Frequently Asked Questions (FAQ), Procedures and Resources
This is modelled loosely on the Audi 100/A6 (C4 92-97) FAQ Digest page (see URL)
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Thanks from the staff at STFA (Search the Forum Archives)(or, on a bad day, Search the Freakin' Archives!!!)
Our 43 mm diameter fuel pumps have a finite life. They can fail as early as 80,000 miles or last as long as 250,000 miles. However, since they give little or no warning before they die (a bit longer cranking one or two days before they die), I personally advocate changing them every 100,000 miles (or less). They aren't that expensive ($120) if you do the work yourself. The procedure below works.
Best if you drive the car until the 15 L remaining fuel warning light comes on. That way you don't have to syphon fuel or have your arm in fuel to your elbow. To reduce the fuel pressure in the system, remove the gas cap, start the car and then remove the 20 amp No. 17 fuel pump fuse (panel at the drivers (LHD) end of the dash) and run the engine until it stops. Then remove the rear seat and disconnect the battery (have the radio code handy).
Ventilation!! Take a break if you feel dizzy. Better yet wear a vapour mask with carbon canisters.
The AAN will develop misses when there is spark plug, spark plug boot, coil, power output stagen (POS) or even MAF to Turbo hose problems. It can be nightmare to find the problem. Fortunately, there have been enough BTDTs that there are some logical procedures to help you figure out what the problem is an how to fix it.
One missing and hesitation diagnostic procedure (for POS and Coils)
This one should help you to sort things out. If the miss is just under boost, it is most often a coil but could be plugs or boots or even the MAF to Turbo hose. If the miss is all the time, it is likely one of the POS channels dieing.
Follow the procedure below and you should be able to sort it out.
The fuel pump is powered by the general 12V power system. In stock form, the power goes from the battery (under the rear seat) to the ignition switch and then all the way back to the fuel pump (located in the trunk area, behind the battery). Since the wire gauge Audi used isn't the best, there are line losses of about 1 V. This may not seem like much but under load, e.g. Wide open throttle (WOT) and big boost, this lost 1 V is very important to the pump's ability to provide enough fuel. The solution is to relay the fuel pump to the battery (about 4 ft from the fuel pump). Sean D. and I developed a procedure to install such a relay. The result is the write-up in the URL below.
Life at 200k
By Paul Rivera - Quattro Quarterly, Fall 2001
For the Urq/S4 owners reading this, it will all be familiar. For those of you coveting ownership of this marvelous car, here is a little insight of what it's like to own one for an extended period.
Older Mercedes models, like the W123 chassis have a great reputation for durability and being able to run up to 1 million kilometers. Just ask the taxi drivers in Germany. In my opinion, modern Audis (1986 and newer) have that same capability. Our family Audi fleet is an example of this.
Having two S4s in our family, the '93 at 200K miles, and the '94 approaching 120K miles, has given us quite a knowledge base of just what one can expect "real-world" in owning these incredible cars.
Mike Rooney, of Ingolstadt West Audi Service in Chatsworth, California, is my resident S4 "Meister-wrench". I tapped him to assist in providing additional information for this story. He helps to maintain our fleet of 5 Audis in the family. Manfred Hageldorn, formerly of Rusnak Pasadena, moved back to Augsburg, Germany, and the other great Rusnak wrench was Johnny Reyes, recently hired by Audi Powertrain Development. Mike has taken their crown as the best Audi mechanic in this area. Manfred by the way, is now wrenching BMWs and has recently told me how superior he feels Audi engineering and production quality is to BMW (he is a little biased).
C4/S4s, built from 1992 to 1994, and C4/S6s, from 1995 to 1997, are identical in chassis design to the 100/A6 model sold between 1992 and 1997. C4 is the chassis identifier for a full size Audi chassis built in this era. Audi V8s and A8s are "D", and Audi 80/90 as well as A4 models are "B" chassis. We are now on the C5 chassis series (A6 1998 to?). Changes in tuning for the Urq/S4 (original) included not only power train, but springs, shocks, front sway bars, and rear sway bars fitted in some years. Also, there was a running production change with an additional firewall bracing upgrade installed starting in late 1992 and early 1993 C4 models. Interior details, like white face gauges, premium leather seating, and Bose Stereo systems were all standard in the USA specifications for this top of the line model. For the lucky few, S6 station wagons were imported between 1995 and 1997. Unfortunately, Audi USA never imported the V8 version of this car sold in Europe between 1992 and 1997. The V8 powered S6 Plus, sporting the S8 motor and 326 HP was the best and last of this model. Not to fret, as you read this, the new C5 based S6 Avant, with the S8-V8 and 340 HP, will be on the way to your local Audi dealer. Get one while you can!
