Need to replace ECU: will the car start so we can drive it to be reprogrammed?

rosie383

We need to put a 'new' ECU into our VW Polo. We have found one independently for a fraction of the cost of one from VW. Can anyone tell me if the car will be driveable when the new unit is fitted, but only the electrics won't work? I understand that only VW can re-programme it, and TBH, if the ignition would work, then we could drive it rather than tow it to the VW garage.
If anyone knows, I would appreciate it. Thank you.

onejontwo

I doubt it would drive as all the info is stored in the ecu and as it hasn't been programmed then it just wouldn't start. If you're lucky and the donor ecu is from a similar model then it's possible.

Kilty_2

I seriously doubt it'll start and it almost definitely won't drive if it does.

Red_Cat

Is the new ECU a blank one? If so you won't start anything with it. The dealer will have to flash on the right software for your model year, engine type, etc. and may also have to put some injector codes on.

Keep the old ECU, as some manufacturers take an ECM replacement file which means the dealer downloads certain info in a data file from the old ECU and then uploads it to the new one. If this is not available, they have to get the info from the factory. I don't know if VW do this, but the manufacturer I work for (I work with ECU software/hardware) use replacement files.

rosie383

That's very helpful Red Cat. Thanks.