Enabling the MIL and reading codes on V6 models

Posted: Fri Dec 03, 2004 2:08 pm

I've done some research and think it is possible to read blink fault codes on the V6 80/coupe, 100/A6? I'll try and keep it simple and will leave out the dissassembly instructions such as removing trim etc, these can be found on various web sites and manuals. Smile

You will need to enable a MIL (Malfunction Indicator Light) like the North American market V6 models (Californian regs). As there is no third socket (blue ~ code output) in the fuse box besides the white and black sockets you will have to rely on the MIL flashing on your instrument cluster which is less hassle as you don't need to make a LED circuit tester and fiddle with plugging it into the sockets. Cool

First remove your intrument cluster Cool

and look at the back where the bulbs are...

okay the unused "CAT" position will be our MIL light. If there is no bulb here use this...

Locate the yellow coloured 26-pin connector (T26) behind the instrument cluster and snip off the tie-wrap which secures the wiring to the connector shell.
Using a miniature screwdriver tease apart the hood from this yellow connector and slide it off to expose the electrical wiring and connection pins as shown in this photo .

Locate pin 24 (twenty four) on the yellow connector. The connector moulding is numbered to assist with this task - it is two from the end as shown in this photo . Pin 24 is an unused connection point, so there should be no wire attached to this pin - until these tasks are complete. Again using the miniature screwdriver (or probe), GENTLY disengage the locking tab for pin 24 and remove it from the yellow connector.
A special crimping tool is specified for these pins, which none of us will likely have access to, so I recommend that a soldering iron is used to connect a 2m length of multicore (0.5mm 2 diameter) cable onto this pin. If you choose cable which is too thick then this will be difficult and the pin may not fit back into the connector.
Carefully return the locking tab of the connector pin (with new wire attached) to its original position and slide it back into position 24 (twenty four) of the yellow cluster connector. It will lock itself into place.
Reassemble the yellow connector hood, taking care not to snag any cables and attach a new tie wrap onto the connector hood when finished. You will now have a 2m length of cable dangling from this connector.

Now comes the knuckle bleeding part Confused

. You need to locate your ECU, first it is a good idea to disconnect the negative terminal on your battery. On my coupe and probably on the 80 the ECU can be found up under the dash accessed by removing the glove-box and trim. The ECU is held in steel frame and should slide out . Once in your hands look remove the multi-connector plug(s) and look for the terminal pin position marked "C14"

this is the blink code ouput from the ECU. Find the corresponding wire on the connector plug and splice into it. Cool

using the other end of the wire you have already crimped to the yellow connector.

Right in theory...

Turn the ignition on and watch as the "CAT" MIL light illuminates...

As the engine starts the MIL light will go out unless there is a fault code! Confused

If the engine runs, you should try to extract and view the trouble codes with the engine running. If the engine will not run, crank the engine for 5 or 6 seconds (never crank the engine for more than 10 seconds!) and leave the key in the 'on' position. Now you need to make a connection between one pin in each connector. On 80/90/Coupe/Cabriolet models, you want to use the two pins closest to you as you stand at the side of the car.

On 100/A6 models, you want to use the two pins closest to the windshield ... if you have any doubts about which pins to use, look at the picture closely and note the orientation of the two connectors. You should connect the two pins for 3 seconds using a short length of wire (try a bent paper clip) Cool

see 12v.org for reading and clearing codes:

Thanks to http://s2central.net/ and www.12v.org for pictures and text for this post!

I will post results when I can be bothered to venture out into a cold garage Laughing

Posted: Fri Dec 03, 2004 2:22 pm

Excellent post my friend.

Jas
Cool

Posted: Fri Dec 03, 2004 3:29 pm

nice one , F28 , as you can see from the other thread I found it hard to accept that this was not possible ; where did you find the schema for the ECU ?

if you read back a bit you will find a thread about this ; struikie and I both set this up , he with his B4/ng and I with my S3 20V ; the difference being that we both had 3 sockets [ the old non white 2 socket will also be OK ] , so no problem digging for the ECU and finding the correct terminal !! as a matter of fact logic dictates that this line comes out somewhere that it can be accessed by the diagnostic equipment ; why don't you trace it and save everyone else the trouble ? maybe it is obvious from another schema ? It must be a switchable earth , as the dash light is fed ex the ignition [try earthing it ]

a few points arising from your post;

struikie found that it was neccessary to use the lowest wattage bulb , can't remember what the colour was , but ~I followed him [1 or 2 W I think ]

