Temperature gauge freaking out

[krmccour]

So I was on a day-long road trip from New York to North Carolina and about half way through I noticed that my temperature gauge was having fluttering episodes. It seemed to happen randomly, and would correct itself within a minute or so. Essentially the needle would be stable, and suddenly it would drop down like I had cut the engine and would flutter all around (never above normal operating temps, always below) before suddenly correcting itself and returning to normal. I noticed no difference in how the runner was running, so I'm assuming its either the thermostat or a wiring problem? Anyone had this issue before?

 

[BrianSD_42]

This happened to me. It went on for months. I thought it was the gauge but when I took it to the Toyota mechanic he told me it was the "sending unit" which I believe is not located in the dash.

They swapped it and the problem hasn't come back since.

 

[BrianSD_42]

I think this is the part but I don't have my receipt handy.

BTW, I'm not saying, well I can't really say for sure that it isn't your gauge. But when I had this happen I was told its either the gauge or the sending unit.

If they offer to replace the sending unit they should only charge you 1 hour labor max. It really takes < 30 mins to change out and I was only charged $45 (1/2 hr) labor.

Pics .... Removed



layball:

 

[LittleCaesar]

Brian,

I think you meant the sending unit that fits in the back of the lower manifold. You were explaining the correct one, but the diagram is that of the fuel pump.

$25~$30 for an OEM one at the dealership. It is tucked right below the heater valve area. Start there, and if that isn't the cure, try the T-stat next.

 

[Doc2012]

There's 2 on our trucks. One below the heater hose on the driver side, another on the passenger side, below the fuel rail on the front of the enginge.

 

[BrianSD_42]

sorry for the confusion. I removed the pic.

 

[nevada]

There's 2 on our trucks. One below the heater hose on the driver side, another on the passenger side, below the fuel rail on the front of the enginge.

only one should send a signal to the gauge. the other should go directly to the ecu.

 

[krmccour]

Thanks for all the help guys. It steadily got worse yesterday, with the episodes becoming more frequent, with the needle staying completely down more frequently. It seemed to be correlated with the bumpiness of the road, but its hard to tell. Today I drove it 30 miles and it never moved an inch, so I'll check both those sending units and the wires leading in and out and see what I can find. Thanks again for all the info!

 

[krmccour]

So to conclude this thread, I recently bought some new shoes for the runner (in the form of Falken Rocky Mountain 285/75 R16's) because I was getting vibration from my old Nittos (dryrotting). Funny thing, on the way to get the new tires my temperature needle fluctuated even worse than it has before, and spent most of its time lifeless. However, after getting the new tires on which knocked out the vibrations, my temperature gauge has been working flawlessly. Who woulda' thought? :shrug:

 

[BrianSD_42]

OK so new tires have nothing to do with solving the problem. It's still broken.

 

[krmccour]

It likely means something is loose, not broken. Hopefully just a matter of checking the connections. So people with similar problems could possibly eliminate an issue with a connection loosened by bad vibrations instead of buying a whole new sending unit.

After getting the tires, I drove roughly 800 miles from NC to NY, and not once did the needle ever drop. Even on the pothole laden roads in Scranton.

 

[USS_Johnston]

Ok, sorry If I cause confusion here but I am new to message boards and do not know how to begin, nor can I locate a tutorial so, here goes.

Similar to the above post, I also have had an erratic gauge reading. When connected to a Bluetooth to phone scanner (OBDLinkMX) I can monitor the engine ECM reported temperature at 210. The gauge, however; moves up like normal(ish). After what was long distances and now only short distances, it climbs toward the red and beyond. If I shut it down and wait, the gauge will fall back into the normal zone, quickly. Since the scanner can read both it tracked the gauge going from 240 (apparently max) to 200 in about thirty minutes while tracking the ECM sender to have gone down maybe three degrees. Since physics basically prohibits the engine to drop that fast, when shut off an not under water or in antarctica (I am in central Florida) I am assuming that the sender for the gauge is defective. Now, I have trawled this forum and downloaded the various service manuals on offer as well as reading posts in regards to 4thgen 4.0L and I can not find anything specific to this. Nor can I find, in any of the books or online, where the bloody sender is located. I have purchased a new one and every search points to the engine ECM, which I have found on the engine and will replace once I find this little bugger. Does anyone have any idea where this sender may be located? For reference, I purchase both a Napa TS6677 and TS6678. The TS6677 is for the ECM and again, can see it. The TS6678 is, who knows. Anyone else have this problem or think I am barking up the wrong tree?

Model 2004 4Runner Driver Type 4WD - Grade SR5 Transmission - 4AT - 4 SP 4X4 A340F Transmission - Engine 6-CYL Date of First Use July 23, 2004

 

[Bad Luck]

Ok, sorry If I cause confusion here but I am new to message boards and do not know how to begin, nor can I locate a tutorial so, here goes.

Similar to the above post, I also have had an erratic gauge reading. When connected to a Bluetooth to phone scanner (OBDLinkMX) I can monitor the engine ECM reported temperature at 210. The gauge, however; moves up like normal(ish). After what was long distances and now only short distances, it climbs toward the red and beyond. If I shut it down and wait, the gauge will fall back into the normal zone, quickly. Since the scanner can read both it tracked the gauge going from 240 (apparently max) to 200 in about thirty minutes while tracking the ECM sender to have gone down maybe three degrees. Since physics basically prohibits the engine to drop that fast, when shut off an not under water or in antarctica (I am in central Florida) I am assuming that the sender for the gauge is defective. Now, I have trawled this forum and downloaded the various service manuals on offer as well as reading posts in regards to 4thgen 4.0L and I can not find anything specific to this. Nor can I find, in any of the books or online, where the bloody sender is located. I have purchased a new one and every search points to the engine ECM, which I have found on the engine and will replace once I find this little bugger. Does anyone have any idea where this sender may be located? For reference, I purchase both a Napa TS6677 and TS6678. The TS6677 is for the ECM and again, can see it. The TS6678 is, who knows. Anyone else have this problem or think I am barking up the wrong tree?

Model 2004 4Runner Driver Type 4WD - Grade SR5 Transmission - 4AT - 4 SP 4X4 A340F Transmission - Engine 6-CYL Date of First Use July 23, 2004

Welcome to the forum. This is the 3rd gen section (1996-2002). For more applicable information you need to be in the 4th gen section. https://www.toyota-4runner.org/4th-gen-t4rs/ Try using this google search to specifically look at 4th gen forum content while searching: https://www.google.com/search?newwindow=1&rlz=1C1QJDB_enUS784US793&sxsrf=ALeKk01FMrAycNlSBNvgj-SfJd8A-uTJzQ%3A1594760286298&ei=XhwOX9rJEcO8sQXf74DYDw&q=site%3Atoyota-4Runner.org%2F4th-gen-t4rs%2F&oq=site%3Atoyota-4Runner.org%2F4th-gen-t4rs%2F&gs_lcp=CgZwc3ktYWIQA1DPEliCIGDYM2gAcAB4AIABsQGIAZUEkgEDNi4xmAEAoAEBqgEHZ3dzLXdpeg&sclient=psy-ab&ved=0ahUKEwja8PaC0c3qAhVDXqwKHd83APsQ4dUDCAw&uact=5 Good luck