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Exhaust Gas Recirculation EGR System Hack on 1.6TDI engines

By on January 27, 2017
egr system circuitty










Today I will discuss about a very common problem on now day’s modern car’s so called Exhaust Gas Recirculation system or in short EGR. I got a Skoda Octavia II 1.6TDI-CR engine code CAYC which was suffering on power leak, service mode or LIMP mod however, “Check engine” was on etc.

Mechanics told to the customer the EGR system should be changed, but that is a very expensive story for the customer. Then they told does some “hacker” should the EGR system disarmed ( so called EGR OFF method ) from the system so that system would no more be in an active working condition, but the error code would never be logged by the ECU etc. In my meaning that technicians only part changers and not pros.

I decide to check what is going on and why should somebody turn off a system in a car if some manufacturers are made that for some reason.

So, here is the repair stuff by me:

The EGR system on this type of engine is not as complex as it looks like. Here is a picture and a *design view of the unit.


car egr system hack

On this engine a P0408 DTC was set, which means on a simple language the EGR valve is too much closed, or in technical meaning the signal to the ECU is very low actually it is out of range.

What this mean, on this unit the common DTC’s are:

P0408 – signal too low, out of range

P0403 – signal too high, out of range

P046C – which means the EGR valve is not in a position in which it should be.

Please note that I declared these errors on a very low level so people who are not pros or technicians can also understand what this DTC’s means.

In profession technical doc’s these DTC’s are more specific and precise declared.

Here are the pin outs of the EGR connector:

Pin 2 and pin 6 are the PWM wire who powers the DC motor, where pin 2 is GND, pin 6 +12V.

Pin 1, pin 3 and pin 5 are the signal pins.

Pin 1 is the reference voltage from the ECU and the value must be 5V.

Pin 3 is the signal ground

Pin 5 is the EGR valve position value which must be between 0.71V and 4.01V.


0.71V means a closed EGR valve.

4.01V means an open EGR valve.

Everything between 0.71 and 4.01 is the position of the EGR valve which is returning to the ECU.

Checking the EGR for electronic failure:

  1. Let the EGR unit on the car as is.
  2. Check the pin 2 and pin 6 with oscilloscope for 12V PWM signal until the car key is turned to ignite position but don’t crank the engine.
  3. Check with voltmeter the pin 3 and pin 1 for 5V until the car key is turned to ignite position but don’t crank the engine.
  4. Check with voltmeter between pin 3 and pin 5 for 0.71V – 0.9V until the key is tuned to ignite position but don’t crank the car.
  5. Unbolt the EGR motor and check if the valve is moving freely by turning the half gear by hand.

how to hack egr system

In my case in the ECU was stored the P0408 error code.

Until I checked the signals as I wrote I realized does the signal between pin 3 and pin 5 are low which was around 0.59V. This triggered the DTC error P0408. There were also no trapped mechanical parts or even no clogged parts.

Why have I a low voltage in a zero position of the EGR valve?

I assume because the age and millage of the car. The mechanical parts got some space after years of friction and this would explain a small deviation in the voltage. I have to get back a 0.71V to the ECU when the EGR valve is in zero position.

What I did was actually make a small voltage divider with two resistors and sum that voltage with the output voltage which tells the ECU the position of the EGR valve. In my case, I measured a voltage of 0.59V but I need 0.71V. So I must add something around 120mV.

I have a reference voltage of 5V on pin 1. Adding two resistors in series so does it gives me in the midpoint a voltage of around 120mV. Then I cut the trace on the PCB where the output pin was. Now one end of the resistors was soldered to the pin +5 and the other end of the resistors was connected to the pin5 on the IC. The midpoint of the resistors was connected to the ECU or to the pin 5, so I got a new value to the ECU which was around 0.72V.

Here is a picture about my hack.

how to fix car egr system

Actually I summed the two voltages and so I got a desired voltage around 0.7V.

What you have to worry about this hack is that, does the value of resistors what I used is not specified to all situation on all EGR problems.

To specify the value of the resistors you should first check the difference in the voltage between the measured voltages on the EGR connector pin 3 and pin 5 and there must be a voltage which is 0.71V.

