Engine coolant temperature sensor replacement - P0117

They are generally just squeeze and pull. When they've been there for ten years it can be a little more like squeeze and persuade, but there shouldn't be much more to it.

P0117 means there was a moment, at least half a second long, where the ECM thought there was a short in the circuit to the coolant temperature sensor.

What was your process to ascertain that the problem is in the sensor itself and not in the wiring?

I think the sensor is a simple thermistor and (never say never, but) probably isn't very likely to go bad.

 

When I see a connector like D6, all I generally do is squeeze the tab and pull the connector off. Yes, sometimes they are in awkward positions, and sometimes after being on there for years they are a bit recalcitrant, but there isn't any specific releasing tool needed. Sometimes you just need to see what you've got around, and improvise.

When you see something like this in the repair manual,



while the "trouble area" column is usually organized in a rough order of likelihood (in this case suggesting you might first look at the possibility of a wiring short), that isn't exactly the same as instructing you to "change this thing, then change that thing, then change the third thing." It is giving you the possibilities you need to gather evidence about in order to determine which thing to change.

As you see, that list suggests considering first the possibility of a wiring short.

Looking through the rest of that nine page diagnostic section in the Toyota repair manual, the only two places it would tell you to replace the sensor would be after step 2(i) or after step 3(g). Both of those places you only reach by first confirming that the wiring is OK and that the ECM reads as expected when you substitute a known resistance for the sensor.

It's curious that you seem to have seen a "Toyota repair manual" that gives ECT, thermostat, then short etc., in that order. Can you say more about where you found that?

 

It’s true that the electrical connectors are made to be released without a special tool, and Toyota’s publications don’t mention one, but there are connector housing pliers designed to make this job easier. See, for example, the KTC AD101 (page in Japanese), also on page 149 of their English-language catalog (55 MB PDF), or the Muromoto Tekko (“Merry”) HS175C (page in Japanese). I have the latter, sold at a discount by amazon.co.jp.