Hi i have a 2005 scion tc with 120k just bought the car and noticed the radiator and condensor fans not coming on follwed toyota's wiring diagram but i am undecided if its the ecu or the a/c amplifier?? any one heard of this problem or something simiar?? what was your repair?? thank you!!

 

i haven't seen anything like that.. but I did just look at the service manual and it says
"Check that the cooling fan rotates.
If not, check the fuses, cooling fan relays, ECM and cooling fan,
then check for a short circuit between the cooling fan relay and
engine coolant temperature sensor"

so looks like start simple, fuses, then the relays, then apply 12v to the fan see if it even spins. haven't had a lot of the ecm's die on the tC, it's usually a simple fix. ok.. keep us posted

 

ok ive already checked all fuses, relays, and applyed 12v to fan w/ power probe i comes on have no power at the fan termincal and when i just the coolant temp sensor have no effect so with that done and said i am starting to think its an ecm what you think?? and its hard for me to say that as a former toyota dealership technician because this car is equipped with a denso ecu and the problem is that the ecm controls the fan opperation

 

https://na.tis.toyota.com/t3Portal/r...&context=natis this is the official toyota EWD

 

Something i just realized that now has me going crazy is why is fan relay #3 only 4 wires on the EWD but has a 5 prong relay?

 

More information needed

Is your engine even getting hot enough to turn the fans on? Just because you're at temperature doesn't mean the fans will come on. I can't find the actual temperature for the tC but the xB is set for 205F with an operating temperature of 185F. I do know my tC runs 185F under normal operation and will get to 200F at stop lights. I also have a turbo sitting right behind the radiator so I probably run a little hotter than stock.

Oh and don't get bent about the relay. Manufactures will buy one part and use it through out the car even if they don't fully utilize it. In the long run it saves money.

 

I was going to question if it was hot enough for the fans, but he said he tested them? It's hard to take these threads seriously (no offense to OP) because many people think the fans kick on with the car.

 

Yes the engine is hot enough for the fans to kick on it even over heats

 

Yeah i applied direct power to them and they kick on the engine does get hot enough for them to kick on there is just no power getting to them they both have proper ground!

 

as stated above, did you check temp sensor? does it work?, does it need to be cleaned? has the maintnance been done to radiator fluid?, did the thermostat stick shut? ecm is out of your question.

 

This is not meant to insult but to gather more information.

How do you know it's overheating? Are you going by the gauge on the dash or by steam coming out of the hood or something else? Is it overheating at stoplights and is fine going down the road or is it straight overheating? Anytime someone tell me that an engine is overheating I want to know why. From what I can tell the fans should never come on anyways so if your ride is overheating I do believe you got more than just bad circuit going on.

Ok this one has made me do a little research. One, the fans should come one at low speed even with the engine cool if you push the AC button. It's currently 45F here and I just went out to my tC and it did come on so lets start with that. So AC button on and fans don't turn on. Relays and fuses test good. First thing I would do is check if your getting power to the AC Condenser fan motor. Understand this has to be check with the engine running, just turning the car on or ECM will not engage the FAN No 3 Relay (should be able to just pull the connection and do a volt check). If you got power there then that means that the ECM is working and you just have a brake in the power line for the fans that needs to be fixed. Troubleshoot the lines from there. If there is no power at the AC Condensor fan motor I would first check to make sure there was power both to and from the Fan No 3 relay (terminal 5 in and 3 out) and there was no power coming out then Check D5 Diode. If the diode checks out ok then see if your getting power to terminal 2 of the ECM If you are then it could be the ECM. Too rule out the AC Control Assembly check to see if you have power at Pin 30 of the ECM. As I'm not sure if there is suppose to be a signal there or not, I would check Pin 30 both with the AC button activated and deactivated but my guess is that it should send a signal when activated and no signal when deactivated (based on the light on the switch). If you get a change in state their then the AC control assembly does work and the problem is likely the ECM. No change in state then it's either the AC control assembly or the line running to it.

How you check at the pins I leave up to you. I've got enough work to do to get my car ready for the test and tune next week and really don't feel like digging into that detail but that should give you a pretty good idea of where the problem lies. I still think you got another problem if your car is overheating but that's another matter.