I also tested this on two other cars with the same symptoms and all of them had a lover voltage but not the same low voltage. One of them had around 300mV the other had around 630mV etc. and in relation of the differential you have to calculate value of the voltage divider with two resistors.

Before I made this hack, I simulated this also on my computer in my favorite circuit simulator. NI Multisim, of course there are other nice simulators too. Here is my simple’s circuit from my simulator:

egr system circuit simulator

Here is the formula for calculating the voltage divider resistor values:



Vout = should be the searched voltage which is 0.71V

This tutorial will save money for the customer and lot of repairing time for the technicians who repairs the car, but you should know does, this type of repairing is not usable and without success if the EGR system is full filled with dirt and if they are some failed mechanic parts and the EGR valve mechanism can’t move freely. In that case you have to change the mechanic mart too.

* The design view picture was taken from the SSP 442 training document made by VW AG.

I hope you enjoy this tutorial and will save lot of repair time.

This article was prepared for you by Christian Robert Adzic from Novi Knezevac-Serbia.

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Note: You can check his previous post in the below link:




  1. Bulent NUR

    January 27, 2017 at 5:45 pm

    So many thanks.

    • Andrew F. ali

      January 30, 2017 at 11:37 pm

      GOOD JOB!!!....I don't know much about Auto-electronics....but reading your article...I feel a great sense of appreciation for your work. Thanks.

  2. Albert van Bemmelen

    January 27, 2017 at 6:01 pm

    Thanks Christian, you've moved from Eeprom hacking to Car hacking. Very Impressive!
    I do not own a Car nor a OBD device, so it is all unknown territory to me. But your information could always be of use to someone I know who fixes cars.

  3. Ulises Aguilar Pazzani

    January 28, 2017 at 10:04 am

    Mr Christian , happy New Year , nice repair something new great

  4. Parasuraman S

    January 28, 2017 at 1:46 pm

    You have the deep knowledge that of a Design Engineer! Why don't you make a data bank of such common electronic problems in cars and develop a replacement kit which can replace the defective circuit with minor modifications? You can not only earn but also help car owners from spending heavy amount on expensive replacement of its whole unit in place of minor rectification that set it right!

    • Chris

      January 30, 2017 at 7:05 am

      Thank you for your support my article.
      You know, I've thought about it to make such of data bank with nice replacement kit's but that would be very hard to make it universal.
      I also found some "universal" replacement kit's on the internet from some
      peoples who sale it but that won't actually work in many case, but in some situation that would work.
      Lets say, in the situation of this article, I would never know what voltage divider I should make for the customer until I know what is the output voltage of the positioning IC. In that case I would sell the customer a not working part. The customer would not be happy.
      But! I think, if I release documents about the problem, with facts on blogs like this thanks to Mr. Yong and other blog holders, the mechanics and electronic technicians could read and implement it and make the customers happy.
      I earn lot other ways from articles like this, because it is in front of eyes of the readers of the whole word, and people can check my writing and comment it. Until I get positive feedback from all of you I know I earned more then money, I earned reputation and I now I done my work in a good way.
      Some times the customers of the car and who would be a potential buyer of my kit's should have some knowledge about electronic and information technology so he could make a measurement and made the repair...
      But of course your idea is well come by me and I'm always thinking about how to make that replacement kits user friendly and working.

      Thank you for your time.
      My best regards.

      • Vineeth reddy Vangoor

        April 11, 2019 at 6:33 am

        Hello , I want to know more information about egr valve . Can you tell me how egr valve function along with PCB , Ecu, Lin , flap , and transmission , battery appears along the system . How it controls and implementation of function and by steps . Please help me about solution please

      • Quinta

        June 7, 2019 at 4:16 am

        BONJOUR et merci pour le tutoriel,
        J'ai suivi votre méthode, et testé le diviseur de tension j'ai obtenu 0,72v, mais une fois sur le circuit je n'obtient pas cette tension j'ai maintenant 4,3v entre la sortie et la masse. Est ce que c'est normal ?
        HELLO and thank you for the tutorial,
        I followed your method, and tested the voltage divider I got 0.72v, but once on the circuit I do not get this voltage I now have 4.3v between the output and the mass. Is it normal ?

