Hi all, new to this so bear with me.
I bought a 2001 Ford Ranger 2.3L a few years ago. Everything was fine with it for awhile. However I noticed that every once in awhile the heater wouldn't work which didn't really bother me because I live near Sacramento and it gets to about 40 degrees at lowest. However 2 winters ago I noticed every once in awhile the temp gauge would peg at over heating. I would check everything and it was fine. Get back in and start it up and all would be normal. The problem stopped after winter. Last winter though I went on a road trip with a friend and the gauge would be at normal running temp and then peg it as high as it could but would still run. We got out a couple of times and checked everything. But everything checked out. Since I'm a poor UC Berkeley student I decided to take my chances and I just kept going. About the fifth time this happened the engine lost ALL power when I was in about 4th gear. We stopped for 2 hours and had lunch got in and the gauge automatically pegged it at high. Before even moving an inch the engine killed itself again, however this time the temp needle dropped WAAAAAY below the coldest spot and the check engine light came on. After that the engine ran fine and the temp needle hasn't moved since nor has check engine light gone off. That was about 6 months ago (I know I neglected my car and this is automotive karma) but now it has started running roughly and lurching while driving uphill at about 3000 rpm and upon flooring it. I borrowed the guy from autozones obd-2 scanner and it told me there was a problem with the engine coolant tempature sensor (though my year and engine size doesn't have one). I replaced the Cylinder Head Temperature Sensor assuming it was in lieu of the ECT and unplugged the negative terminal (obviously) and my check engine light turned off, car started idling well, no jumping on uphills or full acceleration, but temp needle stayed bottomed out, for about a day and a half and then the check engine light came back on but temp needle started registering around 1/16th of the way, major improvement though it doesn't sound like much, at hottest. The guy with the obd-2 scanner wasn't at autozone today so I am waiting until friday, when he works next, but was wondering, in the meantime, if anyboyd has any suggestions. I am sorry about the long post, I just didn't know what was relevant. Thanks in advance.

 

Might be an old thread, but I'm putting this up for other to see in case it helps.

A 2001 truck could be either Single OverHead Cam (SOHC) or Dual OverHead Cam (DOHC) because the DOHC engine was introduced mid-model-year.
I'm going to take a chance and assume yours is a DOHC based on what you said.

There are 2 coolant temperature sensors on your engine:

There is one that reports temperature data to the gage on your dash - it is built into the thermostat that is mounted on the engine block behind your water pump on the driver side of the engine. Unfortunately the thermostat is an unusual design and as a result is (for a thermostat) extremely expensive, $140+.

The other one is mounted on the waterneck at the back of the engine on the passenger side. If you follow your upper radiator hose back to the metal pipe (waterneck) and follow that to the spot behind the cylinder head where it bolts to the head you'll find this ECT sensor. The price for this one isn't to bad because its a normal design, should be around $30.

There is some debate about which reports what to the computer.
1 - I replaced the ECT sensor on the waterneck and it did not fix my problem (no temp reported to gage), so I can only speculate it reports its data to the PCM.
2 - I bit the bullet and bought that expensive thermostat - that fixed the no temp problem. I've also read that after the first couple of years that engine was used in our truck the super-expensive T-stat got replaced with a less expensive one (I think I read it was something like 2005+) that works just as well and fits the same pigtail.

If you want to see some pictures, check out this thread: (pictures are down at the bottom of the thread)
https://www.ranger-forums.com/dohc-2...t-sensor-8063/