The '97 doesn't have the temp sending unit for the gauge at the back of the head. The only sensor it has is Engine Coolant Temp (ECT) sensor at the thermostat housing. The signals from it are provided to the PCM, which it uses to determine when the radiator fan should turn on and sends the digital temp data to the instrument cluster to drive the coolant temp gauge. If your temp gauge is jumping around you have a connection issue for the ECT sensor or in the wiring harness.


Examine the wiring at the ECT connector and at the wire loom at the end of the fuel rail to see if the fuel rail has penetrated the loom and n to the wires within.


Wiggle check the wiring with the engine up to operating temp so you have a temp gauge reading and with the key to ON/RUN (engine off) while someone watches the temp gauge to see there's a response to the wiggling.


Fuel rail penetration:



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