Oh and sorry about the wall-o-text.

 

Actually the ECM is not out of the question as the Engine Coolant Temp Sensor, the AC Control Assembly and all three FAN relays are controlled in some way by the ECM.

One last thing to the OP. What I posted earlier was just for the low speed, there is a high speed connection system as well but what I put up there should tell you if it's the ECM or not. It the problem is the fans will kick in low but not high then I make sure I check the P5 Pressure SW.

And for those that don't know https://www.scionlife.com/forums/scion-tc-1g-ice-interior-1647/scion-tc-electrical-wiring-manuals-05-07-a-73323/

It's page 170-173 in the 05 manual.

 

If direct power is making them work, and you claim they don't work when the engine is on, you're looking at relay or a short in the power wire somewhere in line. But, I'm interested to know how you know the engine is at operating temperature. It doesn't sound from your description that the car is actually overheating at all.

 

ok i started the car and had it running for about 30-45 min + or - and once the neddle reached the red line on the temp guage checked the upper and lower radiator hoses got 227f at the lower and 224 at the upper so with that said it rules out the thermostat operation! as Esh Darkstar stated i checked pin 2 (brown wire) then checked pin 30 (pink wire) and had no signal so with that being said i think im going to start with a a/c amplifier (a/c control panel) ill be picking up a used on tomorrow monday (2/13/2012) drop it in and then ill post up results. im pretty sure its gona be the a/c amplifier as i remeber seeing this problem once when i was working as a tech at toyota but i dont remeber if it was the exact same problem! Well i wana thank everyone that has helped out so far and ill check back in tomorrow with new results hopefully i can get the car back on the road!

 

Uh, there are a lot of things wrong here.

Ok it's taking between 30 and 45 minutes to get it up to red line? Taking that long definitely rules out the the thermostat. I'm starting to think you probably need to check the radiator, I think it might be partially clogged and here is why. The fans have two modes. The first being low speed which is controlled by the AC amp via the ECM, and the second being high speed. High speed can be initiated by two methods, one through the ECM monitoring the temperature and the other by the pressure switch. Now since the car when running does neither low or high speed that means the ECM is not letting the current path for the fan relays to be completed so the fans will not engaged. From that stand point you need to check to make sure ALL grounds are connected properly on the ECM. Thing is I said there is two ways the high speed can be engaged, the other is through the P5 pressure switch. Once the pressure gets to a certain point on the radiator it activates and turns on the fans to high. This is independent of the ECM and I would imagine that it should happen before red line. Now if the radiator is partially clogged (why you don't over heat immediately but eventually) it is quite possible that this switch is also clogged up. I would pull this plug (hot or cold it won't matter) and jumper the pins to see if the fan turns turn on. My money is on that they do since I think the radiator is partially clogged but if they don't then you know the problem is that the relays are not working.

 

i forgot to mention it was about 40 something degree when i tested it so thats why it took a bit to get up there, ive already tried jumping it but nothing happens but again gota remember the coolant temp sensor sends a signal to the ecm then the ecm snd the signal to the relays i physically tested each relay and the are working properly

 

Er, yes and no. The ECM doesn't send a signal per say, what it does is it completes the path to ground so that the coils on the relays can activate. Right now the ECM is not doing that. I'm also wondering why the P5 is now working as a fail-safe as shown in the drawings.

You should not over heat at 40F, period. I went out to my tC last night to see how hot it would get at idle. We were at about 35F here in North Carolina so very similar temps. I got to 165F max at idle. To get it to 180F I had to rev the engine to 3K RPM for several minutes and when I brought it back down to idle the temp dropped back down to 165F in a couple minutes. The fans never cut on. Now my numbers might be slightly off as I'm using the Torque App and not an actual Toyota Diagnostic tool but the gauge on the dashboard also confirmed the rise and fall in temperatures.

 

40 mins at 40 degrees? Wow.

 

ok after installing a known good a/c amplifier had no change! So now im pretty confident its the ecm! but now i got a good question how do i program the imobilizer with the new ecm w/o having to take it into the dealer?

 

search "paperclip", easy swap also. i changed mine from 07 to a 2009, due to the fuel and throttle delay.