Simple rules for using the original ECT module on cars other than the S2000:

1. The "AEM" version of the ECT module is ONLY for those using the AEM-EMS system.

2. If you have a Civic, chances are the "ECT-2" module will work for you.  From customer feedback I'd say 75% of Civics will work without the need for custom programming.  Just make sure you get the right ECT module (AP1 or AP2) to match your S2000 cluster.

3. If you have something other than a Civic, you have maybe a 50/50 chance of the "ECT-2" module working.  You are probably better off using the "ECT-2S" (with calibrated sensor) or the "ECT-A" (adjustable).  A third option is to buy one of the "Custom" versions where you make a few measurements with a multi-meter and I pre-program the ECT module for your particular car. I suggest you follow this procedure to verify your car is compatible.  The other advantage of making these measurements is that if your car needs a specially-programmed ECT module these tests will give us the data to do the programming.

4. If you need custom programming, either before or after you buy an ECT module from us, you can do the programming yourself if you have a Windows XP computer with a serial port.  If you don't, we will be happy to re-program the module for you at no charge - you only have to ship it back along with your test measurements.  We'll program it and ship it to you at no additional charge.

5. Remember that all Modifry Products come with a 30-day return policy.  If you return the item within 30 days we give a full refund of the purchase price (less shipping).  Even if it has been installed, wires cut, etc, that is not a problem.

Answers to some frequently asked questions:

Should I buy the "stock" or "AEM" ECT module?

If you are using the AEM EMS get the AEM version, otherwise get the stock ECT module.  The only difference is the initial programming that I load into the module to save time for S2000 owners, but since you don't have an S2000 there is a good chance that no matter which module you get you'll have to re-program it for best accuracy.

Should I buy the AP1 or AP2 module -  

That depends on which instrument cluster you are using.

There are two versions of the S2000 gauge cluster, named AP1 and AP2.  AP1 refers to years 2000 to 2003 and AP2 is years 2004 and 2005.  You must use the correct ECT module for the cluster you have.  Using the wrong ECT module will cause the gauge to read incorrectly, and this cannot be fixed by loading new values into the module - you will have to change the ECT module.

What if my fan switch is different or I have "manual" fans?

That won't matter, as the ECT module gets wired to the "other" temperature sensor, the one that connects to the ECU.  This other sensor is the one that helps the ECU determine how much fuel to inject or how to set the ignition timing so it is a separate sensor from the fan switch.

AP1 Clusters (S2000 years 2000-2003) Tach redline is at 8900 rpm

The AP1 temperature gauge has 7 segments arranged in a horizontal bar graph.  The first segment is not active, meaning it's always on no matter what the coolant temperature.  The next 5 segments are yellow and the last one (the 6th active segment) is red, and these 6 segments will progressively light up to indicate coolant temperature.

To make the best use of the limited number of gauge segments I designed the AP1 module to have a lower temperature limit of about 160°F when used in an S2000, which corresponds to an ECT sensor voltage of 0.978 volts.  In actuality the AP1 ECT module can work with voltages up to .999 volts, which is a tad below 160°.  As the temperature increases the voltage drops, so this module can display temperatures of 160° or above (on an S2000), which correlates to sensor voltages between 0.250 and 0.999 volts.  If you are using an AP1 cluster and your ECT sensor voltage is in this range for normal engine temperatures then the ECT module will work in your car, though it may require re-calibration.

AP2 clusters (S2000 years 2004 and 2005) Tach redline is at 8000 rpm

The AP2 temperature gauge has 20 segments arranged in a 180° circular sweep.  The first segment is not active, meaning it's always on no matter what the coolant temperature.  The next 19 segments are the active segments that will progressively light up to indicate increasing coolant temperature.

Since this gauge has more resolution (more segments) I designed the AP2 module with a lower temperature limit of about 110°F (when used in an S2000), which corresponds to an ECT sensor voltage of 1.944 volts.  As with the AP1 module, higher temperatures are indicated by lower voltages, so this module can display temperatures of 110° or above (on an S2000). 

Special note to AEM EMS owners:

Some customers have had difficulty getting the gauge to display properly on AEM EMS systems.  I know of at least two cases where, after some troubleshooting, customers verified the voltage on the ECT sensor wire would change when other electrical loads turned on and off.  Sometimes the change was only 50 or 60 millivolts, sometimes several hundred millivolts.  In particular the radiator fan and AC system seem to cause the ECT voltage to fluctuate, and that of course makes the gauge display fluctuate too.

These symptoms are classic examples of a "ground loop".  Ground loops occur when current for one electrical circuit inadvertently flows through the ground leg of another circuit.  Here's an extreme example (if you have an S2000): pull the fuse for one of your HID headlights (low beam), then turn ON the low beam lights and check out the front of the car.  Not what you expected, huh? 

You probably figured one light would work and the other would remain off.  But in fact you will see one light come on normally, the other HID will flicker, and both high beams will be lit dimly.  This is how a ground loop works.  Power from the working low beam circuit back-flows through the high beam filaments and makes it's way to the low beam with the missing fuse.  Because current passes through both high beams and the HID (one big series circuit) they each get less than 12v, causing the high beams to glow faintly and the HID to flicker.  Cool.

With the ECT sensor, it's a similar effect.  If the sensor ground wiring is not exactly perfect, ground current for other devices will flow in the sensor ground wire, causing a voltage change that the ECT module (and the EMS too) will interpret as a different temperature.  How does ground current get into the sensor ground?  Think about it - how does ground current get anywhere in a car?  It flows through the chassis.  We think of the chassis as "one big ground lug" but in fact it's "one big resistor".  OK, it's a resistor with very low resistance, but when you pass a large current through even a low-ohm resistor you will get a noticeable voltage drop.

So the question is - did you move ANY ground wires in your car?  Did you remove or re-route any wiring to the engine block?  Did you move a ground lug or terminal from one bolt to another one "close by"? Did you move the ECM and use a new ground for it? Did you ground the ECT module anywhere other than directly at the ECM or at the ECM sensor ground?

Since the ECT sensor operates with very small voltages, even that "close by" ground bolt might not be close enough to maintain the ground integrity of the sensor wiring.  If there's only 1/100 of an ohm resistance between the two chassis points (original ground point and your new one), the radiator fan current (30-40 amps) could cause 300-400 millivolts change in the ECT voltage.  That 0.3 volts won't affect the radiator fan, but will surely screw up the ECT reading, as it can make the difference between a reading of 190° and 235°!

The bottom line: If you have ECT gauge problems, the first thing to do is put a meter on the ECT sensor wire and measure the voltage.  Look it up in the voltage/temperature table in the manual to see if it's in the range it should be.  Turn everything electrical ON and OFF and see if the sensor voltage changes.  It shouldn't change by more than a few millivolts no matter what is turned ON or OFF.  If it makes any sudden changes with electrical activity, then you've got a ground loop.