Dommi3

I want to do an experiment on my A8 4.2 and swap my Ignition Control Modules to see if the fault code switches to a different side.

So far, I have a consistent misfire on only one cylinder (my #4). I already checked the coils, the spark plug connector wire and the spark plug itself. When swapped, all of those parts from the problem cylinder operated fine. Also, there is definitely current making it's way to my injectors. For now, I ruled out an injector as a problem because when doing a spark test, nothing was sparking on that problem #4 cylinder.

For me to conduct my next experiment I need to know where I can find the Ignition Control Modules? I have no idea as to where to look.

Any info would be helpful.

Thanks!

dommi3/Sausalito, California
1997 A8 4.2 Quattro
Silver/Gray
All Available Options

ricoblanco

If so, there are two, bank 1 and bank two. You will find them along the fire wall just above the windshield washer fluid reservoir. If in doubt, just follow the cable from the coilpacks and you will find them.

Dommi3

Yes I am referring to the Output stages. I have now heard these little items referred to as three different things, Output stages, Ignition amplifiers and Ignition control Modules. I really didn't know what to refer to it in this posting so I simply looked up the part number to see what most part sellers called it. Most called it an Ignition Control Module. Either way, I'm quite certain we're talking about the same thing.

Thank you very much, I now know where to look.

dommi3/Sausalito, California
1997 A8 4.2 Quattro
Silver/Gray
All Available Options

PaulW

As said, follow the wires.

Dommi3

Found them and they're right by the washer fluid bottle. Thanks for your help.

I happened to find the information below the dotted line on a VW website. Certain year Passats take the exact same ICM. The person that wrote the post very clearly explains how to test the part. I did the test just as described and low and behold, I had one bad pin in one of my ICM's just as expected. Obviously, the bad pin is what had caused no action on cylinder four exclusively. This information should probably go on Audi pages. I talked with a authentic German mechanic at the local Audi Dealer yesterday and he claimed this part has a high failure rate and is very commonly the problem part when there's consistent misfiring from a particular cylinder. Apparently it's very common in certain model A4's. Don't miss the details below which also includes the part number.

dommi3/Sausalito, California
1997 A8 4.2 Quattro
Silver/Gray
All Available Options

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Just finished up replacing the 4D0905351 ICM module on my daughters car
thanks to the fine information I obtained here. I thought I might try and return the
Favor by posting my experience with my diagnostic method for this module.
I've seen other sites that had information on this, but some were not clear or
missing important information.

Testing the 4D0905351:
1) Remove the two connectors from each side of the module. This is done by pressing down on the wire spring clip and pulling on the plug. They should come out easily.
2) Borrow or buy a handheld Digital Multimeter (DMM). They are available from Radio Shack or off eBay. The cheaper ones can be purchased for around $25-$30. It's a great investment!
3) Set the DMM for resistance measurement. Most DMM's today have auto-ranging so you need not select a range. If yours has a range selection choose the highest resistance range.
4) Connect the DMM's + (Red) lead to the middle pin on the modules five (5) pin jack. It is important that you connect the + lead of the DMM. These modules are made up of four power transistors which are polarity sensitive. Even though you are making resistance measurements the DMM does apply low voltage DC to the circuit.
5) One at a time connect the - (Black) lead of the DMM to each of the four pins on the four pin jack side of the module. Each pin should give a resistance reading of around 2.5M ohms (2.5 million ohms). Provide yourself a tolerance and say that 2.0M to 3.0 M ohms is OK. If any pins gives a complete OPEN or a resistance value other than that in our range that sparkplug/coil driver is bad. If you show all of them OPEN maybe you have the DMM connected backwards.

It seems like on the module the four pin jack has cylinder 1 as the pin closest to the letter B in Bosch. From there it just counts up by cylinders 2, 3 and 4. This is just a guess and I didn't officially check it out. However, my car gave the error code P0302 which is the ever famous cylinder 2 code. Sure enough on my module the second pin down from the letter B in Bosch gave me infinity ohms (OPEN) on my DMM. The remaining three pins read between 2.3M and 2.6M ohms each.

If you do replace the module as others have said make sure to clean the metal to metal portions on the bottom of the module and mount within the engine compartment. Add new white thermal conductive grease to this metal area before reassembly. This stuff is available cheap at Radio Shack or even at auto supply joints.

They will rob you if you try and buy one of these new at an auto supply house (Over $350 at AutoZone). The clones can be had for around $80 off the internet. I was lucky and got one from the local boneyard for $35 and its an original OEM Bosch from a 98 VW Passat. Some days I just get lucky. I did run a quick check on the boneyard module and sure enough all the four cylinder pins measured around 2.5M ohm.

Thanks again all who have posted here. The internet and these service support forums have saved me thousands of dollars over the past five years and I will always try and return the favors by posting my experiences.

NOTE: Don't use an old automotive analog resistance meter to do the resistance checks on these modules. In most cases they are not designed to make the high resistance measurements needed. Invest in a new handheld DMM as you won't be sorry.