BTR vacuum signal

[Bushbasher]

Where does the BTR 4 spd get it's vacuum signal from? My Fairlane went into limp home mode last night and refused to play. Today I replaced the inhibitor switch hoping that would cure it but no go. The only other time I've had a tranny refuse to change gear was an old tri-matic back in the 80s' and that turned out to be the vacuum line had fallen off of the trans. The BTR doesn't have a vacuum line as such that I can find so I assume it's getting a signal from a sensor but I don't know which one.

Cheers
Bushbasher

[Mr Hardware]

I assume you're referring to the old vacuum hose that ran from the side of a 202 down to the tri-matic that often got blocked or fell off? Yeah nah none of that in a BTR.
If your 4-speed is in limp home mode i'd be focussing my attention on things other than vacuum. Check out causes like low fluid levels (unlikely, you'd more likely get slipping/flaring/banging) or some other condition (over temp, no speedo signal etc).

[Evgeni]

The only sensor that reads vacuum is the MAP sensor - but the computer will make the calculation from a group of sensors.
I'm guessing, tps, crank position for rpm, trans fluid temp sensor, speed transducer and probably MAP. Probably has an allowance for when accessories are on as well.
If your engine is running ok, possibly not a sensor problem.

I recall forscan has some transmission PIDS that you can look at to determine whether the solenoids are getting a signal etc. I haven't really done any homework on it as yet. so can't tell you if they are power or ground side switched, but this would be a way to go to get some direction on fixing this.

[Bushbasher]

Thanks for the replies guys, I just had the gas system ripped our of one Fairlane and fitted to the second car and when I drove it in the car was fine and when I picked it up it was in limp home mode. The problem with that is ; it was late friday afternoon and I didn't realise it was in limp home mode till it was too late and the mechanic had shut and he doesn't work saturdays so I am stuck till tomorrow. There's also a couple of other niggling issues to sort out but the one that made me think vacuum is that it's running rough at idle and running very rich. Above idle it's fine but at idle there's no vacuum going to the back of the converter. I'm now surmising that there's a wiring issue and that the vacuum issue at idle could be related to the trans being in limp mode if where the LPG control box is spliced into the cars loom to pick up the manifold vacuum signal isn't right. Unfortunately that's about where my knowledge and understanding of electronics stops and being slightly colour blind means I can't even go and look at schematics and trace wires to check connections because for the most part I can't tell which wire is which in a bundle.

On top of all this, and what I'm now thinking could be part of the problem, is that although both cars are supposedly identical and built only about 3 weeks apart according to the build dates, apparently there's a couple of the relevant wires in the loom that are different colours from one car to the other according to the fitter so even though he took pictures of everything as he went about removing the setup from the first car it fell over a bit when it came time to refit it to the second car. All this is turning what I was assuming should have been a straight forward swap over into a bit of a headache.


Bushbasher