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7 months and everything is still the same

This is going to be long I hope the answer isn’t. I own a 2001 toyota carolla S, 5 speed, air conditioning,

with 84,000 miles on it.

7 months ago my cooling fans quit working, since then I have changed all fuses, relays, temp sensor.

thermostat, water pump, head gasket (three times), radiator cap, Now I still have the same problem.

Oh, I put a new motor in it too, along with a new clutch, pressure plat and throw out bearing.

The car starts and remains on fast idel, the fans don’t come on unless I unplug the temp sensor, but if I shut the car off

it will not start until I plug the temp sensor back in

If anyone can fix this I would sell my next born child to them. lol


When you put the new motor in, did you also replace the ECU?


Did you ever check to see if the cooling fans are getting juice? Did you replace the cooling fans?

As I said, the fans work fine as long as the temp sensor isn’t plugged in,

If it’s plugged in the fans don’t work, the air conditioning doesn’t work and

it wants to idel at 1200 RPM. Unplugged, it wont start.

This is not a drive by quest, I have actually been working at this for seven months.

Where’s the borthers when ya need them?

Ok, I’ll keep looking back, but my next stop is going to have to be a dealer and

I trust them less than a carnival barker.

By unplugging the temp sensor, the engine is defaulting to a fail-safe protocol to turn on the fans. It sounds like you have a fault within the ECU. A scan tool that can read sensors can confirm this. Maybe the program has a bug, and re-flashing the ECU can fix this, bit you’re going to burn up this engine the way you’re going. A trip to a shop or a dealer would be cheaper than all the parts you’ve thrown at it so far.

Arf! Carnival barker here, you just added more information, ac not working and wants to idle @ 1200 rpm, any other symptoms?

BK, I have a scaning tool for it. Since I last talked it told me I have a bad temp sencor,

I plugged it back in, reset the codes and now the temp guage goes to hot when the key is turned on and the fans still don’t work unless they are unplugged

Oh, the check engine light is out, NO check engine light now.

But, does you’re scan tool read individual sensor feeds, or just check DTCs? If the ECU has a fault, DTCs can be misleading. It sounds like sensor feeds need to be looked at and evaluated to determine if there is an ECU fault.

This thing reads everything but the evening paper.

Can you see the CTS data stream as the car warms up? Does the data stream behave as expected?

Yes and yes.

This new motor is a 2004 1.8 with all the sensor from my 2001

eveything is jake except those $&# fans.

It’s probably designed so that if the temp sensor is accidentally unplugged, the fan will spin. That’s the way it works on my early 90’s Corolla. That’s a fail-safe mechanism. It’s better to have a too-cold engine than a too-hot one.

On my car, the fan spins when the engine main relay is “on”, and the fan relay is “on”. The fan relay is enabled (again, on my car) by the radiator fan temperature switch. The ECM isn’t involved. If that switch becomes enabled by the coolant temp, it will turn on the fan relay, and the fan will spin.

On newer cars, probably the case for a 2001 like yours, it works differently. The ECM reads the coolant temp and decides for itself to turn the fan “on” or “off”. It seems like the fan should start if the sensor remains unplugged and the car is started and the engine is running. I expect that’s a symptom of something being wrong.

I guess what I’d do in this situation is (1) bench test the coolant temp sensor that the ECM uses for this function. It should read a certain number of ohms, which change according to the temp. You’d put it in a pan of water and slowly heat it up and read the ohms vs temp. If it is working it will correspond to the specs for the part. (Which would be in the shop manual.)

If that tested out ok, I’d test the ECM signal that turns on the fan relay. It should turn on if the temp sensor is disconnected. If it is in fact turning on, but the fan isn’t turning on, that should prove easy to fix. It’s either a bad fan relay or a connection gone bad somewhere in between.

If the ECM isn’t turning the signal on, then either the wiring between the sensor is bad, or there’s a problem with the ECM. Either there’s a bad connection nor it needs to be replaced.

Another thing you can do is turn the AC on. That usually causes the radiator fan to spin too. Does the ECM send out the signal for the fan to spin when the AC is turned on?

Just noticed you are using a 2001 sensor with a 2004 motor. That could be a problem. Go to the parts store and ask to see the ECS (engine coolant sensor for the computer) from both cars. Do they look the same and are they the same part #? If not, that is likely the problem.

He says the ac does not work, here in his quote I think lies the problem.
“This new motor is a 2004 1.8 with all the sensor from my 2001”

The set-up should be fine. The ECU and wire harness is also 2001, so the 2001 sensors should be the right ones. The key here is the fan problem. If I read the original post correctly, the fan problem pre-dates the 2004 engine swap. With all the work done up to now, the ECU is the next logical suspect.

However, you can by-pass the ECU fan control by re-wiring the fan relays to come on with the ignition. I’ve done that before with an old beater car to keep it running.

you can by-pass the ECU fan control by re-wiring the fan relays to come on with the ignition. I’ve done that before with an old beater car to keep it running.

How would I go about doing that?

I am 70 years young and have done my own car repairs for the last 53 years.

I do not like paying someone 65 dollars an hour for something I can do.

Oh, I was just looking at ECM on the webs, $235.00 don’t sound that bad

to me, right now and I know how to take the old one out.

As I told someone on another topic, I love this car and have wished to have back

many that I have owned before, I wont do it with this one, even if it takes every

cent I can get my hands on.