I believe you will not get a MIL light , it just acts as a code flasher ; I think the california cars have an extra module to provide the continuous warning light /auto fault read .

as it says in S2 article , joining the wire to the socket on the instrument panel is tricky ; I used wiring out of an old computer , FOC and the correct diameter ; I also installed an old turbo switch [386!] acroos the diag sockets as a jumper wire , ran it to the steering wheel shroud where there is a hole in the bottom half , so I can use at any time [ it has a click clack action ] I was tempted to wire up the light in it , but decided that really was going too far !struikie didn't have autocheck , so he fitted a microswitch on the back of that stalk to start the dump .

if I remember correctly , struikies B4 had a fuseway in the fusebox on the pump solenoid ; a fuse in this for 4 secs also dumps the codes.

but I think you will also find all this only works with the engine running ; as far as I know only the hitachi MPI [20v ] and the bosch MPI [S2] have permanent memory ,the rest having flash only ; maybe the 100's are different .

LB

Posted: Fri Dec 03, 2004 3:52 pm

Great! now the wife will be mad at me when I change our plans for Sunday Laughing

Can't wait to give it a try... I'm tempted to trace the other end of that ecu wire and also to use a switch in the car to act as the jumper... just one question though...

Your comment says "On 80/90/Coupe/Cabriolet models, you want to use the two pins closest to you as you stand at the side of the car" yet the picture shows the pins nearest the centre of the fuse box... not wanting to get this bit wrong, if I stand in front of the car looking at the fuse box, we're talking about the two pins on the right hand side of the connectors... right? If I use the two pins nearest to me when I stand at the side of the car, they would be the two left hand pins Sad

Let me know which is correct, as I've probably just lost the plot a bit Shocked

Cheers all Very Happy

Posted: Fri Dec 03, 2004 4:52 pm

I think that you need to observe the picture and shape of the connectors, that particular set of instructions were from 12.org and therefore left hand drive cars so "standing at the side of the car" may mean the author was standing by the left of the car -drivers side?

LB, ECU diagram was from 12v.org. It maybe the case that the MIL function is embedded into the ECU and there is no separate module? I can only comment for the v6 engine management running OBD1. I couldn't see the wire coming from the ECU to the black plug under the dash as on S2-Central, that's what led me to think that European models don't have this blinkcode/MIL connection wired from the ECU module.

I've managed to crimp a wire in the yellow connector block and insert a bulb, it works when I earth the other end of the wire, just need to take out the ECU and find C14, I've removed the ECU before without too much difficulty, it's well hidden away, on the first attempt I accidently removed my imobilser ecu, well it looks the same! Laughing

I'll try and post some sort of result back by Monday. Very Happy

Posted: Mon Dec 06, 2004 2:21 pm

Really useful info, I'll get on and fit mine as soon as xmas is out the way, I really appreciate the advice and it will save me ££££'s, Thankyou. Very Happy

Posted: Mon Dec 06, 2004 7:16 pm

has anyone got any info on reading a 89 20v 7a i cant find the sockets in the drivers footwell shes running fine but ive a problem with my abs

Posted: Mon Dec 06, 2004 7:48 pm

have you removed the trim to see if the connectors are up under dash (near relays etc)??
basically the same as any other audi of this age with 3 connectors
try here....
http://www.sjmautotechnik.com/trouble_shooting/ecuf20v.html
have a look around this site, lots of info, very useful tho mostly for 5 pot turbo a large chunk of it is related to our steeds Smile

when i fitted the MIL in this coupe i used a 12v red LED and mounted it in a spare legend
this saved having to wire through that yellow plug
just basically 'back-wired' from the connectors to the LED with a tiny switch to activate the circuit hidden away

trouble is you end up getting paranoid and try to pull codes after every trip Confused

Posted: Mon Dec 06, 2004 7:52 pm

cheers ive got the trim off at the minute just fitting a new alarm ill check out the link

Newbie Joined: Dec 11, 2004 Posts: 1

Just to update things...

I've removed the ECU in my coupe, simply remove the passenger side trim under the glovebox and the glovebox itself, pull the four plugs on the ECU and slide it out of the steel bracket.

To locate pin C14 I had to remove the lid on the ECU and look inside, while looking inside the pin outs are marked on the PCB next to the where the pins are soldered to the board. C14 corresponds to the 4th connector (smaller 16 pin yellow one) which is the "C" connector. Pin C14 is 3rd from the right on the bottom row - the pins are numbered on the ECU connector side.

