Busu

My Car: Audi a4 b6 2.0 2002

I've only owned it for 6 months now and in that time the transmission slipped a few times into neutral (suburbia & on the highway), there were no error messages or anything the dash still said it was in D - I had to cycle the engine off and on for it to fix itself. Outside of this the transmission never game me a problem.

However, in just the last couple of weeks it has been a lot worse and happens a lot more frequently, and today it did it again but this time the PRND lights began to flash. Does this pretty much confirm that its the transmissions ECU?

Other threads on the forums speak to how expensive these can be to replace and nightmares of replacements not even working just a few months later. What would you recommend?
Should I pick up a code reader and try and get something out of it? I've heard of companies that will rebuild you ECU unit and send it back with warranty? Are these a good cheap efficient option? Does anyone have any experience with one supplier that they can recommend? Am I just thinking of the worst and could it be something simple like it having low transmission fluid?

Just booked an expensive holiday about a month ago so I'm low on funding at the moment. I'm from Australia so I don't believe I'm entitled to the reimbursement resulting form the lawsuit against Audi in the states. Really regret not researching this car properly before buying right now, lessons learnt I guess.

Really appreciate any input or advice anyone is willing to share
Cheers

turbo510

Before condemning the TCU, some inspections are in order. First, you should obtain a code reader that can access the Audi's TCM. I have the commonly-used VCDS diagnostic cable, which will access every processor on the data bus, now around $200. It is well worth the money considering how much time/money you will save knowing what fault codes exist, plus the ability to operate many of the car's electrical items from your keyboard.

Next, check the fluid level. That has to be done correctly, and the method isn't obvious like using a dipstick on other cars. The fluid level is checked by removing a large plug from under the car, and the engine has to be running the entire time the plug is removed. If the engine is not started, or is running but shut off while that plug is out, a significant amount of ATF will run out. While the engine is running, much of the fluid is in the torque converter and the clutch circuits, and that's when the level is checked. The plug is not in the bottom of the pan, but hidden up in a tubular recess. The top of the recess determines the running ATF level, so when ATF is added, once the correct level is reached, any extra added will run out, proving the fill is correct. Whether you or someone else does this, read up on the procedure; the car also has to be level (within reason) and the ATF temperature must be within a range of 35C to 45C, I think. But if you have the VCDS scan tool, your computer will display the fluid temperature.

A1EK

Is your gearbox a CVT ? IF so then from my expereience you have a few options.

Option 1, If the PRDS lights are flashing then this is usually a sign that the gearbox TCU that sits inside the rear cover has a common fault with thin wiring on the circuit board inside becoming loose and detached. Do you find that reverse sometimes does not engage etc?. The flashing PRNDS lights usually indicate that communication to the gearbox ECU (TCU) has a problem and having the codes read will determine this. You may find that you can live with the PRNDS lights flashing occasionaly, if the reverse or other gears do not work thought you can cycle through the gears which usualy helps, but in time it will probably get worse.

Option 2. If after you have the codes read that TCU is faulty then you can be brave and take a chance to have it repaired, there are many places on the internet that do this service for around £100 / $200 AUS, however this is at YOUR risk and it may end up ruining the TCU altogether (This is what happened to me and I ended up needing to buy a new TCU which leads me onto option 3). If you are hands on you can remove the TCU yourself, I did this myself and took me about 3 hrs first time, but the second time only about 1hr.

Option 3. This is what I had to do, buy a new TCU and they are expensive ! £1100 or $2000 AUS plus 6 litres of oil and gasket, the oil needs to be installed when the car is warm at a specific temperature all in plus labour its about £1700 or 3000+ AUS.

Option 4. Scrap the car and save your money.

Busu

Thanks for the advice guys.

I'm not particularly the best at DIY so I've decided I'll take it to a shop to get the problem diagnosed for me.

If the TCU is indeed bad I'm going to give option 2 that A1EK recommends... except I'll have the mechanic take it out and put it back for me.. bba-remaninc on ebay offers lifetime warranty on the unit and some users on here have recommended them in the past.

Seeing the mechanic on Tuesday I pray it's just low fluid.

A1EK

I wish you all the best and hope that if you get the TCU repaired it will be okay. When I removed my TCU I found it had been repaired back in 2012 but 5 years later started to flash the PRNDS lights. When I opened it up inside I could see the problem of loose broken wires inside. I have added this link to help explain. Make sure you use a good company that can confirm they test the TCU after they repair it thoroughly and you should be okay.

david9999

Let us know how it turns out.
BTW, you did not clearly state if you have a CVT transmission or not.

Busu

Hi guys

Thanks again for your advice. Giving an update. Yeah it is a CVT David, sorry.

Mechanic read the codes, below are the results. He recommends I get the tranny serviced with a diagnosis of the current fluid and new fluid put in. However, my first instinct it to check out the sensor itself?? Also, after doing some more research on these forums people relate this error code to the TCM? Zzz guess there's no way to know for sure until I get the fluid looked at.



Busy period at work for me atm so I'm just weighing my options in the meantime.