2009 Fiesta - Aftermarket head unit wiring question

[Sandmann]

Hi all

Apologies if this has been asked before. I have a 2009 Fiesta Zetec and I'm installing an aftermarket head unit (a Kenwood DDX2019DABS) which has wiring for both a speed sensor wire and the parking brake warning light (I have no idea why). Does anyone know where I can conveniently tap into these wires?

Thanks in advance...
Matt

[Sandmann]

Addendum: For any who're interested I recieved a phone call from Kenwood's technical support today and I found out what those connections are for... the Speed Sense wire supports Apple Car Play for navigation when there's no GPS signal available in tunnels etc, and the park brake connector disables the menus when the parking brake's not applied.



Personally I think I'll just be wiring the park brake sensor to the switched +12V supply so it always thinks the brake is on and I can access the menus any time... and unless it's fairly convenient I won't bother with the speed sense since I use an Android phone and I don't give a damn about Apple Car Play.

[73 4V XB]

I think you’ll find the park brake wire can be earthed. When I hooked a DVD unit it had the same thing so you couldn’t watch DVD while driving.

[Luke Plaizier]

I've just been having a chat about the Speed sensor or VSS signal in an earlier Fiesta regarding Cruise Control.

Does your car have Stability Control or ABS? If so, it is unlikely to have a VSS. On ABS/ESC equipped carsm the vehicle speed is obtained from an ABS sensor, and then fed from ABS to PCM (Powertrain Control Module) via the CAN Bus, which then sends the speed over the CAN bus again to the Instrument Cluster. On cars without ABS/ESC, there is a VSS (Vehicle Speed Sensor) usually somewhere on the Gearbox. That VSS line then feeds direct to a pin on the PCM, which interprets it and broadcasts the speed to the Instrument Cluster. Back in the day, the VSS itself would have fed directly to the instrument cluster, meaning you might have found it in the dashboard somewhere.

But if you have ABS/ESC, there's a very real chance you don't have a VSS line anywhere. In the cruise control world, this means they need to be CAN enabled, and either listen for the speed on the CAN bus, or use OBD2 J1979 standard signalling to constantly query the road speed via the CAN bus.

But if you DID have it, it would likely be found between the transmission and the PCM, all within the engine bay.....


Luke