MAC-14 Diagnostics

Ben Swann benswann at
Wed Sep 26 16:45:37 PDT 2007

I'm still trying to get some resolution here.  Since I wired this up a few months back,
I re-checked my wiring.  The wiring is basically as in the diagram shown on SJM site:  page down where
three diag. connectors, LED and jumper are shown.  That is how I have it.  It should
also work with the "dirty" cable for VAG_COM - but didn't.

And it also jibes with the Bentley and there nebulous description based on prioprietary
test equipment.  Also there are some confusing uses for the ECU pins in question: namely
Pin 33 is supposed to be positive + , but I only get maybe +4V and seems spurious -
sometimes under 1V w/respt to ground.  I'm wondering if I should just make this wire a
switched 12V like to pin 35 instead?  The Bentley diagram and some other sources have
this shown as diag. trigger at fuel pump relay - I am bypassing the relay altogether as
not needing the fuel injection portions and have made a separate switched wire.  I have
a relay provisioned, but really should not need it.

Also, when I jumper from ECU pin 5 "L" to ground as shown, it kills the engine.  At no
time am I able to get the LED lit.

Has anyone else run diagnostics for the MAC-14 lately? Would be real nice if someone
elst has "hacked" the harness or done an MC-2 install in other vehicle and knows what
I'm talking about.

I have run diags on an MC-2/MAC-14 eauipped 200Q before, so I know that it can work.
Just when you are starting with a harness that had the diag. connectors cut and have to
rewire it to work "standalone" in an older car, now I'm wondering if Bentley and other
sources are completely correct.


Ben Swann wrote:
> I'm trying to run codes on my MAC-14 ECU which is currently setup to
> do only ignition
> for my Megasquirt setup.  The wiring harness has been completely
> transplanted, and I
> installed connectors for the "dirty" OBD to connect to VAG-COM.
> VAG-COM is not picking
> up on it.
> Has anyone retrieved codes via VAG-COM for the MAC-14?
> I will try connecting to flash the codes, but would be nice to use
> the OBD features.
> Anyone had much success flashing the codes using fuse and CEL?  I
> don't have identical
> wiring with Fuel Pump Relay, but have wired according to Bentley.
> Wondering if I am
> missing anything for this.
> Ben
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