A bit of background - my van has a EJ25 conversion which was done by a previous-previous owner. When I bought the van I was told it didn't have a speed sensor fitted, and it came with a still boxed GPS speed sensor. The engine runs well and the only issue is that after ~10 minutes at a constant speed (e.g. motorway / dual carriageway) the revs will drop, but coming off the throttle and back on makes everything normal again. It's a little annoying but all in all not a big deal. The seller of the van was upfront about this when I bought it.
Since getting the van and doing some investigating I've found that there is a speed sensor fitted to the speedo. It's wired up with 12v and earth, and the "VSS" signal is connected into the wiring loom (yellow wire).
At the ECU end there's at least two yellow wires which come out the wiring loom and are connected to the ECU, but I've no idea if these are the speed sensor signal or not. Also at the ECU end are two wires which are not connected to anything, I'm guessing one of these is the neutral position switch, which from what I've read sounds like the right setup. These two wires have a handy sticker which reads "Don't worry about these if van runs funny etc ring me" - no phone number
Using a OBDII reader there's no speed reported by the ECU. So the signal isn't getting picked up.
I don't know who did the conversion / wiring or even exactly which model of Subaru the engine came out of, so that's a bit of an unknown. I've tried looking for a ECU pin out but haven't been able to find one which matches exactly - seems like Subaru had a lot of variations. The ECU is marked "4R / 22611 AH25 / A18-000 D9R / 2508".
Seems like there's a few options:
- The speedo VSS isn't connected to the ECU
- The speedo VSS is connected but is broken
- The speedo VSS is connected and working, but there's some other problem
Does anyone have any knowledge on how the sensors are supposed to work, and does anyone have a good resource for finding / identifying Subaru ECU pin outs?