TEMP gauge gone nuts, pegs hot once key is turned.... but c

[CanuckQx4]

So I think I must have done something but I cant figure it out.

I changed my spark plugs and air filter on my 01 Qx4. Did not remove the throttle body to change the plugs, only had to remove the iacv and the coils and thats it. I overlooked all my connections again and everything seems straight

BUT.. When my car is running, the temp gauge goes and pegs hot, even if the car is cold. I dont know if its a coincidence that I just changed my plugs or what, but Id like the gauge to read proper. What would cause it to peg hot?? Some unplugged sensor??

[Chuck Tribolet]

If I recall correctly, the temp sensor is located on the front of the US driver's side of the block.

I'm impressed that you changed #6 plug with removing the throttle body.

[CanuckQx4]

Ya my mechanic buddy said I had to when he looked at my manual, but I simply pulled off the IACV with the 2 mounting screws and the ignition box came out with a little squeeze.

Im just curious what I could have done

[Chuck Tribolet]

The wire that goes to your temperature sensor is shorted to ground. I was wrong, it's at the right upper rear of the block, according to my FSM The wire is yellow with a
red stripe. You may have gotten it pinched under something (mounting screw for #5 coil?) There's a picture in the FSM, though it doesn't seem to match up to anything. I THINK I see the wire, but I don't want to mess with it just now. I just got home, it's hot and dirty there, and I still have my office clothes on.

[CanuckQx4]

Well Id like to get this fixed so I tried a few things, First I removed my air intake and checked out the entire drivers side bank to see if I perhaps pinched a wire, everything was perfect, nothing unplugged or pinched.

Then I put on new battery terminals since mine were looking pretty old a nd dirt.

So when I went to turn my car on, the temp gauge STARTS at 1/2 way up, then as it gets hotter, pegs out...

Do I have to reset something?? I tried it twice now in the last 2 hours, and it starts at half hot on the gauge and then pegs as it warms up

I also checked the coolant just out of percaution that it could be overheating but the coolant was fine.

I figure its an electrical problem of some sort.....??? but what do iknow

Thanks so far for your help

[Chuck Tribolet]

Check the passenger's side. The sensor is on the upper rear passenger's side.

There's an outside chance the sensor went bad. You can check that. Car cold, ignition on, you would expect (given your most recent experience)
to see the gauge at half. Unplug the sensor, gauge will go to zero with a bad sensor.

[CanuckQx4]

Well that confuses me quite a bit Chuck lol


Same problem today, car starts witht he needle at half, then warms up and pegs out. I pulled the plastic cover off again and everything is secure and connections are good.


I dont get what I coulda touched to make it do this but its making me angry !!!

[Chuck Tribolet]

OK, let me try again.

Start with the car cold.
Turn the ignition on, but don't start the car.
Give what you say above, the temp gauge should read half.
Now unplug the sensor.
If you have a bad sensor, the gauge will go to zero.
If you have a short in the wiring (other than the bit from the plug to the sensor),
the gauge will stay the same.


Chuck

[CanuckQx4]

Sorry im not the sharpest tool in the shed when it comes with cars lol, but that explanation I can do lol

I'll do it after work

Appreciate you typing that out thanks

[CanuckQx4]

Well the FSM points just like you said to the passenger upper rear for this sensor.

Anyways, with the ignition on, I disconnected each of these 2 connectors in the pic. But the needle stayed at half.


Then for giggles I did this connector aswell since I figured I may have got confused by the diagram but it didnt change anything either.


So does that mean my sensors working fine??

[CanuckQx4]

bump for pics

[Chuck Tribolet]

The bottom picture is the plug for the passenger side variable cam advance.

