Close - The knock sensor is down there, next to the CTS for the ECU. The Renix Jeeps have three coolant sensors, one in the back of the head for the light/gauge, one in the bottom of the block by the knock sensor for the ECU, and one in the radiator for the fan. In 91, with the HO system, the one in the bottom of the block, and the one in the radiator went away, replaced by one in the thermostat housing. (knock sensor also went away with the HOs).