      • Quintana

        June 7, 2019 at 7:34 pm

        I wish to have your email because there is a mistake on the assembly and I would like to discuss with him.
        I found 4.3V not 0.71 Bitwin pin5 and gnd
        thank you in advance

  5. Yogesh Panchal

    February 1, 2017 at 4:56 pm


    Thanks for informative article

  6. Miguel

    February 6, 2017 at 2:36 am

    Excellent note, it will serve to do the same to my hue (daewo) that has the fault P1403, already cleaned the valve and continues with the same error, thanks, greetings.

  7. ombra32

    February 23, 2017 at 8:07 pm

    Very impressive!! Like always...

  8. Siavash

    August 31, 2017 at 9:25 pm

    You are a legend ive been looking for this information all over the Internet for a month now so i can do this. Where did you find this information about the reference voltage and minimum and maximum values?
    Thanks alot salute from new zealand

  9. SEAN

    January 19, 2018 at 5:53 pm

    Hi great right up. Can you tell me if I have 0.04v between pin 3 signal gnd and pin 5 signal what mv of resistos do i need for each pin

    • Chris

      January 30, 2018 at 1:59 am

      Thanks for supporting my article.
      So, for first.
      Please let me know what voltage you need?

      If your egr is another type or another type of car, maybe your voltages are different.
      So, you need to figure out what voltages are your min and max.
      Also you must need to know what is the cos of your fault...

      My best regards.

  10. Ľubomír Baran

    February 7, 2018 at 8:24 am

    ***Vout = should be the searched voltage which is 0.71V

    This is not good... i guess this Vout should be 0,124 what is yours added voltage. Or formula for 0,71=V2*(R2/(R1+R2)) + V1; for your picture. Am I right?

    But appreciate this really helpful article, it helps a lot.

  11. Paul Doe

    November 16, 2018 at 2:26 pm

    Hello. I got error P0403, replace the old EGR motor only(wahler) with one newer(but second hand - BorgWarner) and now I got error P046C. It is possible to be a hardware problem with my EGR? I checked voltage wit VCDS, and the old one(with P0403) has values between 0.9 and 3.4, and the new one has values between(1.2 and 3.9). I dont know what to belive... And it is difficult to change the entire EGR system, because its location is not easily accessible.
    Any opinions?

  12. SK

    April 14, 2019 at 6:32 pm

    Hello, and many thanks for the great write up..
    Although there is plenty useful information can say it doesnt work exactly that way.. Why? Let me explain:
    I got to the very same problem on 1.6 TDI CYCA engine. Values stored in the ECU was 1.0v for min, and 3.99 for max. The EGR error was that current value of 0.667v is out of range it it give EGR -23% value.
    Then I calculate what can be the closest resistor divider values and in my calculation that should of giving me about 1.01-1.05V. So good to go.
    Not exactly. The engine start, it show me 1.05-1.1V, engine error disappear, no limp mode present, can push it over 3000rpm..
    That was until engine get warm..
    The EGR tables work : less or non on really cold engine. On warm engine but accelerating - stay closed. But on cruise speed problem began. Again went into limp mode this time with air mass out of tolerance.
    - Why?
    Because let`s say ECU knows that in 50% EGR position should be 400mg less air measured via MAF. Yep, but now we "cheat" the value and even the magnetic sensor value show almost right, the AIR mass via that valve is different and voila - Engine failure: visit workshop and limp mode..
    So, again in square one. Via VCDS EGR adaptation actually only lift engine RPM to 1500 and nothing happen. After that, I decide to try something more radical:
    From the same VCDS menu I choose: erase static memory, and then Resetting of learned values of average quantity adaptation.
    After that, engine on.. still no lamp or limp mode.
    City normal drive and then 80-100km on highway.. Still good.
    After few pull ups on low gear, return and connect on VCDS again.
    VEGR_BOL now show 1.2v and VEGR_TOL: 3.99v. Or in other words it accept the new value and so far second week car run smooth and no error appear..
    Maybe before that hardware modification, is better to try to clean little with sprays on spot and then re calibrate the values..
    Hope, that is useful to someone else.
    Good blog by the way 😉

    • Radu Nicolae

      April 27, 2020 at 7:53 pm

      Hi, how did u managed to reset learned values. I tried but nothing happens, can u pls give us more details, I'd rather prefere the soft approach instead of modifying the PCB.