I think the top picture is the interesting plug. which is Sky Blue and should have (at least) the following wires:
yellow with red stripe. This goes to the "thermal sensor" which runs the temperature gauge. This is the one you care about.
light green with red stripe These next two go to the "engine coolant temperature sensor" which is an input to the computers that run the engine and transmission.
black

If that's the plug in the top picture, you likely have a wiring fault somewhere between the instrument cluster and that plug. It looks like that wire runs a short distance forward and joins a fat (1" OD) cable then runs in the fat cable back to the firewall, across behind the engine, then through the firewall. I'd follow that cable looking for some damage. If you can get at the instrument panel end of that cable and disconnect it (and the engine end) and measure the resistance between that wire and ground. It should be very high. The connector under the dash is a gray 16-pin whic will be very close to a brown 24-pin and a white 18-pin. Don't even think about turning the ignition on with
it disconnected. You will likely throw a bunch of codes.

[CanuckQx4]

bump for a little help, Im lost on the wiring check you posted last, dont quite understand.

But I did the test you posted 2 posts ago. When I turn my key, and the gauge instantly jumps to half even though its cold, then unplugged the sensor at the engine bay and the gauge stayed in teh same spot, which Chuck said meant it was wiring related

But what I dont get, is it seems to climb from there, would it not stay in the same position if it was a shorted wire? It seems to think half way is its starting point and pegs hot from there...

Would love to figure this out and run a new test wire to make sure everything is good working (sensor wise) and just to see the gauge work again. Thanks again Chuck

[Chuck Tribolet]

A dead short would cause it to peg immediately. But a short with the right resistance would cause what you are seeing. The '01 PF
FSM says that the resistance of the sensor should be:

47-53 Ohms at 212F (100C) (let's assume 50 Ohms)
170-210 Ohms at 140F (60C) (let's assume 190 Ohms)

And I just measured my with a cool engine (truck had been sitting for two hours with the hood up on a slightly breezy in the low 60sF.)

662 Ohms at 80F (30ish C)

MMM, Just looked at your top picture. That's the wrong connector. The one you want is about four inches lower and bit aft. And a lot
harder to get to, at least with my big paws. The one in your picture is for an O2 sensor. Unplug that one and see what happens. Hint,
it unplugs just like the one in your picture.

[CanuckQx4]

Ya I know that was the wrong connector, the one I need to test is this one.




How did you do your test and which prongs did you probe?

I just want this darn gauge to be accurate!!

[Chuck Tribolet]

First, what happens with the right sensor disconnected? What does the temperature gauge do when you turn on the engine cold.

Second, what you want to do is measure the resistance between yellow with a red stripe wire on the sensor (rear) side if the connector
and ground with a cold engine and report back. IIRC (check the colors, be careful, there's also a light green with a red stripe wire in there). And let us know which wire it was, the one closest to the block or farthest from the block (it's NOT the middle one).

[CanuckQx4]

I mentioned it up above but when I turn the key on with the car sitting overnight, the needle goes to 3/8th's the way up the gauge, then when I disconnect the sensor (key still on the whole time) the gauge doesnt change at all, stays in the same position. But if it is connected, the needle will rise and peg out to hot when the car warms up, but it started half way up the gauge.

I'll go measure that resistance, keep in mind the engine has sat for 10 hours in -5*C weather

[CanuckQx4]

So checking resistance between the yellow/red male pin and ground. I forgot when I went down to check if it was ignition on or off so I did both, and the numbers changed a bit so I figured it was worth a mention.

Ign OFF - 4.58K ohms
Ign ON - 4.85k ohms

I went back and forth twice on and off and got the same numbers both times. Outside temp was still -5 Celcius. My numbers seem to be quite different than what you posted, unless the K symbol my reader was displaying means something

Edit, so aparently K ohms is just a way to write it and the number Im getting is actually supposed to be X1000

So I was really getting 4580 ohms, and 4840 ohms on my readings.....

Maybe Ill go for a drive and get it up to temp then get a reading

[asnorton44]

[CanuckQx4]

And after a 10 min drive the resistance was 262 ohms

Dont know the temp on that though as the gauge was pegged hot

[Chuck Tribolet]

asnorton: that's the other sensor, the one that feeds the ECM. A different sensor (the "thermal transmitter") feeds the temp gauge.

Canuck:

Those resistances sound about right. However, it shouldn't matter whether the ignition was on or off. With the sensor disconnected,
it's disconnected, and doesn't care whether the ignition is on or off.