The single most important section of this fine car is it's incredible power-train-five cylinders, 20 valves, dual overhead camshafts, fuel injection, and most of all, a sweet turbocharger. This motor, referred to as AAN, began life in the USA as a 3B motor in the 1991 Audi 200 20V turbo quattro. Audi engine boffins changed just about everything on the intake, injection and ignition side, as well as a totally different transmission, making this power-train the greatest and last example of the Audi 5 cylinder engine. As a side note, Acura-Honda, Volvo, and Fiat started making 5 Cyl. DOHC motors soon before Audi stopped. A real testimony to the vision of Dr. Pi?ch, the man behind the Audi 5 Cyl. concept.
You could call me a maintenance freak. I abhor any dirty or old lubricant, old anti-freeze, and especially old brake fluid. Timing belt changes become a religious discipline. Service schedules from the factory in my opinion are tuned to lower costs in the first tier of ownership, without regard to extending the life of the vehicle's power-train and brake system. How many times have you read "lifetime filled". Lifetime of who or what, the component in question? With my mentality of maintenance, I have received the reward for extremely long life of all of my cars. What I have found is that most S4 owners tend to be the same towards their cars.
There have been so many studies from MBA types that find the most optimum time to sell your car is below 50K miles. As the S4s in my family have been very reliable, I see no reason to sell the car at all. In fact we are expecting to keep the cars for some time to come.
Mike Rooney and I had a long lunch recently and reviewed not only the work that was done on our cars, but also things he has seen with all the other S4s he services.
When we listed all the areas of potential maintenance, it seemed like quite a scary list. Not all of these things have happened to either of our cars. However, if you look to buy a used one with high miles, or you too are set on a "keeper", you can expect some or all of these areas to need attention at some point in the car's life.
Mike says "Keeping clean lubricants and fluids is the cheapest form of preventative maintenance. I advise using high quality synthetics, like Castrol Syntech, Mobil 1, and Red Line. Change your synthetic engine oil at 5K intervals to be safe. Always use a German brand such as Mann, Mahle, Knecht, or authentic Audi Oil filter. Do not use Generic Orange, Yellow, White, or Blue filters (no names listed for law suit sake). The correct filters have 2 internal valves, a drain back valve and a by-pass valve. Most generic K-Mart/Pep Boys brands do not. If you use ordinary motor oils, please take care as I have seen even the famous Yellow brand form a gelatinous goop that can coat valve train components and end up clogging the pickup screen of the oil pump and cause oil starvation. I advise use of Castrol GTX, or Kendall Racing, with 3K oil change intervals. If you use a "Quick-Lube" place for oil changes, bring them the filter. Change the transmission and rear differential lubricant at 60K intervals at a minimum, preferably @ 30K using Audi/VW or Red Line synthetic gear lube. Brake fluid should only be Dot 4. Castrol, Mercedes, Audi/VW, or ATE. I do not advise use of domestic brands. Change at least annually and be sure to flush and bleed the clutch master and slave cylinders at the same time. Hydraulic Fluid for the steering/brake pump should be flushed and changed at the 30K service (at least), with the filter screen replaced if necessary. Use Pentosin or Audi/VW Synthetic only. Coolants should be phosphorous free, like the Audi/VW brand, Mercedes, or some other high quality brand. Change this annually as well. Most important major service is the 60K, when the timing belt, water pump, tensioner, and serpentine belt should be replaced in one shot. Saves a lot of labor cost as the water pump often does not last to the 120K service. Make sure you get your car on a hoist once in awhile so you can inspect the areas near the rear differential, drive shaft, and CV boots. Hard to see some problems when you are underneath the car.
It is rare that I have seen any S4 with enough miles to warrant rebuilding the bottom end. Valve trains seem to last well over 250K, with good fuel, clean lubricants and coolant, and a tuned motor extending the heads life. S4 motors well maintained could last up to 350K miles.
Below the approximate miles are listed in which you can expect parts to fail or need changing, and areas that need closer scrutiny.
Timing Belt and Serpentine Belt 60K.
Timing Belt Rollers and Tensioner, 60-120K
Power Steering/Brake Pump. Usually the seals will fail at 60-100K, and if you get an authentic ZF Seal kit, you can save the cost of buying a new pump.
