EFIDynoTuning Forum

He actually replied shortly after. He said his solution wouldn't actually drive the tach, but from his description, it sounds like it might be able to be used to drive the tach input on the SGI-100BT, and then that drive the actual tach.

I had looked up the MPC-19D because that's the hardware I've seen in my searches, but that's not listed.

From your previous comment about moving the fan pins and making a change in the tune, I'm assuming 'although these ecus can run FBGI0 tunes these ecus physically do not have both fan outputs nor a starter interrupt output if not used factory equipped in the ecu' refers to just loading a FBGI0 based tune in and nothing else?

correct, you would need to move the two fan pins to unused output pins and then reassign them

i'll see if i still have the tach circuitry details, its probably from 15+ years ago with the whole rossion thing if memory serves.

Well, progress has been made. I repinned my PCM connector to move the LSF pin from 28 to 45. The HSF is in 46. Changed the tune on the original PTP2 PCM to verify it was happy. I also acquired a MAV2/MPC-19D Marauder PCM and flashed the same tune to a chip to connect to the Marauder PCM. Also re-added the tach pin to the harness. Runs with the Marauder PCM and chip, seems to still have both fan speeds (pins 45 & 46) and I have tach from the PCM now. Is the 'High speed fan' and 'low speed fan' referring to the fan speed or vehicle speed (IE: 'High speed fan' means a lower fan speed that's engaged at higher vehicle speed and 'low speed fan' being a higher fan speed that's engaged at lower vehicle speeds)?

Is there any reason I can't do a recovery flash to the Marauder PCM to flash everything, including the VID block from the Mustang PCM that I've been running?

MPC-19 is the hardware code, the prefix at the end is the revision for the componentry present. (8/c/d) etc.. unfortunately no one in fords inner circle thought it was worthwhile to publish a listing.
All of the ones that I have in the reference I've had to decipha.

That's actual radiator fan motor speed. The new edge mustangs use a 2 speed fan like many fords of that era (90s/00s). The lower speed is used for the a/c and when the coolant temp exceeds the thermostat fully open temp (usually about 15 degrees above the thermostat rated temp). The higher speed is when coolant temp exceeds the radiator saturation temperature (usually about 25 degrees above thermostat rated temp).

The scalars, lsf on, lsf off, hsf on, hsf off are the temps.

The fan turns off at highway speed since it would become a restriction and reduce cooling capacity.

Recovery mode in pcmflash writes the vid block. Go ahead and write your current tune no prob.

So the reason I asked about the fan is high seems to be the lower speed and low seems to be the higher speed. At least that's sure what it sounds like.

thats odd, did you maybe invert the output with the inv switch by mistake?

are you sure the lsf is coming on at all and high speed is working too?

Do a KOEO test to verify

So it seems I mis-remembered. With the Marauder PCM, it only has one speed, but it sounds like the high speed fan. When I turn the low speed fan on, the fan turns on.

Looking at the fan circuit schematics, the low speed fan wire goes to what's labeled 'solid state', which has a ground connected to the PCM Power Relay's ground, and then a line going over to the EDF relay. When the wire is removed from the connector or the pin is changed to another one for the LSF, the fan turns on, indicating the PCM is actively stopping the fan from running so that it's 'fail safe' in the event something went wrong in the PCM or the wire was severed. Looking at the schematic, it looks like the PCM pulls the fan controls to ground. In the case of the EDF relay, it appears the PCM pulls to ground to turn the fan off, and for the HEDF relay, it pulls to ground to turn it on.

yep, thats how they all function

i'm not following how any of that is relevant?

Just making sure I'm understanding the theory of operation and that the fan lines are wired correctly... When I was moving the wires, based on the diagrams and wire colors, it looked like the two were reversed, but when I swapped 45 & 46 (after changing the output in the tune), fan was on immediately at key on, so since the EDF relay is turned off by the PCMs output and the HEDF relay is turned on by the PCMs output, then it's wired up right and operating correctly.

What I'm getting at is that on the homepage pin 46 is not defined, are you sure your high speed fan is working ?

That PCM may be missing an output on that pin. You may need to move the hsf pin to a different pin and reassign it.

Doing a KOEO test will verify.