I've got the same problem and I just checked on 50resto... why the heck is the 90-93 sensor $20 more than the pre-90 sensor?! I guess it just comes down to what's more annoying... having a dummy light that's constantly on or paying $70 to replace a lying sensor. Has anybody replaced their sensor and had it fix the problem?
'90 GT: 331 w/ TFS top end kit, chip, T-5, full exhaust, Autometer mechanical gauges, 3.55, MM SF connectors, FRPP LCA's, 5-lug swap, C/C Plates, SN-95 brakes w/ SS lines, '93 Cobra MC, Cobra R's w/ Kumho rubber, E-fan, cold A/C.
'87 LX Hatch: 2.3 converted to 5.0, 4-cyl T-5, "Type R" floormats.