Brake Accumulator. This is an expensive part and will last anywhere up 200K miles, yet may fail as early as 50K. A valve inside of the unit fails and renders the unit useless.
Steering rack. Usually it is seals as well that fail in this part. They can be re-sealed cheaper than replacing the unit. This will occur somewhere between 80-150K miles. Mike has resealed both of our cars once. High pressure accumulator and steering rack hoses are long life and start needing replacement around 120-150K. Several of these have been changed in either car.
Cooling System. Hoses. At 90-120K miles, consider changing all of them at one shot. Saves grief later. Aftermarket sources of German OEM quality are less than $175 for a complete hose kit. The little hose for the turbo coolant is hidden and should be replaced as well. Radiator. Neither of our cars have needed replacement yet. Unlike our V8 and 1991 200 where they failed at about 100K miles (plastic end tanks crack).
Plastic Heater Valve fails @100-200K miles.
Coolant Bottle and Cap will need replacing @ 50-120K miles.
Water Pump 60-120 K Miles. Clean coolant helps extend life.
Cooling Fan Motor. Have not changed yet in either car.
Aux cooling pumps. They seem to develop leaks more than just fail. Usually before 100k. Both have been changed on both cars.
Heater core. Not changed yet, again clean coolant extends life, 120-200K miles is typical for life.
Hoses. The braided portion of these hoses can leak. Audi did have a recall, and I have had both of our S4 hoses changed, at 50-100K Miles.
Injectors. Still have the originals in both cars. Use of Techcron at each oil change service, good fuel, and frequent change of fuel filter @30K intervals) is needed for long injector
Fuel Pump. When it starts making lots of noise, time for a change. Usually 100-150k miles. '93 was changed at 170K, '94 has yet to go.
Turbo Charger. Clean oil, and letting the engine idle and the turbo cool down after a hard run helps as well. Intercooler hoses will fail at 50-200K depending whether the rubber rots or the excessive boost on a chipped car blows it out. MTM makes some reinforced hoses that are worth upgrading to, or change them all to Silicone "Samco" hoses.
Brake system Calipers Front. Stock Girling G60's are bulletproof with clean fluid. We changed both of our cars to the Mov'it Brembo/Porsche 993 TT calipers and matching rotors.
Brake Pads Front 10-25K Miles
Brake rotors front should be changed at 2-3 pad change intervals. Check minimum thickness specs and measure.
Brake pads rear Up to 100K on these.
Brake rotors rear. Maybe change @ 100K-150K if needed. Maybe resurface is ok too for one pad change. Again, check for the thickness specs and measure/replace accordingly.
Brake caliper rear. Here is an area of concern for our east coast and wet weather area owners. The hand brake cable can get rusted quite easily and lock up. Keep the entire handbrake mechanism and cable assembly clean and lubricated, and make sure the cable boots are intact and packed with some light grease. Neither of our S4s have been afflicted with this yet. My 1986 5KCSTQ had it bad as it was an east coast car.
CV joints. These usually last up to 300K Miles if the boots are intact, full of grease, and never exposed to dirt. Ours are original on both cars.
CV boots. These can need replacing somewhere around 80K-120K miles. When you change your shocks or suspension, change the boots at the same time. Inspect them regularly at each oil change.
Suspension. Front lower control arm bushings are the first to go, with sub-frame bushing needing replacement if the car has been driven hard or on really bad roads.
Steering damper goes out about the same time. 100-150K miles. Tie rods and ball joints can last up to 250K miles.
Front Strut Bearings take a beating and need replacing when you change your front shocks if not sooner.
Rear suspension is pretty reliable with the exception of rear camber links at 120-150k miles. Shocks. 80-120K miles on the front. Rears last longer, but change all four at once. Mike Rooney likes Bilstein. Konis are great too. Personal subjective preference. Both S4s have Bilstein, with different valving on each of the cars.
Springs start to show sag at around 200K miles.
Wheel Bearings. Not changed yet. Mikes says they can and change them when they are noisy.
Interior. Only the leather seat side bolster driver's side shows wear on either S4. All other interior pieces are in great shape. If you use floor mats, chances are your carpets are fine. Audi interior quality just cannot be beat and it only gets better in the newer cars.
Ignition. Spark Plug connectors. Here is a 60K item. Best to change them @60K service along with the plugs. Especially if the car is chipped. Seems to be a dealer only item, but Blaufernugen has them as well.
