ECT switch, sensor or sender ? planning to replace

[fenixus]

i was thinking also about replacing ECT sensor. i'm unsure, but hard to believe that my engine coolant temperature inclines so high (over 212F) at idle with no accessories running and gets low again whenever driving or using A/C. would need to double check this one with some thermometer.

perhaps ECT sensor output impacts ECM fuel trims at idle on top of oxygen sensors readings ? i've seen in another thread that person replaced it and gained nice MPG boost (back to normal). wondering if it would help me.

part price is inexpensive ($20-30), so i'm eager to try that if it might help.
looked at rockauto.com but got confused, there are coolant temperature switches, senders and sensors ? which one is it ? is ECT sensor the one sitting in bottom of radiator of 5s-fe (gen4)?

when checking dealer for oem part i found only this:
http://www.toyodiy.com/parts/p_U_200....html?hl=83420
gage assy, water temperature sender

83420-AA010 $18.84 at toyotapartsoutlet.com
is this it?

[LynchburgCSI]

I can't input anything about the problem itself, but for the part, try looking for it on http://www.rockauto.com/catalog/raframecatalog.php ...They have diagrams to show you EXACTLY what part your buying. They don;t always have the best price... but it's handy for looking up stuff.

[fenixus]

Originally Posted by LynchburgCSI

I can't input anything about the problem itself, but for the part, try looking for it on http://www.rockauto.com/catalog/raframecatalog.php ...They have diagrams to show you EXACTLY what part your buying. They don;t always have the best price... but it's handy for looking up stuff.

thanks. i looked at them and pics of sensors and senders look more or less same to me, though they are separate categories ...

[haux]

Which one are you looking to replace, the engine coolant temp sensor that actually goes to the motor, or the ECT switch that goes to the radiator? I have no idea what the "sender" might be.

You can use the diagrams at toyotapartszone.com to find where it's physically located, and get the part numbers that way.

One of the them is slightly smaller than the other. I believe the sensor going to the motor is the smaller one. You can always remove yours and compare. Then, once you know what they are supposed to look like, you can buy the proper one on RockAuto. However, the body size of an aftermarket ECT switch will probably be slightly larger than OEM (it was in my case). The sensor part that goes inside the radiator was the same.

I really suggest going OEM in this case though. A $30 ECT switch I bought at an auto store failed after 2-3 years. I know OEM prices can be pretty high. I think the engine temp sensor was about $36, and the ECT switch was around $70.

[93celicaconv]

Fenixus, I wish I had the service manual for your 2000 Solara SE 5S-FE, but I don't. It would help me a lot to tell you for sure what the issue is.

Not having it, here is what I "think".

Your radiator fans are not coming on when the coolant temperature elevates. The fans, when they are on, pull air through the radiator to keep the coolant in the radiator cool, so when the coolant is pulled into the engine, it keeps the engine coolant at the proper temperature. You should either have a radiator mounted temerature switch that controls the radiator fans, or your ECT sensor is used via your ECM to turn your fans on when needed.

When you drive, you are pushing air through the radiator to keep the coolant in the radiator cool. You don't need fans running when you are driving, at least at highway speeds.

When you have your A/C on, that control automatically turns your radiator fans on, mostly to pull air through your A/C condenser coil, but of course it also pulls air through your radiator too, so your radiator benefits.

So it sounds to me your radiator fans do work, as they seem to function properly when you use your A/C system. But they don't work when your A/C is off and your coolant temperature gets to high.

I'm thinking your ECT sensor is the problem (this is making the assumption you don't have a temperature switch mounted in one of the tanks of your radiator). The ECT sensor plays a major role in your electronic fuel injection system as well. So if this ECT sensor isn't calibrated properly, you could be getting poorer fuel mileage as well.

The 83420-AA010 part number is not the correct part for your needs here - that part is the one that only drives the temperature gauge in your instrument cluster. And that circuit seems to be working well.

