Sunday,21-April-2019

VAG 1.6 TDI CAYC engine EGR issue - and perhaps solving..

EN

HI!

In that topic will write little about that so much discussed in the internet EGR issues with VAG 1.6 TDI CAYx engine.

How to clean - you can already find lot of topics online. What are the common issues:

- broken plastic wheels in the control unit

- clogged valve

- on the control arm bearing pin get out and limit the move or the bearing itself get bad..

For all that there are plenty materials on the internet.

I drop onto some interesting article here: http://jestineyong.c … k-on-1-6tdi-engines/

I end up following that write up for while but didn`t work so well for me. If you still follow let me explain.

In the car of that particular example have been used a lot of liquid for cleaning the EGR on place, but still maybe the problem was more with the software than the EGR itself.

First, here is the picture of the issue(used VCDS for check up):

egr_0.jpg

I mark the important things:

- upper limit is 3.99V

- lower 1.00v

What that mean? There is electric motor which spin one teeth wheel. To that half wheel is attached the valve itself.

On the same wheel there is permanent magnet(the ring):

egr_6.jpg

that magnet, been red by Hall effect sensor on the motor driving board (that small black IC element)

egr_7.jpg

the magnetic field control the output voltage via that sensor. In other words, the ECU “know” where that valve is positioned. Here, the problem was that the stored minimum value(valve closed) was 1 volt, but now show 0.67V

Then the ECU “think” that the valve is “over” closed, or say defective and put the car in limp mode.

In that website mentioned before, the autor suggest to create voltage divider and actually to “add/boost” extra voltage to the present one and to lie the ECU. That was great idea at first, but didn`t get me to solve the problem.

Next - remove the motor:

egr_1.jpg egr_2.jpg egr_3.jpg

You need long TORX. Also, keep in mind that the removed bolts can drop easy and get lost - so be careful and also bare in mind that is much more easy to remove the power plug when the motor is out.

That been said and the motor removed, I decide also just in case to check the power supply, GND and signal cables. Here is how:

egr_4.jpg egr_5.jpg

- need to gain access to the ECU. In my case that is touran T1, so can`t say that same diagram will be suitable for SEAT/SHKODA/Golf… The plug I need is T60.The smallest one. The other is 94pin. To read the chart, you see for example T60(54) > that mean in plug 60 pin, select 54-th.

- then on full contact(but not started engine) measure the motor plug for all 5V/12V/GND. If they are present - good. Then check anyway the cables for free signal flow with multi-meter. Again from the diagram above you can see which pin on the ECU side do what what.. (for our purpose).

Also, 5V power supply come via some points where interfere with other sensors. If you get unstable or “jumping” readings, that must be fixed first. Here, in that case all seems fine.

- next in the list, was that resistor divider way. Calculate what I need as value and give it a shot:

egr_8.jpg egr_9.jpg

The idea was to boost the output signal taking power from the supply 5V. Fit all back on place and start the car.

After DTC errors was reset, the car start smooth and let me to kick it ass down as high as 4-5 000rpm..

Good.. but not so good. Like the lambda loop in petrol cars. In diesel engine the EGR start to be active after some time after start and some temperature rise.

Or to put in perspective - when the car rise the engine temperature, then the EGR kick in.. then the limp mode come again… Huh..

egr_13.jpg

As you can see now the readings was 1.2V.. instead calculated 1.05V. That is problem number one. Two, the ECU expected when EGR is let`say 25% to be 430mg/str air measured via MAF.(numbers are for pure demo purpose, not the actual).

Or the proportion air moved via EGR to be reduced from the MAF readings.. Well, it red 420-410.. or not exactly 450 what it expected to be. And .. again limp mode: visit the workshop..Yeah.. right.

So now the actual measure and the requested went far misaligned. That require calibration. In VCDS menu, there was that option: Adaptation of EGR.

egr_11.jpg

If you push it on idling running motor, it will rise the RPM to 1500 and.. even you try to throttle it to 2000-2500 and release the gas, will come back to 1500 but.. nothing actually happen. Unfortunately, can’t edit the values straight forward as in the petrol EGR cars. That was bad.

On car with engine OFF.. Nothing. And there is so far no instruction or help in the WEB how actually you can do that “adaptation”.

Next in the list: reset. What more we can damage right?

From the same picture with the list, you can see - Erase static memory. So, I push it, and next was Resetting of… (marked in red, second line).

Maybe that second one is not good to push just right that, but after some city driving, then highway… the car actually didn`t show any strange behavior. Perhaps went to some kind of adaptation cycle.

After trip end,and new check up on the ECU codes, it said: NONE. The new stored values was: 1.2V min, 3.99max.

Need to mention, that when the motor is removed you need with finger to try that valve half wheel if you can move it free. If not, then you need to take the whole unit down.

Now, two , three weeks later, still all seems fine and the car run smooth.!

Maybe, before you start doing that hardware hacks or buying new EGR(or original one) you can try that way (reset - drive) and see if that fix your issues. Of course, I presume you can try to clean the EGR on place before doing that procedure.

Good luck!

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