Opening the connector up, and as I thought there is no wire in the crimp terminal! Cool

. Now it just remains for me to crimp a wire here and take it to the wire I've connected to the instrument cluster.

Hope to power up the digi camera to make a few things clearer tomorrow.

Just as a note, my ECU is a Hitachi MMS300 which is the updated version of the MMS200 (similar to the 20v ECU) used on the early '91 to '93 2.8, the plugs are the same for MMS200 and MMS300 ECUs as for the 2.6, I cannot be sure as I've never seen the ECU.

I'll update tomorrow. Smile

Posted: Wed Dec 15, 2004 8:17 pm

Well it's all up and working! Very Happy

I turn on the ignition and the MIL light comes on and soon as the engine starts it extinguishes like what www.S2-central.net says.

Tonight I read the codes by jumping the white and black terminals as per the start of this thread. The codes flashed a sequence of 4 x 4 flashes indicating code 4444 (no faults reported) Smile

. Jumped the terminals again to clear all codes and next I'll unplug the cam position sensor to see how the MIL responds to a non-running engine and give the expected code for a non-functional CPS. Cool

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Posted: Thu Dec 16, 2004 7:00 am

jumping the terminals again just cycles ; I think if you ' fault' the engine with whatever sensor is easiest , after you have fixed it , it just disappears as switching off the ignition clears the codes ...only 20v and S2 have the more complex MPI systems , perhaps all the 4 valve/cylinder models
WOT ? no dashboard jumper switch ?
and let us know if it is a MIL , ie the light stays on when you have a fault , ~I think you will find it is just a code light using a vacant position as on my 7A

LB

Posted: Thu Dec 16, 2004 8:46 am

Malfuntion Indicator Light and code light are one and the same thing are'nt they? It's just Audis terminology?...

An excellent piece of investigative mechanics! Truely first class Oha!

. I love seeing people 'do the impossible' Xmas

...

Posted: Thu Dec 16, 2004 9:18 am

no a MIL is completely different thing ; I believe it takes an extra module which autotests the codes and switches on this light if it finds a fault , because this light stays on until the fault is corrected .
we are just using the unused place on the dash to fit a bulb to read the codes ; on my car it has an oil warning light glass , rendered unwanted by the autocheck ;and mine has MPI !

LB

Posted: Thu Dec 16, 2004 12:49 pm

Yep, Leb is correct, the MIL is a different system to the code lights,,,,,,AFAIK the MIL light was only on the USA spec cars,,,,,as Leb says,,,,,a fault is detected and the MIL light comes on and stays on until the fault is rectified. Simon has just used this spare slot in the dash lights to flash the codes instead of a bulb/led connected to the diagnostic ports.

Jas
Cool

Posted: Thu Dec 16, 2004 1:20 pm

struikie and I worked out the fine detail and did his 4/ NG and my 20v some time ago ; not having autocheck he managed to fit a micro switch on the end of that stalk , while I robbed an old computer and fitted one in the steering wheel shroud [ if you look underneath there is a suitable hole ]
but you are wrong about US cars jas , most don't have this , it is one of californias little specialities ; for some reason they alone of all the states are allowed to add to the american C&U regs

LB

Posted: Thu Dec 16, 2004 1:23 pm

I was nearly right Razz

Jas

Posted: Thu Dec 16, 2004 2:34 pm

I think the best way to resolve whether this is a just a code flasher or a fully operational MIL will be for me to unplug something like one of the knock sensors. The fact that the light comes on when the ignition is turned on and turns off when the starter fires the engine is what happens with MIL equiped cars when there are no fault codes stored which is what I currently have.

In theory all it takes to illuminate the MIL if a fault is detected is for the ECU to send a continuous signal voltage to the bulb via the code output.

I think that from '96 all cars came equipped with a MIL light as part of the OBDII spec. Californian OBDI cars required the MIL back in the early 90's and the other 49 states had the function wired up but with no bulb, obviously Audi America installed the bulb for those cars going to CA.

Posted: Thu Dec 16, 2004 3:07 pm

close ; but not close enough I fear ; someone I know in brooklyn had one and reckoned there was no wire to that position [ guess who had the panel out to change some bulb ; thats why I came up with the theory that there must have been an extra module and the wire ran there
devils in the detail guys

LB

why didn't I look when I was there !

