GOLF MK6 EGR

My GOLF MK6 suffered from the EGR syndrome. On this page I will try to explain everything I did to fix the problem and avoid extensive maintenance costs to replace the valve. I will also try to identify the underlying problem with these kind of valves failing at different cars.

As far as I know, Volkswagen only covers this repair if the car is within warranty period, otherwise they will verify the customer maintenance schedule and offer something between 70% or 30%.  This type of repair costs between 700€-1000€ in Europe, and they replace the whole valve assembly by a new one, in fact, the job is specified as an 8hour job but as I suspect takes a little bit less.

Another VW scandal? 🙂

The valve is driven by a small DC motor (white gear) and is being monitored by the Melexis 90316 Triaxis IC. This IC monitors the magnetic shaft providing feedback for the ECU regarding its position

triaxis
Magnetic shaft schematic
img_20161127_140421
EGR Motor assembly

The ECU reports error when the valve feedback is off range, 1-4v, so I went to further check the output.

I’ve used an Arduino with an 16bit to Digital Converter (ADC), the default 12bit converter is not enough for an 14bit output supplied by the IC.

img_20161128_214234
Arduino monitoring EGR
img_20161128_214103
Detail of the ADS1115 ADC module
img_20161128_214052
Old Arduino version

Firing up the module and monitoring the serial output, we can clearly see the closed output value, ~0,6v, is way off range. The car ECU has a mecanism to calibrate the readings, but I’m unable to do it manually using VCDS, I suspect that if the calibration procedure was done the car will not report the error.

code
Monitoring the valve output

This IC has a programable scaling mecanism that allows output ajusting, that is, if we can adjust the output we could overcome this problem.

clamping
Output clamping

As the Melexis90316 requires a proprietary programming tool, and I can’t have that, we may use the Melexis90363 as an “open-source” alternative.

Let’s try to:

  1. Program the new IC;
  2. Replace it by the original one;
  3. Inspect both outputs to low precise control over the valve.

img_20161127_140737

EGR PCB with Melexis 90316 removed

To be continued…