http://www.cygnusx1.net/Supra/Librar...px?S=Main&P=48
Sounds like the EGR Gas Temp sensor used in Cali model vehicles. Do you know if the car was originally sold in the CA market? Is there an EGR temp sensor installed? What's the part number on the ECU? (it's the one in the format of XXXXX-XXXXX) It may be a CA model or just have one of the more complete wiring harnesses.
At any rate if it is a CA model you'll get an error code if you leave it unplugged; If it's not then there will be no issue.