12v vr6 OBD II Ecu Swap

[steveyj 0]

Hello All,

I have just purchased a second ecu from ebay. Can someone forward advice on how to replace it for the original.

I have had an intermittent fault code since I purchased the car relating to the blue coolant temp sensor. The sensor has been replaced and the wiring seems ok. I'm thinking the ecu is at fault!?

I have VAG COM and understand that a recode is required. However I'm not sure if the car has an inbuilt immobiliser (and keycode transponder) or the third party alarm fitted is covering this feature (and the key is dumb).

Can the original ecu be reinstalled as a fall back whatever happens?

Any advice will be greatly appreciated

Regards,

Steve

[ingham 5]

new ecu should be ok when recoded and old one should be ok for backup ,you may need to take new ecu and car to vw to recode as i have had trouble in recoding immibizer in past and had to take to vw cos my vagcomm couldnt do it.

[Nerih 0]

should be okay, get someone to reset the transponder. since the key is 'dumb' it should be okay just to get it on vagcom.

phone stealth racing, they can help you.

[FishWick 21]

Yep, VW are the only people - currently - that can recode your new ECU to your transponder box. VAG-COM can't do it unfortunately. Ideally, people flogging OBD2 ECUs should include the key, reader coil and transponder box to make our lives easier!

If the Blue temp sender is causing problems, try a 330ohm resistor across the plug and the engine will then think the coolant is at 90 degrees, see if that cures the issue. Cold starting won't be too clever though, so I'd only do it when the engine is hot.

Also the blue plug can sometimes corrode if the plastic splash shield is missing.