Using your ToyoDIY.com link, and clicking on the Electronic Fuel Injection System category for your car, you will see part number 89422-35010 (Sensor, Water Temperature (for EFI)), which I believe is the correct ECT sensor you are looking for. Looks like the price is $70,81 from ToyoDIY.com. 1stToyotaParts.com sells this part for $45.67. An automotive store like Advance Auto Parts has it as a BWD Coolant Temperature Sensor, part no. WT653 for $23.69. O'Reilly has this part as a Master Pro (also part no. WT653) for $13.99. This is also an extremely common sensor, so many Toyota's dating back as far as 1989 would have them, something that could be picked up from a salvage yard for next to nothing.

You are looking for the ECT sensor with the wiring harness connector that has 2 pins (not the one that has 1 pin, which is the sensor that drives your temperature gauge in your instrument cluster).

Hope this helps.

[hill8570]

93celicaconv gave ya the part numbers. ECT (the sensor that the ECU uses for coolant temperature measurement) is right near where the upper radiator hose enters the engine -- it's the far-left (usually green) connector. This sensor is more than just fuel "trim" -- it's one of the major inputs for the injector pulse width. A sensor that is reading higher than coolant temp is going to give you a too-lean mixture, and the O2 sensors will have to trim rich to get it back...not sure if that's what you're seeing.

FWIW, the temp switch that controls the radiator fans is down on the lower passenger side of the radiator.

[93celicaconv]

Hill8570, then his 2000 Solara does have a radiator temperature switch then. I didn't know it used this control for turning the radiator fans on. But since it does employ this control, Fenixus should first replace the radiator temperature switch, as that may be defective.

Fenixus, in a control circuit that uses a radiator temperture switch, if your remove the wiring harness, then run the car, the radiator fans should run at high speed all the time. If they do, then you know your wiring is OK and your radiator temperature switch is defective. You might want to try running your car this way to see if it eliminates your overheating problem at idle (I think it will). Then go replace your radiator temperature switch.

[fenixus]

wow! i feel i was on right tracks finally when i posted it last night. sorry for late reply, but i took a day off and was sleeping long, got sick over weekend (nice sinus infection gives me enough headache...)

initially i wanted to post this in my 11 page long thread about 5s-fe fuel trims - in short that was about my problem ECU based on o2 sensors (now both new NTK) makes it rich so MPG goes down whenever driving with fuel loop closed (e.g. steady cruising on highway or idling in parking lot). decided to start separate thread to gain a bit more attention and more answers

car is after full tune up (NGK+OEM), after 1 sea foam treatment,now also with new o2 sensors (NTK upstream and downstream). I had 2 water pump failures in past, the original one was just loud, but second aftermarket was leaking from weep hole after i flushed radiator (because earlier mixed 2 aftermarket fluids, they got brown color which scared me) and switched to TLLC coolant mixture, now running again new OEM pump again (TLLC coolant). i suspect something is adding up to poor cooling system in my car and it might be electronic related.

thanks 93celicaconv, camry gen4 manuals as per engine, SFI, cooling, powertrain, etc are exactly same as for my gen1 (camry) solara, thanks for your explanation. i should have the sensors in radiator just like any camry does.
so should i unplug the lower radiator fans temp switch to make the test?
the upper one sittin in engine, 89422-35010, 2 wire sensor in rad would be an ECT sensor for ECU ?

i understand that the one with 1 wire (83420-AA010) sitting in rad is irrelevant as it feeds only the dash gauge (works fine i think) and is not the one feeding ECU, right ? it does however control the fans, right ?

thanks hill for confirmation! what you described is EXACTLY what i am seeing. something causing mixture to go lean at closed fuel loop (this is also when OBD2 shows coolant temperature starting to grow up) and ECU makes strong positive trim adjustment. they go away when i'm pressing harder on gas pedal (open loop) which also causes to bring coolant temperature down (even slow local driving with short acceleration bursts does that, might be also wind adding up to it).
Coolant temp also always go down when A/C is turned on (fan on). so another vote for ECT sensor in engine

haux, thanks bro for opinion on aftermarket sensor! i will go OEM on this, was chasing ghosts in my car for so long, that i don't want to risk another unknown variable in this riddle. thanks for pointing out size (diameter) difference between engien vs rad sensors, they actually are different, now i see it.

so, please based on above confirm which one is most likely culprit, being sick makes it uneasy for me to quickly understand all of this hehe, feeling wimpsy a little...

