Sitting here looking at a GM TBI un it and wondering... I can see the TPS (throttle posistion sensor) And figure out what it exactly is but WTF is the secondary sensor on the TBI body??? Is it the air temp sensor??? I'll try to get a pic. The TBI unit is at home right now. Okay, try this pic. The TPS is at the end of the butterflies the other sensor is in the middle left hand side of this pic.