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Error 2142 from ECU...

In message <34FC01C0.FA331CCC@poboxes.com> Gerard writes:

> I checked the knock sensor by hand, ie. grab it a feel for play and
> it feels solid in place. I will check the wiring continuity to the
> plug on the firewall and will follow the other tip to check continuity
> to the ECU. Question I have is this: what pin on the ECU plug is for
> the knock sensor? I am running a MAC13A (bet none of you have that one,
> except for other South Africans), it seems to be a MAC12D derivative,
> ie. 2 boards, top board has small cutout in top corner. What is the
> pin for the KS?

Should be good for MAC11/NAC12/MAC13:

Audi quattro - MB engine (MAC-12) ECU wiring

The ECU is connected to the wiring harness via a
latch- and-swing connector.  With the  ECU
removed from the vehicle, the wiring harness
connector should be viewed with the plastic
prongs on the right and  the locating lugs along
the side of the connector at the top. The upper
left pin is Pin 1, with numbering proceeding
along the connector to Pin 18 at the top right.
The bottom row is also numbered from left to
right, from Pin 19 to  Pin 35.

1.   Blue/Wh   Cold Start Valve (N17)
2.   Br/Ye     Chassis
3.             (USA - carbon canister)
4.             (USA - decelleration valve)
5.   Br/Ye     Chassis
6.             (USA - auto transmission)
7.   Mauve     Idle  Stabiliser (J142), Oil
               Pressure Warning Controller
8.   Blue/Bl   Frequency  valve  (N7), T35/3
9.   Br/Red    Chassis
10.  Blue      Coolant Temperature (G62 - side
               of block)
11.  Blue      Engine RPM Sensor (G28)
12.  Mauve     Ignition Timing Sensor (G4)
13.  Red       Ignition Timing Sensor (G4)
14.  Blue/Wh   Electronic Thermoswitch (F76)
15.  Br        Knock Sensor (G61)
16.  Wh        Knock Sensor (G61)
     Br        (shield for above)
17.            (USA - electronic boost gauge)
18.  Br/Ye     Chassis
19.  Gr/Ye     Wastegate Control Valve (N75)
20.  Grey      Idle Switch (F60), Idle
               Stabiliser (J142)
21.  Br/Red    Fuel Pump Relay (J17)
22.  Gr/Wh     Electronic   Ignition
               Power Stage (N70)
23.  Br        Inlet Air Temperature Sensor (G42)
     Br/Red    Hall Sensor (G40)
24.  Blue      Hall Sensor (G40)
25.  Red/Bl    Hall Sensor (G40)
26.  Wh        Full Load Switch (F81)
27.  Gr        Hall Sensor (G40)
28.  Br        Shielding for 11, 12, 13, 29
29.  Grey      Engine RPM Sensor (G28)
30.            (USA - O2 sensor ground)
31.  Bl/Wh     Fuel pump relay fuseholder
33.            (USA - O2 sensor signal)
34.  Br/Ye     Chassis (USA - California)
35.  Bl/Red    Power via Fuse (S34, 10A)

> One final question: why would this fault show almost all the time at
> about 115km/h doing about 3000RPM? Why occassionally at hard launch,
> but with tacho below 3000RPM? Why, when it happens, does it go away
> if I back of very slightly from the gas, and return when I re-apply
> gas for some 100RPM more spin and then the light stays on until I
> back off the gas again?

Dunno.  Have to check the code.  Orin can tell you _exactly_ why the code
gets set.

 Phil Payne
 UK Audi [ur-]quattro Owners Club