Spark Plugs. Use ONLY Bosch F5DPOR Platinum. Change at 30K intervals. Do not even think about a different plug.
Crankshaft Hall Sensor. If the car has hot start problems, this is usually the culprit, but has not failed yet on either car. Mike sees this rarely.
Oxygen Sensor. Change at 30K intervals if in doubt as by 60K they are usually not working well. Aftermarket Bosch with Audi connectors are a lot cheaper than the dealer. You can use the universal 3 wire, but the $ savings is only about $30-$40 and to me not worth the work in splicing in the wires.
Exhaust System. Audi spent the money on a high quality system, and we have not had to change it yet. Folks in the snow belt and wet areas may have different experiences. If you do change, use a stainless steel replacement like Audi original, or a quality stainless like a Stebro.
Catalytic Converters. They seem to have a long life. Have not needed changing on either car. Keeping the motor in tune has helped, I am sure.
Electrical systems. Audi really worked out the bugs and S4s are not plagued by any systemic flaws. Alternators are high output and rarely fail. Starter motors can last to 250K miles. Neither car has had either changed yet.
Instrument lighting is a small gripe. The exterior temperature gauge backlight fails eventually, and either means replacing the unit ($150) or re-soldering a replacement bulb. When you pull the instrument cluster to change a bulb, change all of the bulbs at one shot.
Seat heaters. Usually the driver's side will fail sometime up to 150K miles.
Sunroof switches @100-200K miles. Window motors and Seat motors rarelyfail.
Clutch. This depends on driving style. '93 changed at 150K, '94 changed by first owner under warranty at 32K miles. He was a gorilla.
Master and slave cylinder life is dependent on clean and fresh brake fluid. When changing the clutch, change all related parts such as pressure plate, pilot bearing, thrust bearing, and if necessary, the dual mass flywheel. Also, change the rear main seal, using only an original Audi factory part. Aftermarket seals seem not to be as good says Mike.
Air Conditioning. Sensors need replacing from time to time, and also the temperature control flap motor gives out at about 100K.
Interior fan motor usually needs replacing by 150-200K. Same on my V8, and my 1991 200. Related hoses may leak more with age then mileage.
Compressors seem to have a long life and rarely need replacing. No real trouble areas.
Vacuum hoses can be a problem. Especially the ones that run along the firewall that are covered by a plastic trim piece. The rubber rots and the clamps do a poor job. Change the hoses and the clamps when needed.
C4/S4s may be the last of the Audis that can be considered for ease of owner maintenance. As the new cars increase with technology, it becomes increasingly complicated to diagnose repair without the proper tools. There is a cool program for a PC laptop that will read all of the fault codes and reset the computers. You still need skill for the repair.
So here we are at 200k. What shape is the car in? Oil consumption is about one quart per 2K. A little smoke blows out the back when the car is cold, and we think it is time for the turbo to be rebuilt. The body is tight and handles well. Driver's seat needs reupholstering. Pearl White paint is in great shape. It really feels like the '93 can be driven for another 100Kmiles with just normal service. I am completely satisfied with this car (and the '94), and my son enjoys driving it every day. Practical hot rod if there ever was one. He can fit a 4-12" speaker cabinet and an amp head in the trunk, two guitars in the back seat and a band mate or two as well. I also have enjoyed watching the resale value stay strong. I hope to write again when this '93 hits 300K.
Best Audi quattro definition ever by 4 wheeler mag
"I hope that I will soon forget the Audi Quattro. Until I do, I shall continue to worship that bitch goddess Success at the expense of friends, family, honesty and decency - anything to be in a position to have one. The Quattro is evil, an insidious witch in the guise of state-of-the-art engineering, a circe who commands your obedience every waking moment and a succubus who haunts every dream. She's the seductress who recreates That First Time all over again, who snips all your tethers to innocence and changes your life forever." - Four Wheeler Magazine, August 1982
The Cam Position Sensor is used by the ECU (Engine Control Unit, i.e. the Motronic Computer) to figure out where the pistons are early in the starting cycle rather than waiting for the crank position sensor to come around. If the ECU does not get a cam position sensor signal, it will not fire the fuel pump relay. Once the engine is running, the ECU will use the crank sensor position sensor to keep track of things. If the cam sensor fails, a "2113" blink code will be thrown (into memory) and check engine light will come on. If it fails while running, you can keep driving but as soon as you turn the engine off, you are done. The engine will NOT re-fire until you fix the cam sensor. Location photo and diagrams in the URL links below.
