuit to the bulb.

ECU damage ??

Squirrels eat the wiring over the last few years ??

Socket corroded you did check for voltage there with the ignition on??