99 Accord F23A1 - Mystery Sensor Installed in Cylinder Head Under the Distributor
 

Can anybody possibly tell me what the sensor circled in red is? It's number 15 on the parts diagram, and none of the online Honda parts stores seems to have a listing for it. The pigtail for it is single-wire, which leads me to believe that the sensor itself might generate a voltage (i.e. thermocouple)? Thanks

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That's the sender for the dashboard temperature gauge.

You have the wrong parts drawing. #14 on the picture is the VTEC oil-pressure switch & #15 is a bolt for those models that don't have the switch.
Instead of that, look at the picture titled "Water Pump - Sensor" and it's #14.

Great, much appreciated!

PS the one that's full of oil in your photo is the engine-coolant temperature sensor (signal goes to the PCM as opposed to the dashboard gauge).

Good to know, thanks. Distributor o-ring failure. Both of those sensors are getting replaced. You have any idea where I might be able to find a pigtail for the dashboard sender, besides the junk yard? Leaking oil made the old one brittle to the point of cracking.

Nevermind, looks like they're a standard 3.9mm bullet connector. Thanks

ps- haynes claims that this sender was annuled in 2001.

Starting 2001 the PCM sends its temperature signal to the gauge, but prior years the PCM doesn't "share" that signal. So you still need that in a 1999 Accord.

probably only in american cars. i got 2 heads from 2002 that still have both senders, japanese made.

Oh yeah. Sorry, I keep forgetting you're not in USA. Lots of things are different by country.