MAC-14 Diagnostics

Ben Swann benswann at
Thu Sep 27 05:46:42 PDT 2007


I understand that with the wiring in the car from the factory, the 2X2 "dirty" cable
won't work.  I added the wire that should allow it to work - I need to revisit this, but
basically you need to change the wiring to be like the 3B - factory setup is for VAG
1551 test equipment and even with that you need to "cludge" the conections to get a
readout.  For those who want to verify what I'm saying, there it is on/around  D2-190-1
in the Official Factory Repair manual.  Anyway, once I am able to simply blink the
codes, the VAG-COM should be usable.  Right now I have not been able to do either.

I did a continuity test from connector ends to the ECU and things are wired properly
according to the diagrams I've seen.  There are a few connectors that wiring goes
through and even changes colors and I have all this mapped out.  I had to add the
diagnostics connectors that were taken from other scrap harnesses.

Hopefully I'll figure it out today.  I just thought someone else had a clue than just
outright saying "It won't work".  It is supposed to work both ways, just the details are
not clear and Bentley spells out procedure using specialized test equipment without
actually saying what the equipment is/does specifically - it would be helpful to know
what the Adaptors 1594 and US-1115 and VAG-1551 actually are/do

-----Original Message-----
From: Cody Forbes [mailto:cody at] 
Sent: Wednesday, September 26, 2007 11:57 PM
To: Ben Swann; suffolkd at
Cc: quattro at; 'Ben Swann'
Subject: Re: MAC-14 Diagnostics

That page says that Vag-COM will not communicate with the engine diagnostics 
on any 200 other then the 3B :-/. Another portion of thier site says that 
even if it has the 2x2 connectors it must have 4 wires, where some older 2x2 
connectors only had 3 wires.

Any way about it you should be able to blink codes, and the info on Scott's 
site should apply. Going back to basics a bit... is your MAC-14 known good? 
Beyond that, have you used a DMM to check continuity between the cproper 
diag wires and the ECU just to make sure theres nothing funky like a missing 
relay that the current pases through for some only-Hans-knows-why reason?

-Cody Forbes

Ben Swann wrote:
> I think we are confusing things here.  I am simply trying to blink out codes for now -
should at least be able to do this.  In fact I know it can be done and have done it
before, just not on a transplanted MC-2/MAC-14 setup.  And of course this is the MC-2
10V CIS hybrid not the 3B 20V efi , but there are many who subscribe to this list
because the '89 and '90 200Q are more similar to the '91 20V despite that the engine is
Motronic EFI instead of the hybrid variant that was MAC-14.  Furthermore the diagnostics
techniques spelled out in the Bently for the MC-2 are actually quite similar to the 3B
probably closer "procedure-wise" than the MC-1.  But still the option to blink out codes
is there - just sometimes need to install a check engine light, according to procedure.
I have the feeling some other things have been left out and because the procedure calls
for using specialized VAG equipment, one needs to guess at what these things actually
are.  I also think there may be errors or omissions in the diagram.
> With that, it would also be nice to use VAG-COM as the com interface is supposedly
there.  So you are saying that you have not been able to use VAG-COM on an MC-2/MAC-14?
I haven't either, but Bentley and SJM suggest it can be done.
> At the very least, I should be able to blink codes like on the MC-1.
> Ben

> From: suffolkd at [mailto:suffolkd at]
> Sent: Wednesday, September 26, 2007 8:17 PM
> To: 200q20v at; benswann at
> Subject: Re: MAC-14 Diagnostics

> The earliest EU I could read was a 200 20V 3B.  AFAIK the MAc -14 is
> for a MC-2 BAck when Vag Com came out i asked if it could read a 1990 200 10V
> (Mac - 14) we never tested it.  VAg-Com site listed the 3B as the earliest to "work" a
few years ago. I don't know if that has changed.....
> try
> other searchs just brings up some of your posts :-)
> *********************************************************************
>> **Ben*** Right - it  seems like I'm the one who ventures into these territories
first. I have a complete pinout spreadsheet for wiring this beast and how to hook it up
with Megasquirt.  I don't like putting things out there until everything is working
right.  I figured someone has likely done an MC-2/MAC-14 transplant into a 4kq
> or CGT along with associated wiring. - then they would likely have had to go through
this.  ***Ben***
> -Scott by BOSTON

> From: "Ben Swann"
> 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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