Temperature Gauge not working

Hi,

First post. I tried the search engine as suggested and got so many unlated posts I gave up. My temperature gauge is not working so I'm going to replace the two temperature sensors first and see if that fixes the problem.

One sensor is easy to replace while the other is supposed to be behind the engine.

I've seen a Youtube video showing the replacement but this was on a V6 and not the 2.4 litre 4 cylinder version.

My question is where is the temperature sending sensor on the back of the engine on a 2.4 litre. This looks like a very cramped space to work in. Even more so than the V-6.

Is there a thread on this or can someone help me out on locating and replacing it. I have a new one on the way in the mail. Many thanks, BTW it's a 1999 Tacoma regular cab.

Lou

 

Welcome to TacomaWorld
On the block just above transmission bell housing

 

Hopefully this helps.

I committed a sin and searched outside of TW for this:

https://www.customtacos.com/threads/2rz-engine-coolant-temperature-sensor.155936/

Also a video that may help:
https://www.youtube.com/watch?v=rCeSPPXdRso

 

Why replace the coolant temp sensor when you don`t need to??

Your not sure if it is the sending unit has failed easy to test

just what happens when the ignition is turned on what does the temperature gauge do ??

 

Hi,

The gauge does nothing. No movement.

 

If you use an OBDII scanner, you should be able to see the coolant temp, independent of the gauge cluster.

 

Yes, I've used them. I'll have to find one to fit this year Tacoma. Assuming they have one that does and its not through the roof in price. Not sure if any critical lights came on when the gauge first indicated there was a problem. I just bought this car from the folks across the sreet. They don't remember the details. From what I heard Toyota has had a problem with temperature gauges on all their cars. Although I did own a Corolla many year's ago and the gauge always worked. I've also read that the sensor in the back is the one used by the dash gauge. Not sure what the readout would be on that device or how to interpret the Data unless I have a cross reference since those things are all coded with letters and numbers. I've never seen one that gives me a wrtten discription of specifically where the problem is. They tend to be general in where to point you.

The sensors are cheap so it moves a person towards the path of least resistance. I would like to know if that sensor in the back is going in from top down or sideways ? Anyone know ?

I need to pick up a mirror with a handle.

Thanks

Lou

 

OBDII is all the same the only difference is the other things it can do and the cost,

 

I thought the same thing... but my 99 Dodge with a Cummins doesnt support that PID.

 

Toyota does I have watched it to make sure it was working

My Ford 7.3 also shows the live coolant temp

 

Been around Toyotas most of my life, and I've never heard about a "problem" they have with temp sensors. 1st gen (6 lug) Tacomas certainly have a "thing" with our lower balljoints, but not the temp sensors. It's quite possible you may have just heard that from someone who had a problem with one, but I wouldn't say it's wide spread.

OBDII scanners were required on all vehicle built/sold in the US starting in 1996So any OBDII scanner will work on your '99. Newer vehicles can report more things to the scanner, but the scanner itself can work with almost any "modern" vehicle.

Just get one of those universal bluetooth OBD scanners and an app for your phone (I use Torque Pro), there's a free version, or I spent a whopping $5 on the Pro... Amazon has the bluetooth scanners for like $20-25.

The code readers can not only pull error codes (when your check engine light goes on) but will show you a whole litany of engine management data, like coolant temp.

With a cold engine, it should be within a few degrees of the ambient temperature. If you're getting pretty much any temp reading (the scanner will show you the actual temp vs. with the "dummy gauge" shows you) it's not the sender.

 

so, my needle is "stuck" for my temp gauge all of a sudden after 17 years. If I "tap" on the cluster housing it moves

@1943MB try tapping on it when the idle gets to normal and see if the needle moves. could just be a gauge issue and not a sensor issue

 

Test things before replacing. Don't replace the coolant sensor that the computer uses with a cheap aftermarket part. A cheap bluetooth ODBII scanner will show what temperature the computer sees. Most likely you'd have a check engine light if that sensor was bad.

The sender for the gauge could be unplugged or have a broken wire. You can also test it with a simple multimeter. All the sensor does is change its electrical resistance with temperature. If it's broken then most likely you'd get an open resistance reading (infinite). If you don't have a multimeter you can ground the connector to the engine briefly and check if the gauge needle moves. If it does this would be an indication the problem is with the sender.