I'm about to order 89422-35010 from toyotapartsoutlet.com this evening. pls let me know i'm doing the right thing now
or i should test (how exactly) the other one first ? or maybe i should replace both of them ? let me know pls.

[93celicaconv]

You have a lot of things going on at the same time. You should probably work one out at a time to resolve.

From my perspective, no, the 1-wire 83420-AA010 sensor does not control anything except the output of your gauge in your instrument cluster.

If you have a temperature switch mounted in your radiator, then that temperatuer switch is what controls your radiator fans (in addition to sensors in your A/C system). Just disconnect the wiring harness to that temperature switch to see if your radiator fans come on full speed all the time. If they do, then you know that temperature switch is defective and needs to be replaced to help avoid future overheating.

I can't comment on your 2-wire 89422-35010 ECT sensor being bad, now that we know you have a radiator coolant temperature switch. But it is possible the 2-wire ECT is sensing coolant temperatures improperly and affecting your fuel trim values, since your ECM determines fuel trim in large part by the output coming from this sensor. You can test the resistance values of this sensor against a resistance chart when the sensor is in a water bath of known temperatures to see if it is outputting the proper resistance according to a chart that matches up output resistance values against known water temps. Then you would know for sure. Otherwise, I would just get a couple of these sensors from a salvage yard and put one in to see if it resolves any of your fuel trim issues. I hate paying a new part price on something when I'm guessing at what the problems are - so salvage yards come in handly for that.

[fenixus]

uhm, i think the only sensor in rad is the one for dash gauge, but i may be wrong cause i don't know much about it....

hill also said the ECT sensor in motor might be my problem's root cause affecting both coolant temp as ECU sees (and what obd2 reads) and poor fuel trims. i don't mind getting a new one, it's a nice feeling to have brand new plugs, wires, filters and o2 sensors, now time for ECT and let the quest completes

i'm tired of testing and measuring hehe, since i would have to remove it for testing I will get a new sensor and see how it goes.

keep your fingers crossed. thanks guys!

do i have to drain coolant from rad (draining engine block is out of question for me) to replace this sensor and avoid coolant spillage ?

[93celicaconv]

No, Fenixus.

Your dash temperature gauge reads the temperature of the coolant as it exits the engine through the water oulet. It does not measure the temperature of the coolant in your radiator.

I wish I had a service manual for your car, but I don't. I do have a 93 Celica with the 5S-FE, and that car has 3 coolant sensors:

- one in the water outlet housing, a 1-wire sensor, that drives the dash temperature gauge
- one in the water outlet housing, a 2-wire sensor, that feeds coolant temperature information to the ECM
- one in the bottom tank of the radiator, that switches the radiator cooling fans on based on the coolant temperature in the cold tank of the radiator.

Because someone said there was a temperature switch in your radiator, I am assuming your Solara has a similar setuup to my Celica.

You did say you have an overheating problem, right? And that your radiator fans don't operate unless your A/C is on? If you have a sensor in your radiator, then your ECM doesn't control the fans on your radiator, so your ECT sensor doesn't have an effect on turning your radiator fans on or off. Now, if you don't have a temperature switch in your radiator, then we have a different story. But someone said you did.

[hill8570]

Originally Posted by fenixus

uhm, i think the only sensor in rad is the one for dash gauge, but i may be wrong cause i don't know much about it....

Nope -- like I said, dash gauge sensor is right next to the ECT, right where the upper radiator hose enters the engine. Temp switch for the fans is on the bottom passenger side of the radiator.

