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VAG Canbus across different generations

CANBus Communications Decoded

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Hi all,I have recently swapped a VAG 1.8T 20V engine with ME7.5 wideband ECU into my 2005 Caddy SDi and whilst it's running spot on there's a CAN fault being picked up by VCDS that are confusing me :? Just for my own education does anyone know if the ME7.5 CAN should talk to the Caddy CAN gateway? The Mk5 based vehicles have a dedicated can gateway module whereas the mk4 based vehicles which the ME7.5 came from used a gateway integrated into the instrument cluster.I have a code saying the gateway can't communcate with the engine ECU and when i scan with vcds i can only talk to the engine via k-line protocol.What's confusing me is that I have cluster functions working such as rev counter and temp gauge which as far as i can tell can only be getting their information from the engine ecu via canbus.

I do have an oscilloscope and the can signal looks good although not as clean when the engine ecu is plugged in.

any thoughts?

Thanks

On the VAG canbus, the ECM sends bits of data for model year, engine model code, fuel type etc.

These data bits not being the info that the gateway is expecting may be part of the source of the DTC stored.

As the gateway handles the comms from the OBD port to the engine via the gateway, the missmatch in data (and possible addressing or handshakes) is causing the comms issue from the OBD.

Its possible that the gateway could be reprogrammed in long coding via VCDS to be looking for the 'right' engine ecu, but this isnt something i could say confidently without extensively researching the topic, but due to the modular almost legobrick design volkswagen implement, it may be possible one way or another.

Thanks for the replay Nathan,

I'll have a dig around in the gateway settings and see if there is anything I can alter. I think in the MK5 Golf R32 it used the ME7.1 ECU which i guess would be a closer match to my ME7.5.

thanks again

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