Posted: Thu Dec 16, 2004 7:54 pm

Well, well, well folks! Very Happy

Tonight I pulled the carbon canister purge regulator valve plug while the engine was running and my "MIL" light came on! and stayed on! plugged it back in and the MIL light went out! Yell

Posted: Fri Dec 17, 2004 6:21 am

ah so ! excellent

what MY is your car ?
does it do it when fault the other sensors ?
if you dump your codes now is it still there , ie does your ECU have a permanent memory like 20v cars ?

LB
will try emissions equipment on a 20v

Posted: Fri Dec 17, 2004 9:32 am

Early 1994 build date.

I've disconnecting one of the lamda sensors with the same result. Have not tried to read the codes to see if the code has been stored as a past fault but I remember in the past when using my home made VAG-COM that when reading the codes an earlier code was stored that had been fixed. I would presume that the MIL would do the same.
With the MIL I think it references engine codes only so you cannot read fault codes connected with the ABS ECU like you can with the VAG-COM.

Posted: Fri Dec 17, 2004 9:40 am

thanks ; I am pretty sure that struikies NG engined car of the same generation didn't do this ; are you there struikie ?

LB

Posted: Thu Feb 10, 2005 1:19 am

Stupid question time again.....
Pin 24 on the yellow connector is the wire the power from the ECU is to go down to light the CAT light ?

ie I can pick on another terminal if the CAT light is used?

Posted: Thu Feb 10, 2005 9:22 am

Sure

, any unused bulb space can be used, I know on my coupe there was one for an electric cab roof Surprised

, use pin 26 for this location on the yellow socket Cool

.

Posted: Thu Feb 10, 2005 9:59 am

One step ahead this time !!
Found pin 26 to be common to all the lights on that plug so im assuming thats the earth/common whatever.
A bit more prodding found that Pin 13 on the Blue connector is the Cab Roof light on mine.
I dont want to know if my roof is coming off!!
thanks for the help for this eh.

Posted: Fri Feb 11, 2005 10:54 am

"one step forward, two steps back"
Always did like Paula Abdul.....

Just spent the last 3 hours pulling most of the underside of my dash apart!!
An hour to get the Instruments out and get a wire into the appropriate terminal, then get the ECU out (stupid place to put it!).
The rest of the time trying to figure out where the white wire already in the C14 hole goes. Disappears along with a black and brown wire into a plastic loom, loomed together with everything else from the ECU only to disappear into another dimension.
This is DEFINITLEY C14, connects the terminal 3rd from the end on the bottom row, I musta rechecked that 10 times! On the row marked 9 to 16.
Curiously, directly opposite on the plug is a terminal with no wire... C6.
Any one know if that loom of three is to do with the OBD? and the white wire is already hooked up to something diagnostic, or am I on the wrong side of the plug?

Cheers Fullas

Posted: Fri Feb 11, 2005 1:16 pm

Doonnzl, as your car has the 2.6 engine with different engine management (Siemens/Bosch I think?) then things could get interesting.

Does your ECU have four plugs that go to it? and looks something like below :

It may be the case that the c14 wire connects to the relay board under the instrument cluster, see this site for details of the Audi S2 that does have the code wire from the ECU but terminates at a plug on the relay board:

http://s2central.net/inst_clust_mil.html

I'm afraid you're pioneering for all those 2.6 'ers out there Rolling Eyes

Posted: Fri Feb 11, 2005 7:44 pm

Oh yipee....... Crying or Very sad

Well I'm this far...... That schematic does resemble the ECU that I have, with the exception of the 3rd/blue OBD plug ( the reason for all this in the first place! ). Cant see Bosch or Siemens or Hitachi on the thing, but it does have Hella on the inside.....?

In theory if that hole in the T5 plug is free, then I should be able to put the multimeter in there and test for continuity between the earth (or will it be power? ) and it when I switch the key on, if it is from the ECU on mine....

Posted: Sat Feb 12, 2005 12:47 pm

Hi Guys

I have tried connecting a wire to pin C14 from the ECU but instead of running it to the dash I connected it to a loose bulb and grounded the other side of the bulb dangling in the pasenger footwell.

Started the engine, shorted out the two connectors for three seconds but nothing showed on the bulb didnt light at all.

Car has been intermittently not starting and I suspecting the Cam postition sensor.

I used an old dash borad bulb think it was rated at 1.2Watts.

Any ideas as to what i ahve done wrong? Car is a 1992 Audi 80 2.8 V6 AAH engine.

Thanks

Tony