  13. Christian Adzic

    April 16, 2019 at 2:54 am

    Thanks for supporting my article and for the nice explanation how you solved your problem. I give a like to this explanation.
    Almost every time when any problem occur I try to do the basic thinks like you described.
    Check for the values, clean (if possible/need), try to reset/calibrate the unit.
    So far so good.
    In this case, I can't really remember every detail of the repairing because that was almost over 2 years ago, but I can remember when the mechanics guy asked for my help, I saw the EGR valve unmounted and cleaned well.
    What I realized was the old trace of the original position of the valve and a "new" trace of the valve what was more deeper in the housing than the old one. That trace was maybe a friction of mm but enough to make such of problem.
    After several try to calibrate the EGR through VCDS I got the same error immediately after the car was started even on a complet cold engine.
    Then I had access to a new valve where I could clearly see the mechanical off position on the old valve.
    I got also an information from the official VW repair shop does these type of engine have some strange problem and even fitting a new EGR to the car can not guarantee the repairing, because of some software problem.
    I know, maybe that is not so true as they told but they warned the owner for some reason...

    I never figured out why the calibration didn't solved the problem in my case, but after the mod I made everything was fine even on highway, city driving etc.

    The car is still driven with the mod.
    After reading your explanation, I came to a maybe possible solution why we have different repairing tasks. Maybe in my case the EGR was so bad does the max negative position of the EGR was not acceptable by the ECU firmware, I don't know if any of that kind of restriction are implemented.
    I was also thinking about to make a remap of the ecu and make some small tweaks to the ecu map but this mod was my plan A if this will not do the trick
    I would maybe move to plan B and remap or I don't know...
    However,that car and maybe 2 or 3 other have that mod made by me and they still on the road for now. Even after 1-3 years.

    Glad to see new solution on this blog like yours and I also like to discuss so we can pus forward in our repairing knowledge.

    My best regards.

  14. Andrey

    November 17, 2019 at 6:06 pm

    Golf 6 2010, cayc 1,6 tdi.
    Voltage betveen 5 and 3 pin was 0.7v, but every engine start was with flashing "spiral" and "check engine".
    I raized voltage betveen 5 and 3 pin to 1.3v, cleared all errors and went for a ride about 50 km.
    There was no "spiral" and "check engine" during the ride and no errors on the computer.
    Many thanks to an author!

  15. Khalid

    November 25, 2019 at 3:12 am

    Hello Christian and thank you for very good info.
    I have the same car Skoda octavia 1.6 tdi 2012 and i got error code P046c only when the weither is very cold let us say 0 degree or under that! when it is warmer i get no error code att all! what do think can be the reaseon?
    Thank you in advance.

    • Mirko

      April 7, 2021 at 7:22 pm

      Hello, I've read now your comment, I have exactly the same problem. P046C error on cold start below 5°C... Have you found a solution? My EGR is brand new (1000km of life).

  16. Evis

    April 4, 2020 at 3:16 pm

    Thanks a lot Christian Adzic, your post are very helpful for everyone

  17. RudLee

    November 16, 2020 at 10:43 pm


    I have some strange things going on.

    Between pin 3 and pin 5 multimeter is showing 0. Tested with 2 different multimeters and both the same.

    i have constant CEL about P0408 error and sometimes it goes away for 1 -3 days sometimes it stays only with cold engine and now it is constant error mentioned above.

    Do you have by any chance wiring diagram and pinout from ECU to G212 valve? maybe some wires are broken been searching for two days with no luck!

    Really like DIY stuff but now i am backed up in corner and its its hard to drive 1.6tdi in city with emergency mode on.


  18. Corse

    February 25, 2021 at 5:32 pm

    Christian, la perte de puissance vient de l’actionneur du RGE entre la cosses 2 et 6 faut que sa une résistance 0.0 ohms passer cette valeurs le défaut p40800 apparaîtras
    Christian, the loss of power comes from the RGE actuator between terminals 2 and 6 must have a resistance of 0.0 ohms to pass this value the fault p40800 will appear

  19. FK

    September 16, 2021 at 10:48 pm

    Hello, great artical.
    Can this trick be used with blanking EGR?


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