i successfully changed my engine from 1.6 to 2.0 in a MK4 Golf 2001 the engine 2.0 start fine and run soft, but i am using the engine ecu from the 1.6. my question is if i can change the ecu from 1.6 to 2.0 using the wiring harness of the 1.6 engine?

  • Welcome to Motor Vehicle Maintenance & Repair! You definitely don't want to run the 1.6 ecu, because the tune is all wrong for the 2.0. The 2.0 is going to need more fuel to run correctly. If you don't, it will run lean and you run the risk of damaging the engine. You can try to put in the 2.0 ecu if you have it ... if the plugs don't match up, then the answer would be no ... I'd highly suggest you try to put in the 2.0 ecu, though, just to keep from damaging the new engine. Commented Feb 17, 2019 at 18:24
  • yes i know in this moment i am not using the car for this issue i will try some 2.0 ecu, thanks for your time
    – Chacaman
    Commented Feb 17, 2019 at 22:29
  • @Paulster2 is correct - you need the 2.0 ecu. What you should do is to check the pinouts for the connectors between the two cars - everything should be in the same place, and the components should be the same - tps, cps, map, maf etc etc
    – Solar Mike
    Commented Feb 18, 2019 at 8:45
  • @SolarMike thanks for your time and help!, i will test to day some 2.0 ECU
    – Chacaman
    Commented Feb 18, 2019 at 11:35

1 Answer 1


Welcome to MVM&R! As you've already found out, the wiring in the car allows you to start the 2.0 engine with the 1.6 ECU. The main reason for this is that the wiring loom is effectively the same across most of the Mk4 Golf range. You will find that pretty much everything between the 1.6 and 2.0 will be plug-and-play with one possible gotcha. In 2001, the Mk4 Golf was face-lifted. Externally you'll see little change between the old and new version but mechanically and electronically, the two vehicles have some key differences.

Ideally you want to switch to a 2.0 ECU, or at very least have the 1.6 ECU remapped to suit the fuel and ignition demands of the new engine. You will however find that if you simply plug an ECU from a 2.0 into the car, it will not start. The inbuilt immobilisation in the Mk4 ECU ties the ECU, clocks (i.e. instrument cluster) and ignition key together. If you have all three from a 2.0 and it is the appropriate vintage (i.e. from a pre or post 2001 car depending on what you have) it will go in and work.

Alternatively you can either have the immobilisation defeated by sending the new ECU to a specialist or you can have a specialist program your new ECU to your existing instrument cluster and code in a brand new key transponder chip. If you do go this route, you'll encounter the terms IMMO2 and IMMO3, this simply relates to the immobilisation system present on the car.

So, in answer to your ECU question, you either want a native 2.0 ECU or have your 1.6 ECU remapped for the new engine. You should not use the unmodified 1.6 ECU with the 2.0 engine. As for loom, Volkswagen have been very good at standardising wiring looms since they introduced their CE1 standard back in 1985. Yes, the 2.0 ought to plug straight into the 1.6 loom but just ensure that any parts vehicle you use is from either pre-2001 or post-2001 depending on the age of your Golf. If you mix and match pre and post, they will generally still work but you may find yourself chasing odd issues.

  • thanks for your time and your answer my friend have some ECU 2.0 and in this moment where testing all IMMO versions
    – Chacaman
    Commented Feb 19, 2019 at 20:45
  • Hi, guys new update i test some ecu 2.0 the same plug the immo is version 2 whiout pin, i test 3 ecu and on all ecu i have the same error :P1579 - 35-00 Adaptation Not Started and P1565 35-00 Lower Stop Not Reached i think the problema is the ECU Coding i have the same problem in the 3 ecu
    – Chacaman
    Commented Feb 23, 2019 at 18:14
  • ok, swap succesfully whe have to change som few pints on the wiring harnes now my Mk4 Is full 2.0 Engine and ECU thanks all for the help
    – Chacaman
    Commented Feb 27, 2019 at 20:23

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