For the last few months my Bronco goes into diagnostic mode briefly after I start the engine. The KOER test initiates where the idle goes up then drops along with a few blinks of the engine light and then everything is fine. It doesn't do it all the time. It doesn't matter how long it has been sitting when it does it.

I am wondering if anyone else has had this problem and knows what the probable cause might be. Thanx in advance!

 

The test sequence is triggered by shorting the STI to Sig_Rtn or ground so maybe trace those wires to see if there is a short or bare wire somewhere.

 

have you tried to pull codes to see what is being stored?

 

Not yet since I don't have an OBD 1 scanner available. If I cannot come across one I'll just use a jumper wire and count the blinks if I have to.