GPI1 needed for a 2wd application?

[12lbchevelle]

Is the GPI1 circuit needed if the vehicle is strictly 2wd?

Thanks,
Dan

[Bernard Fife]

Dan,

If you don't need GPI1 for 2WD/4WD switching, or use as the 4th input, you don't need to install all of this circuit. However, you should hold the pin high by installing R21 and R27 (if you don't have the exact components handy, any value between 330 and 10K Ohms will work for both). Then be sure not to ground the connected wire on Ampseal pin #5 - it might be a good idea to cut this and seal it in the harness, just in case.

Lance.

[12lbchevelle]

Thanks Lance,

What might one use the "4th input" for?

[Bernard Fife]

Dan,

The 4th input is used if your trans has 4 digital signals to indicate the gear lever position. The 4L60E and 4L80E only have three digital signals, so they don't use this. The Ford trans typically have a variable voltage based signal, so they don't use it either. But some other transmissions might use it, so it is there.

There is more on this here: http://www.msgpio.com/manuals/mshift/V2tune.html#gi under 'GPI1/Amp5 INPUT Usage'.

There are two settings:
Additional gear lever input (In4_cfg): "Speedo Switch/Logging", "Additional Lever Input"
2/4WD input usage (FWD_cfg): "Log only", "Use to switch speedo"
(these are both bits of the stdin_cfg byte parameter, bit 0 and bit 3 respectively)

Note that if you tie the input high (as suggested above), you should leave these at the default settings in bold above.

However, you can log a digital 0-5V signal with this input, if you like (its not all that useful, though - it will only log whether the signal is a logic 'high' or 'low'). Under 'Standard Inputs/Outputs Configuration', set '2/4WD input usage' to 'Log Only', and 'Additional gear lever input' to 'Speedo Switch/Logging'

Lance.