Originally Posted by fenixus

do i have to drain coolant from rad (draining engine block is out of question for me) to replace this sensor and avoid coolant spillage ?

You don't have to drain coolant to replace the ECT, although you'll want a rag around the area to catch dribbles. If you replace the fan temperature switch on the radiator, yeah, you'll have to drain the radiator. Won't have to drain the block, 'tho.

[93celicaconv]

Originally Posted by hill8570

You don't have to drain coolant to replace the ECT, although you'll want a rag around the area to catch dribbles. If you replace the fan temperature switch on the radiator, yeah, you'll have to drain the radiator. Won't have to drain the block, 'tho.

First, test to see if the radiator temperature switch is bad by removing the wiring harness and see if the radiator fans come on when the engine is on.

If so, what I have done regarding this particular sensor, is leave the engine cool down overnight. Don't remove any radiator caps. Remove the switch from the radiator and relatively quickly install the new switch. You will loose a little coolant, but because you have everything else capped and sealed, you won't loose much. Then, just top off the radiator.

[fenixus]

Originally Posted by 93celicaconv

No, Fenixus.

Your dash temperature gauge reads the temperature of the coolant as it exits the engine through the water oulet. It does not measure the temperature of the coolant in your radiator.

I wish I had a service manual for your car, but I don't. I do have a 93 Celica with the 5S-FE, and that car has 3 coolant sensors:

- one in the water outlet housing, a 1-wire sensor, that drives the dash temperature gauge
- one in the water outlet housing, a 2-wire sensor, that feeds coolant temperature information to the ECM
- one in the bottom tank of the radiator, that switches the radiator cooling fans on based on the coolant temperature in the cold tank of the radiator.

Because someone said there was a temperature switch in your radiator, I am assuming your Solara has a similar setuup to my Celica.

OK, got it now.

You did say you have an overheating problem, right? And that your radiator fans don't operate unless your A/C is on? If you have a sensor in your radiator, then your ECM doesn't control the fans on your radiator, so your ECT sensor doesn't have an effect on turning your radiator fans on or off. Now, if you don't have a temperature switch in your radiator, then we have a different story. But someone said you did.

uhmmm, never had the classic overheating problem when driver can observe dash needle going into red zone. it always sits right below half mark or at it once engine is warmed up.
radiator fans do kick in from time to time and operate fine i think (no A/c required for this). sorry i might have been unclear on this one.

my only concern are obd2 readings from my car that says engine coolant temp grows to 212-214 at idle in parking lot and that is when cooling fans kick in to beat it down to 203F. when driving this temp reading stays in 180's-190's F. however on all of above occasions the gauge needle in dash does not move even 1mm.

i would trust what Hill says about my car coolant sensors more than what i say hehe. i'm just a car hobbyist here and Hill is an experienced mechanic (am I right?).

so based on above i must have at least 1 bad temperature sensor as their outputs do not match with each other.
in end result ECU sees too high temp while it's cooler or dash gauge sees normal when it is otherwise.

considering that i have crazy fuel trims also then as suggested by Hill I also would point my finger at ECT sensor for EFI (ECU input). already ordered this one online.

[fenixus]

Originally Posted by hill8570

Nope -- like I said, dash gauge sensor is right next to the ECT, right where the upper radiator hose enters the engine. Temp switch for the fans is on the bottom passenger side of the radiator.



You don't have to drain coolant to replace the ECT, although you'll want a rag around the area to catch dribbles. If you replace the fan temperature switch on the radiator, yeah, you'll have to drain the radiator. Won't have to drain the block, 'tho.

thanks, i finally seem to understand it. good tip on removal, will cover with some rags around when replacing ECT sensor for EFI. do i need to use any thread lock paste when installing new one ?

i am not 100% sure temp switch in radiator is operating OK though, i suspect having at least 1 bad temp sensor, may be this one is acting too late allowing temp getting too high or so (but then why dash gauge does not see it?).
also when i touch radiator cap with my hand it's not even hot, it's barely warm.