CANbus, replacement car stereos and dodgy steering wheel controls!

One of the side effects of no longer having a company car is that I’m having to take direct responsibility for maintenance again. It’s a world away from my days of learning how to maintain my Mum’s 1980 Ford Fiesta! For example, I recently learned how the wiring in modern cars is totally changed so that it uses a controller area network (CAN) and a serial bus to integrate the various electronic components and to reduce the amount of physical wiring in use. This CANbus system uses common wiring (CAN high and CAN low) and each device communicates using its own frequency… or at least that’s how it was explained to me.

Last month, I had a new car stereo fitted in my family’s 2008 Golf. The Pioneer DEH-4700BT was a bargain at just under £79 (from Halfords) including Bluetooth connectivity to multiple phones for calls and media playback but, by the time fitting and the various cables/adapters/fascia components had been added, the cost had gone up by another £100!

I’m amazed what a difference the new head unit makes on the existing speakers (apparently manufacturers tend to over-specify the speaker to avoid warranty claims if they are “blown” early in the vehicle’s life) but I also learned a little about the car electrics whilst it was being fitted for me.

Initially, the unit was wired in with a live feed taken from the cigarette lighter socket; however that wasn’t needed once all of the necessary parts arrived – the final piece being a stalk control adapter for integration with the steering wheel controls (I can re-use the permanent live if I buy a dash cam in future). Unfortunately, the use of these third party interfaces to the Volkswagen CAN has an interesting side-effect as it seems it listens for control on a range of frequencies, rather than a specific signal. This means that, when I use the steering wheel controls to adjust the car’s multi-function computer (e.g. to switch from fuel economy to distance driven), it skips forward/back a track on the stereo! One workaround is to switch the stereo to Aux input before changing the computer settings, then switching back again – but it is a bit clunky really!

I’ve since found a Mk5 Golf GTI forum post that suggests using Volkwagen’s own single-DIN facia unit and a Connects2 steering wheel interface. It certainly looks like a better finish but having already shelled out over £100, our car (which is certainly no GTI) will keep the AutoLeads version for now (I have an AutoLeads PC99-505 with PC99-SON, which I’m told is the same as the PC99-PIO Pioneer version, a PC2-75-4 harness adapter and an FP-17-03 fascia adapter with removable pocket).

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