This can happens for three reasons only – either the balance has been adjusted to one side .. or most commonly we find that the unit has been replaced previously and hasn’t been coded – this triggers ‘component protection’ and will allow the unit to function from one channel only. The best way to test this is to diagnostically scan the car and check the ‘ amplifier module ‘ section – it will probably report ‘coding error’ . To rectify this you will need to use ODIS or VAS to ‘pair’ the unit back to the vehicle. VCDS or ROSSTECH is not able to remove component protection.
Occasionally ( around 5% of repairs ) a badly water damaged or processor damaged unit may have corrupt data after repair , or , have corrupt or lost data in the gateway module of the car . When the unit is originally operating there is also data ( not just audio ) being transmitted and received by the mmi system , any ongoing interruption to this data will cause the data stream to be inconsistent and potentially cause a ‘ miss match ‘ in the stored data between both the amp and the car – this will trigger a coding issue.
Due to it being encrypted data , the only solution is to recode the unit.
Also previous attempts at repair may also lead to VIN data being lost or corrupted.
If someone has tried to ‘ code ‘ another unit to the car – the previous coding details are erased – hence the original correct unit will then need ‘ paired ‘.
Another common issue which we come across is … customer takes the car to a garage – garage try to reset or ‘ reboot ‘ the amplifier using VCDS or hand held diagnostic equipment – very often they erase or corrupt the coding detail … unit comes to us for repair .. on return the MMI system now requires coding – this is ONLY because the garage has affected the coding .
To test if the amplifier is functioning on the drivers side , try the handsfree or the navigation voice assist – it’ll come from the drivers side of the vehicle.
An example VCDS Log is here –