So it's not really a 20hp gain, it's a tool to prevent losing 20hp right? If it only prevents the car from going in 'safe mode' then it doesn't really add power, just prevents safe mode.


So far, there's no way I would trust my motor with letting the temps get out of hand. BTW, the dash coolant gauge is terrible and not to be trusted.

 

If you disconnect the Coolant temp sensor while key on or engine running, the fans will start running. I get a -40 F reading on the scan tool and throws a P0115 ....coolant input high.
My guess is if you have this chip, your fan won't turn on cause it won't see 190 F . But the ECU will think your still in the sweet spot so it will run maximun timing.

I tried measuring any Voltage but I get nothing.

An open circuit would give me an open reading. ( OL )

I have an extra conector in-line with the stock one and spliced it open so I can check what it is reading. Also have a scan tool so I see what the ECU is seeing.

Looked at the wiring diagram and one wire is ground and one is input. Both going to the ecu. The coolant sensor is a thermistor and puts out reistance and changes as temperature change. The ecu then converts it to degrees/celcius.

 

Judging what you desribe it look like one side of the sensor is connected to ground and the other side is pull-up to 5V via a resistor (this is the side that goes to the ECU). Do you know what the pull-up resistor is? Can you share the wiring diagram for the coolant sensor if you have it? This is not the same as the wiring diagram for the Fan control module.

The ECU cannot read resistance. The resistance changes so in term the voltage to the ECU changes as well. WHat you need to do is connect the sensor and put a volt meter across the sensor and measure the voltage at which the fan turns on and note the temperature. From this voltage and knowing the pull-up resistor value along with the pull-up voltage you can calculate what the minimum required resistor need to be for the ECU not to turn on the fan.

The ECU will throw a DTC if you disconnect the sensor because now the 5V pull-up will be directly feed to the ECU which triggers an open circuit. If the sensor is shorted to gnd or battery it will also throw a DTC. Bascially how it works is that under normal condition the sensor is connected and changes resistance with temperature which gives a set range of voltage that is consider normal. Anything above the normal voltages it throws a DTC. Keep in mind that the ECU maybe looking at other factors ( AC/Switch, Vehicle Speed Sensor) along with the engine coolant sensor voltage in order to be happy or else it will throw a DTC for fail safe reasons. SOunds complicated but simple.

I'm not sure what Dave is doing but it should something similar to what I just explain. Not sure what DTC he's throwing either.


I'm assuming:

5-13V = open circuit or sensor short to battery fault (I'm guess it is set to turn fan on under this condition. Rather have it on then always off and overheat the engine)

0-1V = short to gnd fault. (I'm guess it is set to turn fan on under this condition. Rather have it on then always off and overheat the engine)

2-4V = valid range

5V = -40 F
0V = 215 F

 

OKay found it. Sensor is being pull-up to 5V via a resistor. The other end goes to gnd. Wish they gave the pull-up resistor value. It looks like a 140 ohm 25 watt resistor (150F) should work fine. A 50W would be better

http://tinypic.com/bijg1t.jpg

http://tinypic.com/bijjuv.jpg

 

Great analysis Gokou.

Although I tried this in an effort to get a voltage reading with the connector plugged in and it still reads 0 . Even when the temp rise to 190 F and the fans turn on. NADA.

Your diagram is showing the 5v pull-up is in the ECU. Only way I see to get a voltage reading is opening it. I don't think I'm going to though.

Tommorow I'll jump the connector with a 5M ohm resistor ( since I read 5.2 M at 180 F ) and see what the ECU reads, temp wise.

 

nice work guys, let us know how the testing goes... anybody have this mod? Does the fan stay on or not?

 

Strange. Trying reading from the sensor input side to any gnd and see if it makes a difference.

Yes the 5V pull-up is in the ECU and do not open the ECU. You wouldn't be able to find it without a schematic of the ECU and it can be well hidden.

I don't think 5M ohm is going to work because it's too big but you can try. Thermistor is typically not in the M ohm range. My guess is that a 5M ohm resistor will trip the same DTC as if you unplug the sensor.

I would suggest trying a 140 ohm 25 watt resistor as well. You can also try a potentiometer so you can vary the resistance.

Good luck.

 

As I stated, I did that. No go. I now know what buschur's is (even the value), it would be very easy as a matter of a fact to make it, but I want to make something that doesn't shift the whole scale and you can leave it in. Gonna make it so you can clamp the voltage for ~180 degrees (.55volts)

BTW: for those of you interested, you can look HERE for more info and diagrams. Start @ about post #40, where I start the convo about this mod.

and, keep us updated!!

 

Got testing done today and here it is...

Your right Gokou, All my reading were off when I first tested it beacause I was working with a bad meter.
Got a good Fluke meter out and here are the true results:

200 ohms = 207 F
247 ohms = 190 F
277 ohms = 185 F
307 ohms = 180 F
400 ohms = 162 F

These are the reading I got from the ECU when I jump the coolant temp sensor connector.
I also started it cold ( 88.9 F ) with the 307 ohm resistor and it did not like it. I guess the ecu is seeing closed loop instead of open loop at start-up because of the reading it's getting ( 180 F ).
I'll try this at the tracks with/without this mod and see the difference between them.

Warning: User beware.
This mod will not turn your fans on so you will overheat if you idle it too long. Should not be street driven.
Put this mod in before you turn the ignition on. If your leave the ign. on while disconnecting the coolant temp connector to put this mod in. Fans will turn on and Check engine light will stay on. Either you pull the 15 amp engine fuse out or disconnect the battery to clear this code.
So there it is. You guys can add or subtract X amount of ohms to get the reading you want. I'll stick with the 307 ohm for 180 F.

Let me know what kind of results you guys get.

 

Great job glad you got it working. Did you jump or did you replace the coolant temp sensor with a 307 ohm? So the fan will not turn on and there's no cel correct. Was the whole purpose not to turn the fan ON or was the purpose not to have the coolant temperature over 180 C which will cuse the ECU to run the A/F rich. The reason I'm asking is that if all you care about is the temperature what you can do is hook up a switch to battery to the FAN and you manually turn the FAN ON while you have 307 ohm across the sensor

 

The coolant temp sensor would still be in there. I just un-plugged the connector and jumped the resistor across it so the ecu will read 180 F al the time.
The purpuse for this is to fool the ecu to not enrich the mixture as temps rise. I heard that the sweet spot is 170 - 190 F. It just so happens that the fan turns on at 190 F as I tested it.
If you want the fan to turn on after a run for cool down. Just leave the key in the on position and take the resistor off. This will turn the fans on. You will be left with a code though so just clear it before the next run. A switch would be very conveinient.

 

wat would be nice and convinient is somehow rig up a switch so u can do this from the cabin .. or something along those lines..

 

Cool! With the switch you can leave the resistor in and have the fan on at the same time

 

here's what I'm thinking so that you can have the fan run reliably while using this mod.... someone correct me if/where I'm wrong.


a.)how can I consolodate the two manual switches into one switch?
b.)how can I source the switch to activate the fan? Can I just get it off any older car that still uses one? How would I ensure that my thermistor readouts will correlate w/ my switch input?

 

Or you could just turn on you a/c, fans automaticly turn on.