Well I visit here about twice a year now when I'm stumped on something that's busted on this damn 4Runner that my GF drives. I’m having issues with the Coolant Temp Gauge. It’s a 3.4L Limited (1996).

Here’s what I’ve done so far: Changed Coolant Temp Sensor.

This is what I’ve diagnosed so far: I’m getting 5volts to the sensor. The Sensor does change in resistance as it heats up so I know the new sensor isn’t bad. I disassembled the gauge cluster, took out the coolant temp gauge, and bench tested it. I was able to actuate the needle by applying 1.5volts (AA Battery) to various points of the gauge. I put everything together and still nothing. The needle still doesn’t move.

I’m fairly sure that’s all that would be involved with this simple gauge. Or is there a sender/receiver somewhere between the sensor and gauge in line that I’m not aware of?

TIA!

The GF would really appreciate it!

 

Sorry to state the obvious, but are you sure it's not the thermostat?

 

What's the problem? Is the 4Runner overheating?

 

Cant help until you post more pics of GF

 

What he said, more pics and we will see if we can help you out.


P.S. Make sure that the wires going to the gauge are getting voltage at the gauge...

 

There are 2 temp sensors, one for the computer and one for the temp guage. The temp guage, Toyota calls that the water temp sender, is at the back of the engine and the computer one, called the engine coolant temp sensor is at the front. Which one did you change.

 

No it's not overheating; the gauge just isn't registering (stuck below cold). If it moved a little then I’d attempt the thermostat cause even a free flowing T-Stat would let the coolant get a little warm.


I changed the one at the front of the engine. I asked the dealership if there was more then one, they said "no". So is the 2nd one (the back of the engine) the same type/style as the front?

 

there is only one on the 5VZ motor, and that is the one at the top front
of the engine. It sends temp to the ECU for running the engine, and then
dashboard gets it signal from that as well.

Hook up an OBD II scanner that can read temp, and verify and isolate
if the sensor is good and the dashboard is bad. OBD II should tell you.

If OBD II also reads nothing, you should be getting a MIL lamp too,
cuz half the emissions depends on the coolant temp sensor readings.

 

I am staring the the official toyota manual right now.
where is the second sensor ?

because on 5VZ engines, there is only one thing sending water temp.
the one on top front of motor under the fuel rail bridge (fuel pipe).

and Toyota official name for it is ECT sensor. the only thing toyota calls 'water' on this 5VZ is the water pump. educate me please.

 

Well I'm thinking it's got to be the gauge then. (If there’s only one sensor- I called the dealership again, still only one sensor for the temp. There’s one in the back but that’s for the EFI)

During my diag tests, when I unplugged the connector to the front temp sensor, the idle went low and I got MIL. When I plugged it back in, the RPM's went up a bit to a more normal pace. Disconnecting the battery for a bit reset the MIL, then I go on test drives, Temp gauge never moves, no MIL's. So that tells me that the ECU is getting what it wants...just not the gauge.

 

The factory wiring diagram I have shows 2 sensors. That's for a 2001 4Runner, other years with the 3.4 v6 may be different. Like I said the guage gets a signal from the water temp sender, and the computer gets a signal from the coolant temp sensor. I haven't actually verified this by checking my engine though.

 

gosh dang you are right. two sensors, independent.

this thing won't let me post pictures, but the engine compartment diagram
shows both. I learned something good today.

 

Could you e-mail that diagram to me please?


petegalle@gmail.com


Thanks!

 

sent a 5VZ pile of docs to you. it should apply
to any 5VZ 1996-2001 in general.

 

Awesome man, thank you! I'm going to pick up that Water Temp sensor and install tonight.

 

I decided on my lunch break to get the part and switch it out. And it worked! It was the sensor on the back of the engine. Man I've never been so excited to see a needle in a gauge move before.

Thanks again for all the help!

 

Glad we could help. Now about those pictures of your girfriend...........

 

hahaha... yeah dude pay up. we wont tell anyone.

 

Yeah and let that dealership know how stupid they are. Telling you wrong not once but twice! They should know. Bet they didn't even bother to look at a diagram or pull the info from the computer. I'd be hot i'd shove the parts guy's face under the hood and show him!!!

 

yeah

I can understand ME being wrong, just some random chump on the intertubes, but the dealership should KNOW, or at least say. "we don't know
let's check with a Master Tech."