5ktq Possessed oil pressure auto check

[John Cody Forbes]

 It's interesting these days after 10 years and having owned 8 (as many as 4 drivable at once and currently 3) that 5000's can still come up with new issues to bug me. 

Patient: My "fast" '87 5ktq. 

Symptom: Auto-check oil pressure warning comes on only at idle and about 75% of the times the engine goes to idle (ie most stop lights).

 I have checked the black .3 bar oil pressure switch, it seems to do it's job correctly. Oil pressure via mechanical gauge is great. Tonight I unplugged and made safe the wire for the black switch and the problem persists. I did verify via bentley wiring diagram that the correct wire is on the correct switch.

Any BTDT before I start tearing in to this thing? The autocheck triggers on ground to mean low pressure so it can't be an intermittent open, it's got to be an intermittent ground or a bad autocheck.


-Cody (mobile)