3.2 Inputs 3 MS3PRO HARDWARE
If using the opto-isolated input, connect CKP+ to sensor ground to reduce possible noise issues.
Some spark modes, discussed in the ignition section of the manual, use the digital I/O channels as well. These
come into play for systems that either use very high frequency signals (such as the Nissan or Optispark optical
systems), require more than two sensors for engine position (such as the Audi “tri-tach” system), or use more than
one channel of variable valve timing.
3.2.2 Temperature inputs
The IAT and CLT inputs are designed to accept input from a negative temperature coefficient thermistor. Simply
put, this is a sensor that is a type of resistor that changes resistance with temperature, and the resistance goes
down as the temperature goes up. The default settings are for the sort of GM sensors that are something of an
industry standard in the EFI world, but you can calibrate it for other sensor types through TunerStudio. The voltage
on the sensor will decrease as the temperature goes up.
TunerStudio will ask for a bias resistor value when calibrating temperature sensors. This referes to a resistor
inside the MS3Pro and should be set to 2490 unless directions specifically say o use a different value.
A third temperature input monitors ECU internal temperature. This sensor cannot detect individual hot spots,
but if you are installing the MS3Pro under the hood or in other applications where you are concerned about
exceeding its internal temperature limit, this will let you log and view how hot the MS3Pro is getting.
3.2.3 Throttle position
This input can accept signals in the 0 to 5 volt range and will is compatible with almost any potentiometer type
TPS. If your engine does not have a suitable TPS, you should connect this input to the sensor return. Leaving this
input free disconnected can give a false high TPS reading and cause the MS3Pro to trigger flood clear mode when
starting.
3.2.4 O
2
sensor input
This input is also 0 to 5 volts. It can be used with either narrow band O
2
sensors or accept an analog output from
a wideband O
2
sensor controller. It will not interface directly with a wideband O
2
sensor, but it is compatible with
most external wideband controllers, such as Innovate, AEM, Zeitronix, PLX, and 14point7.
The general purpose analog inputs may also be configured as additional O
2
input channels and work in the
same way when set up as O
2
inputs.
Some devices allow you to bring the O
2
sensor input over the CAN connection. If using a CAN-based wideband
or not running any O
2
sensors, you can repurpose the O
2
input as a generic analog input to connect other devices.
3.2.5 MAP sensor input
The MS3Pro Ultimate has a built in 4 bar MAP sensor. Connect the MAP sensor hose barb to the intake manifold
downstream of the throttle body using a 1/8” ID hose. If you need to calibrate this sensor, it uses MPXH6400
calibration. If you prefer an external MAP sensor, you can use any unused analog input pin for MAP input.
3.2.6 General purpose analog inputs
These inputs can accept a 0 to 5 volt signal from a variety of sensors, which can be used for barometric correction,
additional O
2
sensors, voltage based MAF sensors, or simply for data logging additional sensors such as oil or fuel
pressure. If using these inputs with an external two wire temperature sensor, you will need to add a 2.49K resistor
as shown below.
AMP EFI MS3ProUltimate manual version 1.203, firmware 1.5.0, 5/23/2017 Page 25
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