[s-cars] 1.8t Coil Pack Conversion Pin out info (with OE POS info)

[Dave Forgie]

I  haven't finished the conversion write-up yet but some of you are
interested in the pin-outs and other POS related info, so here it is:

1.8t Coil Pack Conversion Pin-outs

The 4 pin 1.8t 06B 905 115 L Coil Packs have their pins numbered.  The
function  of these four pins is as follows:

Pin 1 = switched power to the primary side of the coil - connect to the
yellow power input wires on the firewall metal connector rack via the
scrounged VW three pin O2 sensor connectors from item No. 8 in the parts
shopping list.

Pin 2 = Ground for built-in Power Output Stage - connect to pin number 2
(brown white wire) of the 4 pin connector feeding power output stage
(POS) N122 (the one for cylinders 1,2 and 3). Use one of the regenerized
Jetta III taillight connectors (shopping list item No. 7) to make these
connections to the OE ECU to OE POS four pin connectors, as per the
pin-out below.

Pin 3 = The 5 V DC signal from the ECU to control the POS switch.  Use
the regenerized Jetta III taillight connectors (shopping list item No.
7) to make these connections to the OE ECU to OE POS four pin
connectors, as per the pin-out below.

Pin 4 = Secondary Coil Ground - connect to corner bolt of cam cover
where the OE coil pack ground was located.  Use a ring-type terminal
under the bolt.

Refernce for the above (to check): Page 97-371, Wiring diagram No. 41/4
of the Jetta/Golf IV repair manual Edition 11/99)

The POS control wires come from the 55 pin ECU connector.  Three for
cylinders 1, 2 and 3 are in one four pin connector that goes to POS
N122.  The other two, for cylinders 4 and 5  are in the four pin
connector that goes to POS N127.

You need to connect Pin 3 of the 1.8t coil packs to the respective
cylinder's ECU wire via the regendered Jetta III taillight connectors.
The ECU to POS pin- outs are as follows:

ECU pin 1/55 = Green wire with a white stripe for cylinder No.1 (N122
connector Pin 4/4)
ECU pin 2/55 = violet with a black stripe for cylinder No. 2 (N122
connector Pin 3/4)
ECU pin 23/55 = Black with grey stripe for cylinder No. 3 (N122
connector Pin 1/4)
ECU pin 20/55 = Black with yellow stripe for cylinder No. 4 (N127
connector Pin 4/4)
ECU pin 21/55 = Black with white stripe for cylinder No. 5 (N127
connector Pin 3/4)

NOTE: The Bently on page X52/Electrical pg. 24 is wrong about cylinders
4 and 5.  The above is correct.  Pin 2/4 of the OE POS connectors is the
Primary coil ground that the POS controls.

Original Equipment POS Functions (Only if you don't believe the above)

The AAN is a five cylinder car (Duh), therefore there are five spark
plugs. The 3B before the AAN only had one  coil and a more or less
conventional Hall-effect distributor (c/w rotor and five wires). The
engine engineers at  Audi figured out that IF they provided each
cylinder with its own coil, then the engine could make more horsepower
(about 10 DIN hp more), bringing the nominal flywheel hp up from 217 to
227 hp (220 to 230
 DIN hp). The trouble was they needed some kind of computer controlled
switch to fire these coils in the correct order and at the correct time.
Enter the POWER output stage or POS, not usually confused with piece of
sh*t but eventually, yes, they all are. But I digress.

 The AAN has two three channel POS units mounted on the firewall (they
were made for six cylinder cars). These devices are named N 122 for
cylinders 1, 2 and 3 and N127 for cylinders 4 and 5 (with one spare
channel). Each POS has four pins on one side and three on the other. The
four pin side is the side where the ECU signal comes in. The three pin
side is connected to the primary side of the coils. The primary coils
wires are black and are labled with their cylinder number. They are NOT
the input TO the coils as often
 thought. They are actually the outlet for the current flow FROM the
primary side of the coils. The power feed TO the primary side of the
coils are yellow wires that come from the two white three pin connectors
on the metal connector rack on the firewall. The ignition-switched 12 V
power is fed from the these connectors to the primary side of the coils.
However, the primary side of the coil has no ground so normally there is
no
 current flow or, as a result, spark. The ground is actually through the
POS unit and pin 2/4 and its white-striped brown (BR/W) wire.

 The ECU (engine management computer, with the aid of a signal from the
crank position sensor (and cam position sensor during starting)), sends
a 5 VDC (or so) signal to the respective channel on one of the POS's,
Inside the POSs, there three transitorized swithes that, when triggered
by the ECU's 5 V signal, send the 12 V current FROM the Primary coil to
ground (through pin 2/4). With the "gate" open for current flow through
the primary coil, this rush of current in the primary coil, "excites"
the secondary coil which in turn produces a high voltage current that
rushes to the nearest way out, which in this case is the spark plug.

 The POSs fail because inside there are some very fine wires that seem
to get brittle with age and/or heat. These wires break or crack,
resulting in poor or intermittent current flow. We call that missing or
hesitation.

 Internally, in the POSs, Pin 1/4 connects to Pin 3/3, Pin 2/4 is a
ground (brown with white stripe that eventually goes to the intake
manifold), Pin 3/4 connects to Pin 2/3 and Pin 4/4 connects to Pin 1/3.
Rember that. Draw a diagram if needed.

 For POS N122, a green wire with a white stripe comes from Pin 1 of 55
in the ECU connector, representing Cylinder No. 1, and connects to Pin
4/4. The corresponding wire from the primary coils is connected to Pin
1/3 on the three pin side. A violet (purple) wire with a white stripe
comes from Pin 2 of 55 in the ECU connector and connects to Pin 3/4 of
N122, representing Cylinder No. 2. The corresponding wire from the
primary coils is connected to Pin 2/3 on the three pin side. Pin 2/4 is
the Brown with white stripe primary coil ground wire. A black with grey
stripe wire comes from pin 23 of 55 in the ECU connector and goes to Pin
1/4 of the N122 POS for cylinder No. 3. The corresponding primary coil
wire goes to Pin 3/3.

 Got that? Good because that comes from the Bentley wiring diagram (pg.
24/X52), Scott Mockry's website (for the ECU pinout) and a convenient
X-ray of a POS that I happed to have.

 Now it gets tricky. For the second POS, N 127, the Bentley is wrong. I
will tell you the truth but you can easily comfirm what I say below by
checking the wires yourself.

 First, the ECU feed for cylinder No. 4 is a Black with yellow stripe
from pin 20 in the 55 pin ECU connector. For No. 5, it is a black with
white stripe from Pin 21/55 in the ECU connector. The tricky bit is the
Bentley mislabled what happens to these two wires when they connect to
the four pin side of the POS. The BK/Y (Cylinder no. 4) wire connects to
Pin 4/4 (which is correct in the Bentley) BUT the Bentley shows the
primary
 coil wire from Cylinder 5 going to Pin 1/3 on the three pin side. That
is WRONG. Its primay coil no. 4 that goes to Pin 1/3 and primary coil
no. 5 goes to 2/3, which corresponds to the black with white stripe wire
from ECU 21/55 going to Pin 3/4 on the four pin side of the N 127 POS.
As always Pin 2/4 on N 127 is the POS-switched ground for the primary
coils.

 If you were paying attention, Pin 1/4 and Pin 1/3 on N 127 are normally
not used. This is the spare channel (the POSs were made for six-cylinder
cars). This allows the potential to swap connectors and/or pins when one
POS channel fails. However, this is a one time fix. When the second
channel fails, you're done.

 This will be on the exam.

Dave F.