MFI Schematic - I/O

This page is a collection of notes on how to read certain information off the MFI schematic in the DSM shop manual. First, reference the 2G MFI schematic (or the 1G MFI schematic) for an example of what this schematic looks like.

This is a simple analog (0-5v) input to the ECU. No significant load on the sensor is illustrated in this diagram. When nothing is connected to this input, the ECU will see an undefined value. It could be just about anything from 0-5v.

This is a 0-5v input to the ECU but with a pull down through some resistor. The implication here is that any voltage source (sensor) connected to this input will be expected to drive the load of that pull down. Some sensors simply can not do this. You can get more info on our ECU Input Data page.

When nothing is connected to this input, the ECU is going to “see” ground (0v).

This is a 0-5v input to the ECU but with a pull up to 5v through some resistor. Which means when nothing is connected to this analog input, the ECU is going to “see” +5v.

This is a 0-5v input to the ECU but with a pull down to ground and a pull up to +5v through some resistor combination. The implication here is that any voltage source (sensor) connected to this input will be expected to drive the load of that pull down. Some sensors simply can not do this. You can get more info on our ECU Input Data page.

An example of this type of input would be a temperature sensor. Thermistors require this type of drive circuit.

This is a digital input to the ECU. The default “value” seen by the ECU for this input is +5v (when nothing is connected to the input or when the device connected to that input is simply “inactive”). When the input is “active”, the external device is expected to pull this signal to ground, which will cause the ECU to no longer see the +5v value and instead see ground reference through the transistor.

This is a digital output from the ECU. When it's “active”, the output will be switched to ground (low-current sensor ground!). When the output is “inactive”, it will be connected to nothing (floating).