Turbo Conversion Gone Bad - MAC 11C Troubleshooting

[Nate Stuart]

Are you pulling the codes with the car running? Otherwise you will
probably never get a fault code. The Mac11 has no fault storage, so once
you turn the ignition off the fault codes go away.

The MFTS sensor doesn't need to be hooked up, nor does the brake light
signal.

blarson at Zeiss.com said:
> All,
>
> My friend and I need help troubleshooting an error on the MAC 11 in his
> 80tq.  Background: The car is a 1990 Audi 80Q converted with a 1987 MC
> motor and MAC 11C ECU.  The code light is hooked up to the brown connector
> under the dash of the 80.  When I pull codes it comes back with 4444 (no
> faults).
>
> Problem:  The fault light comes on as soon as you start cranking the motor
> and stays on when running.  As a result the computer is running in limp
> mode (low boost).
>
> Troubleshooting to date:
> 1) Swapped knock sensors, check continuity to ECU and started car with
> knock sensor out of block.  No effect.
> 2) Verified function and readings of air temp sensor, coolant temp sensors
> to ECU.  Correct resistance and readings at ECU.
> 3) Swapped MAC 11 with another known good ECU.  No effect.
> 4) Checked WOT switch resistance readings.  PASS.  Note this unit what
> taken apart and resoldered as well.
> 5) Shorted terminals 2 & 3 at WOT to make wastegate frequency valve run.
> PASS.

-Nate
'89 90tq
http://www.newtsplace.com/90tq