Ford Auto trans details

[DMX]

how's this? I'm not sure where the Vref comes from i'll have to look more closely when I get home

[Bernard Fife]

DMX,

This is very helpful, it is quite clear (and the text boxes help). It looks like the voltage source for the divider comes from the trans (GY/R wire) and the resultant voltage is sent to the PCM on the LB/Y wire. If anyone has a pic of this switch, that would be great. What I am particularly interested ion knowing is whether the main connector supplies the voltage to the switch or not (i.e., does MegaShift need to supply that voltage, or does it come from the harness...). To me it looks like the supply votlage is part of the harness, since the VSS and engine controls use the same source. I guess if we knew what the connectors looked like we'd know...

Lance.

[devojet]

From what I can tell from the Ford falcon diagrams is the switch sensor has two wires, Ground and Signal so I would assume the pull up is in the ECU.

In the above diagram my guess would be that point A on the GY/R wire is some form of ground connection to the gearbox.

[DMX]

A few more docs, i'm not sure what you guys mean by the pullup. I interpret [199 LB/Y] as +5v vref, apply that voltage along different points in the stacked resistor voltage divider to produce a 0-5v signal in [359 GY/R], this then makes it way back to the PCM as sig rtn. I might be overlooking something obvious though.

AX4S TRS analog voltage.jpg (120.19 KiB) Viewed 16272 times

mlps3.jpg (155.82 KiB) Viewed 16274 times

ax4s trans.jpg (137.6 KiB) Viewed 16271 times

[Bernard Fife]

DMX, devojet;

Okay, so MShift will supply the Vref through connector C168 (my concern was that if the existing 5V is supplied in the harness in a manner that is difficult to disable because it doesn't terminate at one of the transmission connectors, but fed in somewhere else - in which case we'd likely have to use the existing supply). Thanks for all the info, this is great!

Lance.

[devojet]

Hi Lance,

That sounds fine to me. As long as the code can read the voltage ranges from the gear selector I have no problems sorting out the hardware.

I'm also thinking I will use this input for my toyota gearbox as it just has a switch with a position for each selector position. Buy adding a few resistors I should be able to make it work like a ford switch which will be easier than mutiplexing it with transistors and diodes to look like the 4l60E pressure switch inputs. Plus this way I will free up 2 io pins.

Cheers

Daniel.

[Bernard Fife]

Daniel,

I'm thinking we ought to be able to have either the voltages or the resistances as parameters in MegaTune, then the code can convert these to ADC counts and compare to the measured value to find the current gear (with software debounce, of course). Then we *should* be able to make one code work for lots of transmissions with no hardware changes.

Lance.

[devojet]

That should suit most people including myself.

Cheers

Daniel.

[Bernard Fife]

All,

A question (I have owned a lot of older Ford's, but the most recent was built by Mazda and has a manual trans): I see the manual gear lever positions for P-R-N-D-2-1. Is D for both 3rd and 4th gear? Then 2 and 1 manually select second/first or first gear? Is a bit of a silly question, but I'm writing the code and want to make sure to get this right (for example, my Toyota has PRND21, but D is 3rd and the overdrive (4th) is a separate button at the end of the shift lever).

Lance.

[devojet]

Hi Lance, My Toyota is the same as yours, but my Ford BTR gearbox has PRND321.

What would be handy is the inputs from the selector switch and then a selectable OD switch input for cars like the toyota.

Cheers

Daniel.

PS when I get a chance I will put the Toyota info I have into the toyota thread I started a long time ago.