Jeep Wrangler - How to test a coolant temperature sensor.

[@Poweraddicts]

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[@lindorm90]

2 years later and this video still saved my butt.. thank you!!

[@Poweraddicts]

+Rudy Maciel Glad it still works for you! :-) Thanks for taking the time to leave a great comment! Have a great day!

[@lifelong5425]

Dang son, your videos are so on point with the real check overs on these engines...very helpful...thank you

[@condor4679123]

Thanks for the video. I have moved on form the temperature gauge not working to not showing the correct temperature. There are a lot of online part stores that indicate temperature senders will work with a model of Jeep but you need to make sure that the ohm specification of the sender is correct for the gauge on the dash.

[@Poweraddicts]

Stoneyburke That sensor helps the engine know how to mix the air\fuel ratio and adjust the timing. Without it, it can throw lots of different fits. Dieseling being one of them. They aren't very expensive or get one of similar year from a salvage yard. Wire it in see how it acts. Getting a sensor from a salvage yard will also give you the chance to get a replacement plug for your melted one.

[@spooks9999]

I love your videos brother, my jeep was running like a crap and basically not drivable. Got 22 flashes on check engine. And got this code. Thank you so much can't wait to have my old girl running like a top again

[@Poweraddicts]

Glad to help

[@howardfamily1212]

Good video. Practical, direct and as simple as can be. Thanks for the extra information on your website, too.

[@richardduncan7381]

I really appreciate your videos, you've been a great help to me the past few weeks as I've been working through issues with my (new to me) 87 YJ 2.5L. One thing that I do have an issue/question about with the temp sensor, is how do I find it on my engine? I don't have a temp sensor on my thermostat housing, and no place up there for there to be one. I've seen a couple of others with the same issue, but it seems very difficult to find anything about where it's located on the Throttle body manifold(?). If you can sometime find the opportunity to make a video about this, it would be most helpful to those of us with the 4 banger and slightly different configurations. Cheers and thank you for making these videos!

[@izzynutz2000]

On my 1993 Jeep 4.0 that sensor was throwing me a fit if I shut the car off the injectors would flood out and the car wouldn't start I would have to press the gas pedal to the floor to get it to start. It would spit sputter like it it flooded out it controls the timing in the distributor and it also controls the rich and lean factors of the injectors I change that sensor out and all my problems went away

[@antiricergt]

have you done a video on the rebuild for the 2.5 yet? I just got my 1st Wrangler with a 2.5 auto. It's a 94 with 4in rough country lift and 33x12.50s.

[@tsmith578]

Hey Chuck, When I test the 5 volt reference Circuit for the coolant temperature sensor on my 1995 4 0 litre. With the sense unplugged and the key in the ON position. The voltage fluctuates between 4 volts and 5 volts at all different readings. Have you ever seen this before ? All the other sensor circuit voltages stay at a steady reading when they are tested the same way. All the wiring has been tested and is good, and I changed the ECM with a different one and it tested exactly the same. I am asking because the engine has been running rich at idle and having a misfire at idle. The sensors test ok according to what you say in your video , which also matches exactly to what it says in the shop manual I have.. Unless I am somehow testing the sensors incorrectly. Or they have a internal short and I don't know it. Please let me know any information you may have about the 5 volt reference Circuit fluctuation. Thank you, Tim from Wisconsin

[@JessHines]

Do you need the pigtail, or can you just put the leads on the poles of the sensor itself? I'm trying this, and not getting any continuity between the poles. Like, my multimeter just shows 1.

[@johnappleseed4504]

I need to test both mine on my yj.temperature on gauge goes screaming up but obviously is not running that hot

[@deanrigdon5992]

the wires came out of the 2 wire harness that connects to my ECT. Does it matter which one goes on the left or right? Thanks

[@dembrowi_n_c.5111]

I did your test, my CTS was faulty so I replaced it. I checked resistance on the pigtail just for kicks and I have 4k on the pigtail w/o the ignition or anything on. Is that correct? Any information would be appreciated.

