The engine light comes on from low oil pressure,or high engine temp. w/o either present leaves the third reason assumeing warning module unit itself has not failed(Least likely):Failure Mode Effects Management
FMEM is an alternate system strategy in the ECA designed to allow improved vehicle drive should one or more sensor inputs fail.
When a sensor input is perceived to be out-of-limits by the ECA, an alternative strategy will be initiated. The ECA will substitute a fixed in-limit sensor value and will continue to monitor the faulty sensor input. If the faulty sensor operates within limits, the ECA will return to the normal Engine Running mode (strategy).
Code 98 will be displayed when FMEM is in effect.
The MIL `` Engine'' light will remain ON when the FMEM is in effect. The moral of the story: Run a KOEO & KOER scan. " ...And thy Scan results shall set you free" (Well, at least your know which sensors to replace. Start on sensors with actual "Failure" codes. a failed sensor can cause others to show "Out of range" errors. I 'm pretty sure my 87' 302 only has the one sender unit you were beatin the s**t out of, above & in front of oil filter. Note: I think the aerostar had something like you described that year, although someone forgot to mention its existence in the owners manual. Wild guess? Your ECT sens/switch aint reportin for duty. Also, The engine lite was the predecessor to today's CEL which in the beginning was easily and simply taken care of with a 1 inch piece of well positioned black electrical tape. 2 inches if it aslo bugged the passenger too.
Last edited by ymeski56; 10-09-2008 at 11:23 AM.