Plain Jane OEM nothing to see here rebuild

[Pete_89T2]

Originally Posted by JustJeff

One question related. The water thermosensor:
I'm curious if it would work to test the water thermosensor for resistance but at the ECU pin rather than the sensor itself?

Reason being, to test per FSM means removing it, draining coolant, etc. Is there any reason why I can't start with a cold engine to test resistance at the ECU and let the engine warm up while testing?

The problem with doing it that way is your DVM/ohmmeter puts some voltage across the terminals you're trying to measure a resistance across. If it's still connected to the ECU with power applied you could potentially harm the ECU. Also, unless you have a good aftermarket temp gauge, how will you know the water temp when you're taking the resistance measurement?

Assuming you do have a temp gauge, one option would be to run the car until warmed up, then jot down the water temp off the gauge and shut it down. Disconnect the battery. Then disconnect the ECU connectors, and do your resistance measurement across the two ECU harness connector pins that connect to the water temp sensor. That will only get you one test sample though, so you still won't know if the temp sensor works across its full range. IIRC, the FSM gives 3~4 temp points to measure resistance on that temp sensor.