[@enriquemeza7366]

I have a 2001 Jeep Wrangler sport. I drove the jeep about 75 on the highway and it did fine. But then I drove it another 25 miles and the engine bay has smoke coming out of it. I pulled over and check it and it had coolant all over the engine bay.. At first I though it was a radiator hose but when I tightened that one up it kept doing it. Does this sensor tell the Jeeps computer when to turn on the radiator fan? The fan is on the first 5 minutes of starting it up but then my check gauges light comes on and it starts to smoke again. Please help!

[@stanlouis458]

Thanks for sharing your knowledge, much appreciated.

[@Poweraddicts]

+Stan Louis You are very welcome. Thanks for taking the time to leave a message! Have a great day!!

[@rogerbahr9117]

Can that sensor cause the gauge not to work 100% if you replace the rear one already

[@Poweraddicts]

The sensor up front has no control over the gauge. If you have replaced the rear one, need to check the wiring or gauge cluster.

[@tomashton7208]

I have a 1990 yj wrangler with the 2.5, my vacuum was 14 inches at 3200ft, so I installed a new chain, and the vacuum went to almost 18 inches, any how I have some problems, there is no sensor on the thermostat, and last winter when I got the jeep it would start right up, first issue, no thermostat, so I put a 190 temp on, so im looking around a the back of throttle body and there is a MAF sensor on the intake, and a coolant temp sensor in the water jacket of the manifold, both sensors have the power wire spliced into the main harness at the fire wall Im thinking somebody did and engine swap with out the harness for that engine, the egr is disabled and it has an oxygen sensor on the exhaust manifold but no converter, I live in the mountains and there is no emission standards. All of the sudden it runs rough and wont idle, and it was fine until I dsiconnected the battery

[@nickphillips8682]

How so you check blower motor resistor

[@dustbunnysafari]

I keep getting a engine running too cool reading......????

[@internetnomad1444]

I recently replaced the temp gauge in my YJ. The temp reads between 225-240. is this normal? The gauge never worked until now. I also changed the radiator and flushed the coolant recently.

[@Poweraddicts]

It shouldn't read above 210ish.

[@BrettHoustonTube]

I have been having a weird overheating issue for years on my 98 TJ. Typically happens in Summer, going uphill on the freeway, with a load of gear, running AC. The alarm will sound. I shut it down. Wait 20 minutes and go on. It could do this 5 times on a 3 hour trip. It has never boiled over or vented steam from the cap. Sometimes I would just shut the engine down, coast and and start it back up in 30 seconds and it would reset and I could drive for another 20 minutes. Never happens off-road. Never appeared to actually overheat, although I never took the cap off while it was hot. I have replaced the thermostat, radiator, fan/clutch and such over the years to no avail. Water pump seems tight, no wobble, no leaks. I picked up a water pump just in case the blades are shot. Thinking of switching it out. Wondering if that is it, or maybe it’s just a bad sensor that triggers the alarm? What are your thoughts?

[@ccopelandofficial]

Hey I think I'm having the same problems... Did you figure it out? I've also gotten a new temperature sensor and radiator (both a year ago). What happened to me recently was that the alarm would sound that it was overheating and so I would shut it off, wait, start up again. But one time I couldn't pull over so the alarm sounded for about a minute and then alarms stopped, went all the way to cold, and a lightning bolt icon popped up. Did this ever happen to you?

[@johnappleseed4504]

You could boil the water then remove from element then test

[@jaimesustaita5216]

Hello sir,I bought a cylinder head but didn't notice it didn't have the hole where sensor in the back goes,,is there anything I can do to fix that?

[@markthompson4885]

My Temperature gauge does not work . I just found out my replacement block does not have hole for sensor in the rear eather. DAM it.

[@edvardhribersek6621]

You are very helpful to me. Thank you.

[@jaimesustaita5216]

I'm in the same situation,were u able to find a solution?

[@Poweraddicts]

Changed the sensor.

[@LubardiTV]

*Please Help* I have a 1993 jeep wrangler YJ with a 2.5 in it and i recently changed the valve cover gasket and added some coolant and look at my temperature gauge and it is just below 100 and i know its not running below 100 because it had been running for some time so i go and look at the coolant sensor and i un plug it and take it out and clean it up and put in back in and it still dosent work and then i checked some wiring and see one little plug unplugged and i find where it plugs back into and i plug it back in and still the gauge reads below 100 and then i ground the plug that i found and then tha gauge reads over 260 does anyone know whats going on?

