We have an MXG installed in a Boxster S Race Car. We just did some transmission work and installed a bung for an NTC Temperature sensor (Bosch NTC M12 -40 to 130c temp sensor), however we are getting strange readings on the dash.

What we have done so far:

• Created a custom sensor based on the resistance/temp table for the sensor
• Wired the sensor to a AIM 719 plug to Pin 1 (Analog Signal) and Pin 2 (GND)
• We have tested the sensor and based on the resistance in the table the temp is correct
• We tested the wiring and the resistance at the 719 plug end is the same as what is read directly at the sensor end.
• We have pluged it in to 2 different analog inputs on the 37pin AIM wiring harness with the same result.
• The dash is reading 165 Degrees C, way beyond the range of the sensor and equates to 0 Ohms.

Basically what we have worked out is that the MXG is reading resistance of 0 Ohms and not the input coming in from the wiring.

Any help or guidance would be appreciated.

 

Your diagnostic train sounds good.

Primary harness to the MXG is in question for that channel.

Ping your dealer or AiM Sports in Roanoke or Lake Elsinore, California for additional support.

 

Thanks Peter, will connect with AIM.

 

What are you using for a pull up resistor?

 

The recommendation for the sensor is 1000 to 3000 Ohms, I have used both of these 2 limits and the recommended pullup of 2700 as per the RS3 Software.

 

Have you tried a different sensor on the same channels that are not working with the temp sensor? If those work, then it's a wiring problem.

Pull up resistor between vref and sensor wire,.other sensor wire to ground, correct?

 

I have brake pressure sensors that are working on Channel 1 and 2 so I can test on either of those 2 Channels.

That is a negative. I have Pins 1 and 2 connected to the sensor. (Analog Signal and Ground)

Am I supposed to also link Vref to Pin 1 via a resistor?

 

Yes, that is the pull up resistor. That converts the resistance to a voltage. The value you see on the custom sensor screen is what is used to calculate the voltage that results from the circuit.

It won't work until you add the pull up resistor.

 

Thank Matt, I will add a resistor to the circuit between Pin 1 and Pin 4.

 

Make sure you add the correct value resistor to match the calculations you did in the custom sensor menu.