The ECU controls the fuel pump (FP) relay (J17)(PN 4D0 951 253) (located under the driver's side (LHD) knee bolster, right end of relay panel). The ECU will not engage the J17 until it has a signal from the cam position sensor (G40) during start-up and then the engine speed sensor (G28) during running. However, the FP relay does more than that.
Update: April 4/09: 4D0 951 253 which was the 208 relay is now superceded by 4D0 951 253B, the 372 relay. KATE's verbiage is:
"contact close relay for fuel pump
relay location/code no.: 6/372
to be used for code no.: 208"
Follow the URL for more info as to why the J17 is SO important.
New AAN ECU connector pin-out with wire colours and comments
This should help if you are trying to track down a problem (electrical pun intended). You will still need a wiring diagram from the Bentley:
Pin-Out for the AAN ECU (or Engine Control Module (ECM)) T55 connector
The AAN ECU connector has 55 pin positions. The pins are arranged in three rows. The longest row has 19 pins, Pins 1 through 19. Pin 1 is nearest the metal release lever on the harness connector. The middle row is Pins 20 through 37, with Pin 20 nearest the metal release lever. The last row is Pins 38 through 55 with Pin 38 nearest the metal release lever. Not all pins are used.
The following are the Pins and their assignment. The information is taken from the Robert Bentley manual with comments based on VAG service manual 143 (VAG143) information and some experience.
The Letter/Number, e.g. N71, are for the devices that are either being controlled or are sending a signal to the ECU. The Letter/Letter code is the wire colour code. Not all pins are used - especially on the standard transmission cars.
Wire Colour Codes used in the pin-out list below:
BK = Black
BL = blue
BR = Brown
CL = Clear
G = green
GY = gray
LT G = Light green
OR = orange
V = Violet
W = white
Y = Yellow
W/V = white with a violet stripe
R/BK = red with a black stripe
1/55 - Output to Power Output Stage - N122- G/W- for Coil No. 1 (N122 Pin 4/4)
2/55 - Output to Power Output Stage - N122 - V/BK - for Coil No. 2 (N122 Pin 3/4)
3/55 - Output to Fuel Pump Relay - J17 - BR/Y - ECU triggers the relay after it gets the G40 cam position sensor signal
4/55 - Idle Air Control Valve (aka Idle Stabilization Valve (ISV)) - N71 - W/Y the ISV is used to control the idle, e.g. when the air conditioning compressor comes on.
5/55 - Output (Fuel) Tank Breather valve N80 - W/R- Controls the evaporative emissions frequency valve - N80 - to cycle evaporated fuel vapours back in to the engine (NOTE: Bentley shows this as T55/3 on page X57 - presumably in error) VAG143 has it as N80.
6/55-Connection to A/C Control Head -E87- G/Y - Used to shut off A/C for up to 12 seconds when throttle is opened rapidly at speeds under 7 kph and shut off A/C for up to 3 seconds when in first gear and throttle position is at 65 degrees or more (full load) Ref: VAG143.
7/55-Mass Air Flow (MAF) Sensor - G70 - G/W - the MAF allows the ECU to know how much air (by mass) is heading to the cylinders so it can adjust the fuel, boost and timing to suit the conditions
8/55- Input from Hall Sender - G40 - GY/R - signal wire - Not lack of signal = Blink code 2113 and the engine will not start
9/55 - Barometric sensor - G16 - GY/BK - provides a signal to the ECU to help control boost at higher altitudes - between 1000 and 4000 meters - prevents the turbo from spinning over 155000 rpm.
10/55- Ground for Lambda (Oxygen) Sensor - G39-BR/R
11/55 -Input from Knock Sensor No. 1 - G61- G/G - for cylinders No. 1, 2 and 3
12/55- Power Supply (+5V) out to Hall sender - G40; Throttle Potentiomenter (G69) and Altitude Sensor (F96) - R/R -
13/55- Output to Data Link connector "L" for diagnostics - W/R
14/55-Ground for Fuel Injectors (N30-83)- BR/W - ground on intake manifold
16/55 - Output control signal to Fuel Injector No. 5 - N83 - W/BL
17/55- Output control signal to Fuel Injector No. 2 - N31 - W/BR
18/55- Constant power supply to ECU J220 - R/R- from power terminal 30 (+12V) Fuse S26 (5A) - passenger footwell
19/55- Ground from the ECU for various ECU controlled devices - BR/R - to intake manifold
20/55 - Output to Power Output Stage - N127 - BK/Y - for Coil No. 4 (Note - some early versions of the Bentley have this as Coil No. 5 - but this is wrong, it is 4 - check it yourself) - VAG143 has it correct.(N127 connector Pin 4/4)
21/55 - Output to Power Output Stage - N127 - BK/W - for Coil No. 5 (Note - some early versions of the Bentley have this as Coil No. 4 - but this is wrong, it is 5 - check it yourself)- VAG143 has it correct. (N127 connector Pin 3/4)
22/55 - Data Link Connector - W/BL - linked to Check engine light (Malfunction indicator lamp) - also used in the blink code check.