[@Poweraddicts]

Assuming you are checking the one on the backside of the head. The front sensor in the water neck is for the ECM. Sounds like a bad sensor to me. They aren't very expensive to purchase to see if it fixes it.

[@LubardiTV]

alright thanks will do

[@arthurc1971]

What is the name of that wrench ?

[@Poweraddicts]

Its an adjustable boxed end wrench. Super handy!! Craftsman only made them for a short time. Thanks for dropping in!

[@FrankyRevolorio]

Where is it on an 89 2.5l?

[@FrankyRevolorio]

It’s behind the throttle body to the right of the egr, there’s a heater hose connecting close to it

[@tatchik77]

What if I don't have one of those plugs to use? Can I just touch my tester leads to the prongs inside the sensor?

[@Poweraddicts]

Yep, that would work just fine. I've done it several times. Thanks for checking out the video! Have a great day!

[@tatchik77]

@@Poweraddicts Thanks for the quick reply! It's reading about 25% higher than the max for each temp so I will replace the sensor. But my temperature gauge never reads more than 175, is that normal?

[@geberhard]

Awesome videos, thank you!!

[@Poweraddicts]

Glad you like them!

[@martinw9425]

Always learning something with new you ,i thought that front coolant sensor WAS the gauge sensor!!!!! so i did change it and nothing happen, so i thought that wasnt the problem,......i have a hayne shop manual wich i gave a thumb down and a thumb up to ya.......good work!

[@Poweraddicts]

Thanks! Glad I could help!!

[@b.mendiola2515]

Is it normal my temp drops from 210 to 150ish then worms up to 210 then drops again every few min? Its a new radiator from stock 91 yj

[@Poweraddicts]

B. Mendiola If you recently installed the radiator, sounds like you have still air in the system. It may take a day or two to purge it all out. Make sure you keep coolant with you and top it off when its low. Put coolant in the reservoir, each time the engine cools it may pull coolant from the reservoir tank to help burp the bubbles. Hope that helps :-) Thanks and have a great day!

[@b.mendiola2515]

Alright thanks man. I'll give it a shot. Thanks for your time :)

[@Poweraddicts]

You are welcome. Hope it helps.

[@patrickab01]

Love all your videos I bought step son a 94 yj. Replaced valve cover and ripped the corroded sending unit sensor apart Found after market put in and tore it to pieces putting it in Bought another one and only went in tight enough to where it wasn’t leaking. Still see threads so I’m guessing it isn’t all the way in. I was a bit afraid since I tore up the first one I put in. Now car is reading hotter than normal. What are your thoughts ? Should I try to get it all the way in

[@Poweraddicts]

What temp is it reading? Temp at 195 - 210 is normal for Jeeps. If the sensor has stopped going in, dont force it any farther. The threads are tapered, if you force it anymore it will split the water neck. Have a great day!

[@66windar]

couldn't you just use an infrared sensor pointing it at your rad hoses?

[@Steve_Just_Steve]

Thanks man.

[@Poweraddicts]

You are welcome. Hope the serves you well!! Thanks for checking out the video and taking the time to leave a comment!! Have a great day!

[@eduardo9163]

Why not just check it in the thermostat housing with some alligator clips. That way you know what the resistance is in its natural habitat.

[@GusgusA1]

0:59

[@SUPERSTUD6000]

it would be easier just to buy a new one if you think it is faulty

[@Poweraddicts]

+barry soetoro True .. but then that wouldn't make as much of an educational video. Thanks for dropping in. Have a great day!

[@dizzywillow2162]

seems like a lot of work to test a cheap part. I would just replace it and get on with my day. good video though

[@Poweraddicts]

I agree. I'd personally just throw a new one on and call it good. The part is probably $10 or less. But, some people like to test every little bit so I created the video to demonstrate what they need to know. Have a great day!!

[@jo-jobighiker5552]

Use a Heat gun.

[@Poweraddicts]

Yep, that would work.

[@kevindeibler346]

But i want to know more about the other one lol

[@Poweraddicts]

All the other one does is run the dash gauge. Its o inexpensive its not worth testing. But tell tell signs can be the single post sticking up it moving or can be pushed in like a spring ... its bad.