Aem EMS 2 and Coolant Temp Sensor

[JFC3000GT]

Hello everyone,

I was wondering if anyone had any problems with the stock calibration that comes with the aem ems 2. I'm using ver. 01v24. My car overheats because the the temp stays to low for the fans to come on. The stock guage is pegged but the aem says the temp is only ~140F?. I have checked the voltage coming out of the sensor and it matches what aem tuner says. i have no idea, maybe a bad ems?? :scratch:

[vr4tune]

Is you car a 91-92? I use the stock sensor for the ems.

[DuTTch]

I am somehwat in the same boat,however my fans are on 24/7 coolant temp sensor just wont work upgraded all the software and firmware,I switched out a stocksensor to an aem coolant sensor and still no luck. When car gets hotI cant even connect to aem anymore sotommorrow I am gonna get a troubleticket and I want tosens it in to aem. I am sofrustrated with this.

[vr4tune]

DuTTch series 1or2

[mb3000]

IIRC there is a gauge sensor and an ecu sensor. For 91-92 there are additional sensors as the fans are controlled separately from the ems.

[DuTTch]

DuTTch series 1or2

american series V2 lol,

[JFC3000GT]

Vr4tune- my car is a '94

I also bought a brand new coolant sensor thinking maybe the original was bad and also no luck.

I put the stock ecu back on and checked the temp using the hhh datalogger, then using multimeter i verified the voltage coming out. I did a new coolant sensor calibration on aem tuner using those values and still no luck!! The temp on aem tuner still registers too low. At this point i'm thinking of giving aem a call.

[Intropy]

Hello everyone,

I was wondering if anyone had any problems with the stock calibration that comes with the aem ems 2. I'm using ver. 01v24. My car overheats because the the temp stays to low for the fans to come on. The stock guage is pegged but the aem says the temp is only ~140F?. I have checked the voltage coming out of the sensor and it matches what aem tuner says. i have no idea, maybe a bad ems?? :scratch:

Set your Rad Fan 1 & 2 options so that the fans are on all the time while you troubleshoot.

Basics - test the sensor, then test the wiring. For the sensor, immerse it in water and check the resistance. Then check the resistance of the wiring.

[Intropy]

Oops you posted while I was composing.


i verified the voltage coming out. I did a new coolant sensor calibration on aem tuner using those values and still no luck!! The temp on aem tuner still registers too low. At this point i'm thinking of giving aem a call.

Wait, what? You're saying that no matter what the Coolant Sensor Cal is set to, the Coolant Temp channel stays the same? If you go to Coolant Sensor Cal, hit 'Ctrl-A' then 's' then type '210', what does Coolant Temp say?

[JFC3000GT]

Oops you posted while I was composing.



Wait, what? You're saying that no matter what the Coolant Sensor Cal is set to, the Coolant Temp channel stays the same? If you go to Coolant Sensor Cal, hit 'Ctrl-A' then 's' then type '210', what does Coolant Temp say?

Sorry Intropy, what i meant was that even if i plugged the values taken from the stock ecu( Used hhh for temp ref and multimeter for voltage) into the coolant sensor cal the stock gauge still pegs way before the fans come on. Same thing on the stock cal on the ems. You have the ver2 did you have any problems?

[Intropy]

No but I don't use the stock coolant temp sensor. Anyway, if you don't want to chase your tail forever (and want to have all your facts straight if you actually need to contact AEM):

Put a pot of water on the stove with a thermometer. Using ice and heat, measure the resistance of the sensor at various points. What you should see is a roughly linear inverse relationship between temp and resistance (high temp = low resistance, low temp = high resistance). If you don't see that over the full range of operating temps, the sensor is not suitable for use with the EMS.

Now build you Coolant Temp Sensor Cal table. Take the resistances you measured and apply the formula:

V = 5 * ( x / ( x + 2200))

E.g. if you measured 2000 ohms @ 80 degrees F, then V = 5 * (2000 / (2000 + 2200)) = 2.38V. So on your cal, you would put 80 degrees F for 2.3V.

At that point, you have a known-working sensor and a good calibration. The last thing you need to check is that your harness is OK. Make sure the resistance is near zero.

Now hook everything up and connect to the EMS (car cold, not running). Presumably your coolant temp is near ambient. Make sure that's reflected in AEMTuner.

Now go to Display -> Show Options and set "Rad Fan 1/2 Off Below" to the lowest possible value "Rad Fan 1/2 On Above" to one degree higher than that.

Then start the car and make sure everything looks kosher. If not, you've done your homework and you probably have an EMS problem.

[Intropy]

No but I don't use the stock coolant temp sensor

Actually I take that back, on my TD04 car I do.

[JFC3000GT]

No but I don't use the stock coolant temp sensor. Anyway, if you don't want to chase your tail forever (and want to have all your facts straight if you actually need to contact AEM):

Put a pot of water on the stove with a thermometer. Using ice and heat, measure the resistance of the sensor at various points. What you should see is a roughly linear inverse relationship between temp and resistance (high temp = low resistance, low temp = high resistance). If you don't see that over the full range of operating temps, the sensor is not suitable for use with the EMS.

Now build you Coolant Temp Sensor Cal table. Take the resistances you measured and apply the formula:

V = 5 * ( x / ( x + 2200))

E.g. if you measured 2000 ohms @ 80 degrees F, then V = 5 * (2000 / (2000 + 2200)) = 2.38V. So on your cal, you would put 80 degrees F for 2.3V.

At that point, you have a known-working sensor and a good calibration. The last thing you need to check is that your harness is OK. Make sure the resistance is near zero.

Now hook everything up and connect to the EMS (car cold, not running). Presumably your coolant temp is near ambient. Make sure that's reflected in AEMTuner.

Now go to Display -> Show Options and set "Rad Fan 1/2 Off Below" to the lowest possible value "Rad Fan 1/2 On Above" to one degree higher than that.

Then start the car and make sure everything looks kosher. If not, you've done your homework and you probably have an EMS problem.

Thank you, I will try this out and see if it works properly!

[JFC3000GT]

hello everyone, quick update i re-did the calibration with the values i got from doing intropy's coolant sensor test and it's working fine now. The fans are coming on on-time and the temp values are good. Now on to getting my car tuned!!!

[mb3000]

Great! Good luck with the tuning!

[JFC3000GT]

Great! Good luck with the tuning!
Thanks! i can't wait to see how much i make with DR750R's :DevilSmile:

[DuTTch]

well my aem ems is at aem tech for further examaniation