23/55 - Output to Power Output Stage - N122- BK/GY signal for Cyl #3 Ignition coil (N122 connector Pin 1/4)
24/55- Power Ground for "actuators" other than injectors - Not found in Bentley, presume BR/R, ground to intake manifold
25/55- Mass Air Flow (MAF) Sensor (aka - hot-wire air volume meter) - G70 - G/V- Burn off signal from ECU - every time the engine is switched off, the hot wire is heated to 1000 deg C for one second to keep it clean
29/55-Input from Knock Sensor No. 2 - G66 - W/W- for cylinders No. 4 and 5
30/55- Ground for ECU and ECU sensors - G/BK
31/55- Fuel consumption signal for trip computer - BL/BK - Note: only used in N.America on 92 spec cars
32/55-Output toTrip Computer Boost Pressure Gauge - Y/BL - Note: only used in N.America on 92 spec cars
33/55 - Waste Gate Frequency Valve - N75 - Y/R - also know as the charge pressure control actuating valve - lets the ECU control the boost - by dumping excess boost through the waste gate
34/55 - Output control signal to Fuel Injector No. 3 - N32 - Y/BL
35/55 - Output control signal to Fuel Injector No. 4 - N33 - Y/G
36/55 - Output control signal to Fuel Injector No. 1 - N30 - W/V
37/55-Switched +12V for all 5 Fuel injectors (N30-N83) and MAF (G70)- BK/R - 15A - Circuit Breaker S72
38/55-T6ag Coding plug -Pin 1-GY/W
39/55-T6ag Coding plug- Pin 2- GY/Y
40/55-Input from Engine Speed Sensor - G28 - V/BK - Also connected to Ch.28 in the A/C head (you can read out RPM in the A/C head)
41/55-Signal from A/C control module -W/W - signal used by ECU to increase idle speed through ISV control when A/C compressor is activated (actually just maintains the idle speed when the extra load from A/C compressor is added to the system during idle)
42/55 -Gear selection input - Automatic only
43/55 - Not used
44/55 - Intake Air Temperature (IAT) Sensor - G42 - BR/BL - the ECU uses this signal to dial back timing (and power) to prevent pinging if the intake air temp is too high
45/55 - Engine Coolant Temperature Sensor - G62 - GY/BR - the one at the back of the head that the AAN ECU uses to figure out if the A/F should be enriched because the engine is cold.
46/55- Not used
47/55- Input from Crankshaft Position Sensor - G4 - V/V - used by the ECU to control ignition and fuel injector timing
48/55- Combined ground through ECU for G4 crankshaft position sensor and the G28 engine speed sensor - R wire from G4 and BL wire from G28
49/55-Input from Engine Speed sensor - G28 - GY/GY
50/55- Road Speed signal output (input?) to Instrument Cluster-G21-W/BL-signal also goes to Automatic Climate Control Head Channel 17 - which you can read out speed as well.
51/55- Not used for standard transmission cars - relates to shift point for automatic trans cars
52/55 - Idle Switch - F60 V/V- a microswitch inside the G69 throttle potentiometer that tells the ECU that the throttle is closed
53/55 - Throttle valve potentiometer - G69 - GY/GY the potentiometer on the throttle body that tells the ECU the degree to which the throttle body is open
54/55- Not used for standard transmission cars - relates to automatic trans cars
55/55- Output to Data Link connector "K" for diagnostics - G/R
To clear engine fault codes in the AAN ECU, you can either disconnect the battery for 30 seconds (you will need the Radio code) or you can pull the ECU circuit breaker.
If you have accessed the ECU before, i.e. carpet is cut, etc. then you can clear the ECU codes by pulling the ECU circuit breaker (S64) for 30 seconds, in the red holder in the photo. (Photo courtesy of SJM Autotechnik (http://www.sjmautotechnik.com/troubl...ng/20vpin.html)