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Audi 80 B4 ECU Chip Fitting Guide

Updated on June 8, 2012

Audi 80 ECU Chip Installation

This is a simple step by step photographed guide on how to remove the ECU from your Audi B4 model. I have used my 1995 Audi 80 Avant estate for reference which I was planning to 'super chip', however due to incompatibility issues I can't yet fit my chip but decided to write this guide anyway.

Benefits of fitting an upgrade chip

Fitting an upgrade chip into your car's ECU is not just for performance and racing. A good 'super chip' will also smooth out the rev range and improve fuel economy as well as give a little more power. It is a very straight forward modification and will only take about 30 minutes to fit requiring no specialist tools or equipment. The process is generally the same for most vehicles apart from specifics on the exact location, however this information should be suitable for Audi and VW drivers as the parts are very close in comparison.

Audi B4 Avant

Audi B4 Avant
Audi B4 Avant

Disconnect the battery

Firstly and most importantly you will need to disconnect the power to the car by removing the negative terminal of the battery. You will need a 10mm spanner for this although some vehicles use a 12mm bolt for the battery terminals. Disconnecting the negative side is safer as it avoids any shorting that can happen with the positive terminal. Im not usually one to disconnect the battery for electrical jobs, but as this is the brain of the car and things can go wrong, better safe than sorry.

Passenger footwell

Moving over to the passenger side footwell you should notice a panel that sits underneath the glovebox which is used to hide away the external cabling and vent pipes that run along the firewall. The ECU is tucked away behind the glovebox but is easily reached from this panel which is much easier to access and remove. Mine had a couple of 10mm bolts holding everything in place but I imagine that these were fitted after the originals were lost at some point, so check the underside and make sure you see what exactly is holding your panel in place.

Remove the panel

Once you have removed the panel hiding the cables and bottom of the ECU (just visible in this photo), you will notice the large white plastic clip that holds the panel in place with a slot. This plastic clip will need to be removed as it obstructs the ECU from being slid downwards. A flat head screwdriver is the best tool for this job. The plastic clip is held in on a stud head fitted to the firewall and can be levered forward until it comes away. Don't be frightened of giving it some force as it shouldn't damage anything and the clip should eventually pop off.

Remove bolts and plastic clip

Place the bolts and plastic holding clip to one side for refitting later. I took this picture so you can see how big the clip actually is and what type of bolts is being used to hold my cover panel in place.

Drop down the ECU

Now you have full access to the ECU it is a case of gently rocking it back and forth while pulling downwards to free it from its holding. I found that my ECU had 2 metal clips, one at each end, that neatly clipped the whole unit in place but meant it was a little tricky to remove when I had no idea how it was meant to come out. Once freed it made total sense for refitting later.

If you notice I have not yet removed the ECU cable connector as I wanted to know I could extract the ECU unit first. The cable is very easy to remove as it uses a sliding plastic clip which locks the cable to the ECU. To remove just pull the end piece along and the whole lot will lift off, if it doesn't work try pushing rather than pulling.

Now you can detatch and remove the ECU unit from the car and take it inside to strip down. I wouldn't advise doing the next part outside where you are working on the car as its something that needs patience and calmness and a table to work on. In the past Ive done these sort of jobs as I go along and end up wishing I had taken a little more time and got comfortable first.

First thing you will notice when you get the ECU unit inside is the metal plate that it is attached to. There is a single cross head screw holding it down which you can just remove and then slide the plate away from the two guide pins at the other end.

Open the ECU casing

My ECU which is the Siemens model has 4 torx bolts at the end which keeps everything locked together, so now is the time to unscrew them. They shouldn't be security bolts so should be no problem to take off, but if you have problems, or don't have a torx head screwdriver then a small flat head screwdriver like a watchmakers tool should be fine to fit in at opposite ends of the star head and be fine to remove the screw with so long as you don't cause any damage.

Once you have exposed the ECU circuit board you will notice a small aluminium box cover which the chip sits behind. Turn the ECU board over to look at the back and you should see several clip ends on the back plate, they are very flexible and thin and can be lifted with a fingernail rather than a screw driver. You must remember to be careful here as any damage caused to the circuit board could stop the car from being started again (ever!). Once the aluminium cover has been removed from the back turn it back over and the front cover should pop off in a similar way. You should now see the exposed chip.

The ECU chip

The ECU brain or stock chip is the oblong one on the right which is the only one that is removeable as the square chip is soldered into place. Simply prise it upwards from both ends being very careful to try to lift it evenly to avoid bending any of the pins on the stock chip.

Refit your upgrade chip in the holding slot and put everything back together. Refitting is the reverse of the removal process and will be simple to do at this point.

Siemens ECU information

Siemens ECU information
Siemens ECU information

Bosch vs Siemens

To my knowledge there are only two main ECU manufacturers for the Audi 80 B4 model.

Bosch Digifant ECU Part Number: 5WP4058


Siemens 5WP4 174

When ordering your chip make sure that it is the one that corresponds with the ECU in question as they are not compatible with each other and can cause a lot of headache and problems. If you are unsure don't do it.

Please feel free to leave your comments or thoughts here. If you appreciated the information on this page, you can thank me by clicking on the 'thumbs up' icon.

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