Another problem I've seen is the nuts holding the gauge to the back of the cluster can become loose. The problem with this is that the nuts are what make the electrical contact with the wire traces on the back of the cluster. Tightening them up just a little will fix it if that's the problem.

 

I'm not sure if you got that info yet or not. The temperature sender for the dash needle is on the front, pass side of the engine (just at the upper radiator hose). It is 100% independent from the circuit and sender used by the computer. The sender for the computer is on the back of the engine, and it has nothing to do with your dash needle problem. If you engine runs fine, and no engine check light, leave it alone.

The sender used for the dash needle can go bad, but many other things could too. The first thing to check would be to measure the resistance between the sender's contact and the engine block. If it changes with the coolant temperature, it most likely is OK. May not be perfect but should act on the needle some. The next to test is the needle circuit - you can use a 300 ohm (or so) resistor instead of the sensor. When you connect this resistor between the sender connector and the ground the needle should jump up. If does not the problem can be in the instrument cluster itself, wire or the sender plug.

My guess it that the sender's plug contact is corroded and does not have a connection with the sender. This is really bad place (hot), and after 20 years that plug deteriorated in my truck completely.

 

I realized after the fact that I bought one of those OBD2 scanners for my 2007 Ford Focus. It's a Konnwei 902. So I spent the last half of the day trying to make it work. I down loaded the Torque App and now I would like to make it work since there's so much information that might be available. My problem is I can't get the phone to recognize the scanner in the car. I've done all the Blue Tooth gyrations I could find and still nothing. I'm still researching why it will not pick it up. Any advice would help. So the single wire heat sensor goes to the gauge. I need to pick up a battery for my multi meter. Thanks for all the information.

Lou

 

Mine has done that for as long as I've owned it - 80k miles. Not every time I start it but often enough that I know to tap the gauge.

 

Okay, I finally got my OBD2 to work. I went back and was looking at the box and it had a check mark on the WiFi and not the Blue Tooth so I switched to a WiFi connection. Now it's working. Have to disconnect the internet to do that. I got no fault codes. The thing that struck me was the coolant temperture reads 183.2 and the engine was only running for a few minutes. The dial was 3/4 all the way to hot. That doesn't seem correct to me but I'm not sure where the problem is. Anyone have a clue. All the other readings on the dials look correct. Here is a Youtube video that is using the sensor in the back of the engine to determine the status of the gauge or sensor . https://www.youtube.com/watch?v=VVJSwEakRto&t=62s.

Thanks,

Lou

 

The needle on the cluster doesn't actually read "temperature". It's an idiot gauge. The ECU sends a "filtered" signal that's based on the temp.

Haven't seen one in a while, but I used to see people post all the time about how they just installed a scangauge or OBDII reader and are concerned because their coolant temps move up and down as they drive, thinking there's an engine problem or maybe their dash needle is broken. But that's totally normal. The needle doesn't move up and down with variable temps unless it exceeds some warning threshold.

180 or so is pretty normal operating temperatures when it's sitting. Under load it'll easily get to 205 or so. So your sender is fine.

 

I know it is not exactly the same engine, but I think it is the same in that area. Here is my adventure with the "idiot gauge" on 1995 2.7.

https://www.tacomaworld.com/threads...k-or-rysium-build.457350/page-8#post-20756897

 

Hi,

Thanks for the info. At this stage I'm still a bit confused about the sending unit or sending units. So which one is the sending unit that tells the gauge what it should read ? If my OBDII is saying the temperature is good then apparently one of those sending units is good, or maybe both are good. Would it be safe to say that the dash gauge is the problem or is there a problem with either one of those sending units. Does one go to the ECU and the other to the gauge ? Or do they both send a signal to the ECU. Point being, if one of the sending units goes to the ECU and it's giving it the correct data but does not go to the Dash Gauge then the dash gauge is depending on the other sender to give it correct information. Which it may or may not be doing. I found the clip that goes over the rear sending unit but it does not come off easily and I'm not going to force the issue.

Thanks,

Lou