Vehicle make: Volkswagen Model: Bora Year: 2004

Issue: Swapped the 1.6L for a 2.0L. No programming of the ECU was necessary neither was a change of ECU necessary until vehicle started misbehaving - that is to say, vehicle would refuse to start. Diagnostics pointed to no communication with the original ECU. Subsequently the ECU was replaced. This ECU replacement remedied the problem. After a while the new ECU itself started having problems. Replacement ECU is meant for a 2.0L engine from the VW stable.

Former ECU code: 06A 906 033 BN Current ECU code:06B 906 033 AD

Problem: The car starts but throws a bunch of codes:

  1. 17524 Bank1- Sensor1, Heater circuit, Open circuit (P1631)
  2. 17526 Bank1 Sensor 2 Heater circuit, Open circuit (P1118)
  3. 18014 Rough road spec engine Torque ABS-ECU, electrical malfunction in circuit (P1606)
  4. 18020 Engine control module, incorrect coding (P1612)
  5. 18039-Accelerator position sensor G79, signal too high (P1631)
  6. 18088 Reset-resistant limp home (P1680)

Questions: Is this swap recommended? Is it common?

Can the ECU that came with a 1.6L control a 2.0 engine? Should we get another ECU with a part number same as the first?

MOST IMPORTANTLY How do I get this vehicle to run properly?

Details of the donor vehicle of the new engine Details of the donee vehicle

  • Which question do you want answered? Is it recommended? or is it common? or is your advice in order?????
    – Solar Mike
    Commented May 19, 2018 at 16:54
  • Any or all the above. They want the vehicle to run properly. And I want to know if given their investment we should go ahead with modifying vehicle as it provided it is not an elephant project, and if is, then had better get the original engine and ecu Commented May 19, 2018 at 16:58
  • It's a bottomless pit project - your edit does not show any of the codes you promised...
    – Solar Mike
    Commented May 21, 2018 at 6:45
  • It actually does, VW has their own internal designations for problems with their vehicles if you use their diagnostic tools as opposed to using generic scan tools. I listed 6 trouble codes Commented May 21, 2018 at 13:58
  • Well, one seems to be that the accelerator pos sensor is the wrong one - is it original ie for the old engine...
    – Solar Mike
    Commented May 21, 2018 at 14:06

1 Answer 1


It would help if we had the engine codes and the two ecu types (EDC15/16, Med7/9 ect) and the fault codes that are present but here goes:

It sounds like the engine was swapped complete with the correct engine wiring loom for that engine and the correct ecu for that engine has then been unlocked (had the immobiliser removed). If this is correct there shouldn’t be many fault codes concerning the running of the engine. Any fault codes will probably be due to lack of comms with missing modules/ecus that the donor car had that the current car hasn’t.

There may also be fault codes in other ecus/modules due to not communicating with the engine ecu properly.

VW engine conversions are fairly common practice (in UK and Europe anyway). There are two options depending on what codes you have. Get a decent tuner to delete the present fault codes in the engine ecu, I say decent tuner because there are many ways to delete fault codes in the firmware file and you don’t want to end up with the ecu not reporting any fault at all as damage may occur if you don’t know about them and diagnosing faults would be a nightmare.

Get a tuner or decent auto electrician to ‘virginise’ the engine ecu and then reprogram it with VAG-com. This may or may not be possible depending on ecu and engine numbers.

So for anyone with experience with VAG vehicles and ecu tuning this is a very easy task if you know your way around the flash file.

Update based on your additional info:

Using the clocks and additional modules from the donor vehicle is a really unprofessional way to get the engine running correctly. This is really a simple task for any decent tuner or specialist auto-electrician. The engine ecu just needs reprogramming and unlocking properly.

17524 Bank1- Sensor 1, Heater circuit, Open circuit (P1631)

17526 Bank1 Sensor 2 Heater circuit, Open circuit (P1118)

Both of these should be easy to rectify, you need to test the wiring and confirm if the O2 sensors from the donor vehicle have been used or are the same. The fact that both sensors have faults seems to suggest that the wrong sensors are being used or there is a missing live somewhere.

18014 Rough road spec engine Torque ABS-ECU, electrical malfunction in circuit (P1606)

18020 Engine control module, incorrect coding (P1612)

This is because the ecu is coded for auto rather than manual. This can be done in two ways, use VAG-com or similar high level diagnostics to reprogram the ECU to manual and while your at it you maybe able to reprogram it to the ABS and other modules in the vehicle, you may need to have the ECU 'virginised' first. Or have the ECU reprogrammed through the flash file by the tuner or person who is unlocking or tuning the ECU.

18039-Accelerator position sensor G79, signal too high (P1631)

Should be as simple as the wrong accelerator pedal. Confirm that the connectors are pin compatible and then swap the pedal.

18088 Reset-resistant limp home (P1680)

This is due to the incorrectly coded ECU. This is usually a sign that the immobiliser has been poorly disabled and they haven't corrected the checksum. But it also appears when the ecu is incorrectly coded which yours is, so I would have the ECU coded or tuned first as this code will then probably disappear.

So you really have nothing to worry about, you need to do the following in this order:

  1. Check the O2 sensors & wiring, swap the sensors if necessary.

  2. Check the pin compatibly of the accelerator pedals and swap them.

  3. Have the ECU reprogrammed either through VAG-com or my preferred option would be to have a professional ECU tuner swap the memory contents to a manual file with the immobiliser disabled, then delete the relevant DTCs from the flash file and tune it at the same time.

I repeat, do not use the instrument cluster (clocks) or other modules from the donor car, it really is just a case of programming the correct ECU for your engine and ensuring that the correct loom, O2 and accelerator pedals are being used.

  • Thank you for your answer. I am going to update the original question with additional details such as the engine codes and ECU codes as well as the DTCs. Looking forward to either a revised answer or additional information based on the extra details provided Commented May 21, 2018 at 3:01
  • I rephrased the question without seeing your answer. Your answer is just perfect! Could you share with me the diagnostic trees or wiring diagrams for the oxygen sensors and wiring? the accelerator pedals and possibly those DTCs. From what you have said, I can easily do 1 and 2 and then get someone else to do 3? Commented May 30, 2018 at 12:46

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