While in heavy Rush hour traffic I noticed coolant temperature approaching hot?

Tiny
CA7922303
  • MEMBER
  • 2016 TOYOTA RAV4
  • 4 CYL
  • 2WD
  • AUTOMATIC
  • 90,000 MILES
Driving in heavy rush hour traffic, sometimes not moving (idling), noticed coolant temperature approaching hot. Turned engine off, let cool down below 1/2 and reentered interstate, now at near interstate speeds. Made in home about 18 miles and temperature gauge never passed 1/2. I'm thinking stuck/unstuck thermostat or nonfunctioning radiator cooling fan. Please advise.
Tuesday, February 25th, 2025 AT 6:14 PM

17 Replies

Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 54,144 POSTS
When the engine was hot did you hear the radiator fans running? How is the coolant level? We need more information on what was happening. It could be may this that can cause this including radiator fan failure, blown head gasket, coolant leak or a bad thermostat as mentioned.

Here is a comprehensive guide to help us get started on fixing the problem:

https://www.2carpros.com/articles/engine-overheating-or-running-hot

Here is how to change the thermostat which might fix it. Check out the images (below). Please upload pictures or videos in your response of any problems so we can see what to help you with.
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Thursday, February 27th, 2025 AT 11:30 AM
Tiny
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Fans were not running, little to no coolant loss. No fans operating with A/C on or off. No A/C.
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Saturday, March 1st, 2025 AT 8:36 AM
Tiny
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Jumped relay on fans 1 and 3 and fans are operational. Fan 2 would not jump. Swapped relay for fan 2 and no change. Not seeing a temperature control sensor in bottom of radiator to jump. There is a switch that sits on the bottom left side in front of radiator looks like an ambient air sensor. Not finding any fuses inside the passenger compartment for fans. Should I jump ECT switch connector on top of engine?
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Saturday, March 1st, 2025 AT 10:30 AM
Tiny
KEN L
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No need, if there are no codes this shouldn't matter. Is this a hybrid car? I only see two fans for the non-hybrid car, here are the wiring diagrams for the cooling fans so you can see how the system works. I would start by checking fuses ECU IG3 in the fuse panel on the left side of the dash and fuse RDI fan and CDN fan fuses in the fuse panel under the hood.

This guide can help:

https://www.2carpros.com/articles/how-to-check-a-car-fuse

Check out the images (below). Please let us know what happens.
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Saturday, March 1st, 2025 AT 11:09 AM
Tiny
CA7922303
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Also, I hear the A/C compressor kicking in and the refrigerant is in the green on the gauge, but no A/C, only warm air.
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Saturday, March 1st, 2025 AT 12:22 PM
Tiny
CA7922303
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RDI and CDN fuses look good (photo). Non-hybrid engine with two (2) fans. Fan 3 relay is both fans on low speed. Fan 2 (A/C fan) is not operational when jumping relay but is operational when fan 3 relay is jumped.
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Saturday, March 1st, 2025 AT 2:35 PM
Tiny
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Saturday, March 1st, 2025 AT 2:40 PM
Tiny
KEN L
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The ECM controls the fan operations, let's plug a scanner in to see what the engine temperature says. You could have a bad engine coolant sensor. Also, let's check the ground for the system which is located at the right front of the engine compartment, (blk/wht wire).

https://www.2carpros.com/articles/checking-a-service-engine-soon-or-check-engine-light-on-or-flashing

Here is the location of the coolant sensor in case the reading is way off. Check out the images (below). Let us know how it goes.
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Sunday, March 2nd, 2025 AT 11:45 AM
Tiny
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AutoZone code reader shows P0500 and C1439. Also, will an A/C compressor kick in with proper refrigerant level, but not blowing cool air due to fan not operating? I previously stated this was occurring with this issue.
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Saturday, March 8th, 2025 AT 4:54 AM
Tiny
KEN L
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These codes have nothing to do with the fans not running, and yes if the fan do not run the AC will not work. It could be the ECU not commanding the fans to come on. The white wire to the ECU grounds and turns fan 1 and 2 on, and the red wire turns fan three on, I would remove the connector form the ECU to ground them manually to see if the fans come on, this will tell us for sure what the problem is. Please use the wiring diagrams above to help. Here is the location of the ECU. Check out the images (below).
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Saturday, March 8th, 2025 AT 10:19 AM
Tiny
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Any way you could send the location of the white ground wire to ground out on the connector? Unable to determine which white wire. Thinking pin location on connector would do it.
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Sunday, March 9th, 2025 AT 10:48 AM
Tiny
KEN L
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It just says "right front of engine compartment" Alldata does not give the connector view pin out, sorry. You might need to dig into the wiring to find it, also it could be wht/blk as well. Have you found the ground location inside the engine compartment?
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Monday, March 10th, 2025 AT 10:29 AM
Tiny
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No, not sure about ground location in engine compartment.
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Monday, March 10th, 2025 AT 1:12 PM
Tiny
KEN L
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Yep, they don't show images just the location descriptions. All we can do is check the power and grounds and if okay, it looks like the PCM might be bad, you can send it in for testing.
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Tuesday, March 11th, 2025 AT 10:00 AM
Tiny
CA7922303
  • MEMBER
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I'm getting (5.0vdc) at the temperature coolant sensor. Is there a way to test sensor itself, or is it a sure bet that the sensor is bad and causing fans to not run and a/c to not work, since there is voltage at that connector?
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Sunday, March 30th, 2025 AT 1:47 PM
Tiny
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Replaced temperature sensor and fans and A/C are operational. Thanks for your help. Appreciate it.
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Saturday, April 5th, 2025 AT 10:35 AM
Tiny
KEN L
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Glad you could get it fixed, thanks for letting us know. Have a great weekend!
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Saturday, April 5th, 2025 AT 11:51 AM

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