What did the temp gauge do when the sensor was disconnected? And was the pin you checked closest to the cylinder head or farthest
from the head?

Next step is to disconnect the sensor, pull out and disconnect the instrument panel and set it aside. Find connector M24 on the firewall
side (its the big one behind the tach). Pin 16 should be in the bottom row, fifth pin in from the door side and will have the same
yellow with a red stripe wire). Measure the resistance between M24 pin 16 and ground. It should show an open circuit (same as
holding the probe in air).


Chuck

[CanuckQx4]

They temp gauge needle stayed the same when it was disconnected, right at half mass (Ive never pulled the sensor after the gauge has gone to hot after driving it, to see if it jumped to half way after disconnecting) Ive only ever pulled the connector and looked at the gauge when the car was cold...

The pin I checked was closest to the head, I made sure it was the YLW/RED pin

I will go do that gauge cluster test right now as Im bored lol, I dont quite know what open circuit would be displaayed as but I'll report back, thank you for such detail on that last post. I really appreciate it, you could have linked me to the FSM page, and I would have been lost trying to figure that out

[CanuckQx4]

Did the test, found the connector and wire no problem. And I have 137ohms resistance at that terminal with the gauge cluster removed, and the connector in the engine bay disconnected.

Not good right

[Chuck Tribolet]

Not good, right. And that would pretty well explain what you are are seeing. Eyeballing the resistances in the FSM, that would put
the needle about midrange. Put it in parallel with the the sensor when at operating temp, you would see a very hot reading on the
gauge. (Rtotal = 1/(1/R1 + 1/R2)))..

It looks like you have a wiring fault. There's another connector between the instrument panel and the sensor FSM shows it's located
behind and below the radio. The Instrument panel side is called M33, the side the goes to the engine room is called F22. It's pin 4,
and yes, yellow with red. This connector has two rows of pins, one with nine pins and one with three pins, the latch and four more
pins. You want the latch side, the pin next to the latch where there are four pins. With sensor disconnected and instrument panel
out and disconnected, measure the resistance to ground. Odds are one side will show open circuit and the other show 137ish ohms.
The bug is somewhere on 137 ohm side.

I've got the CD-player out of my dash, so I can have a look at mine when it's daylight again (assuming it's not raining).


Chuck

[CanuckQx4]

Im really interested to see the actual cause of the wiring fault, like actually look at a pinched line or whatever BS caused this when I find it. Knowing what the connector looked like from a pic or if you can see it from the radio area or if its under the drivers side dash would certainly help if yours is already apart.

Pretty glad that I may not have to get that coolant temp sensor replaced, wasnt looking forward to that

[Chuck Tribolet]

You can figure that out from the FSM. In the EL section, in the schematics, it shows the connector layout and color. This one is "GY"
(gray). At the back of the EL section, it shows the harness routing. That will show you where the connectors are. Find the main
harness layout (that really means dash board harness). Look behind the radio in that and you will see the connector.

It's raining pretty good today (good, we need it). When it lets up, I'll have a look in mine

[Chuck Tribolet]

I went out and had a look at my truck. The plug is not visible through the CD player hole. I've got another place to look but it's raining
again.


Chuck

[CanuckQx4]

My cd player is a PITA to get out so Im almost relieved lol, sunny day here just freezing cold

I just put new stabilizer end links on all around this morning, hands are frozen

[Chuck Tribolet]

You are darn brave to work in that. Heck, I won't even work in the garage when it's 50F out there, esp. if it involves getting under.

It quit raining (weather radar says for a while) so I went out and had another look. No luck. They may be behind the heater ducting
somewhere. One option would be to cut out the factory wire and run your own from the instrument panel to the sensor plug. My
concern would be that wherever the problem is, there could be other wires damaged, or exposed to eventual damage.

[CanuckQx4]

Ya I was thinking of running a patch wire by simply splicing in after the gauge cluster, and running thru the firewall and over to the connector and splicing in on that side to, just to make sure it would function as normal again. But that would be kinda cheating and pretty difficult to splice in on the engien connector as its on the back of the engine with no slack

and like you said, where there's smoke there's fire lol