spegru
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| posted on 1/12/15 at 04:22 PM |
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Thanks for answering BW
Pin 3 is the input to the ECU from the VSS itself as far as I understand it. I suppose that is where I'm getting a speed reading from on my
Android Torque/Bluetooth OBD combo.
I havn't got a measurement to hand but I can go get one in a little while if I can get my PC/Scope working again
Pin 4 seems to be an output and it does show a nice fat speed related square wave that gets shorter/faster the fast you go.
It's labelled Audio/Cruise/Trip which is an odd combo. I think it's there as a kind of speed broadcast that's picked up by several
items including HID headlamp levelling and Audio that do adjustments related to speed so maybe that's logical. I didnt do very accurate
measurements but my scope trace seems to show an amplitude of 15v (maybe 12 really?) and (roughly) period of ~100ms @~20mph, reducing to ~50 @~30mph.
Amplitude doesn't change
So the ECU is providing a road speed output that goes to various places - but so far not the speedo itself!
See if this pic link works (I've never does photos on this site before)
Scope Screenshots
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big_wasa
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| posted on 1/12/15 at 04:28 PM |
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Vss should be 0~9v
I will have a look and see what else I can find.
I've only done one mondeo dash and that just connected to the vss along with the ecu.
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big_wasa
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| posted on 1/12/15 at 04:57 PM |
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Ok I am coming around to your way of thinking that the vss is also sent by the bus. Looking at the dash wiring I cant see a vss input but you can see
two pins from the dlc. I will be honest I thought the refresh rate would be to low for a real time display.
from dlc to dash
dash pins
13) grey/purple
26)blue/white
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spegru
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| posted on 1/12/15 at 08:21 PM |
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Thanks BW. If you are not certain that the Speed Control unit is involved then it would seem most likely that the speed is sent on the bus with
everything else. But unfortunately on mine it doesn't work even though everything else does (incl Tacho, Temp & Fuel) and that's with
2 different dashes. It seems unlikely (although not impossible) that both are faulty. Then again, the Trip computer is connected directly to Pin 4 .
Why? Maybe the Trip doesn't speak OBD?
Another thought is about the Pin35 white/blue wire that goes from Trip to ECU because blue/white is also the colour of the VSS sensor output.
Coincidence?
So the 4 possible reasons I can imagine for my problem are:
1) Speedo signal is sent on the OBD bus - and I've got 2 faulty dash units
2) Some other unit in the car translates from the Pin 4 VSS trip/audio/headlamp levelling VSS 'broadcast' into another bus-like thing that
I've not connected properly eg speed control
3) There is a VSS pass through from Pin 4 through via another unit somewhere that I've not connected properly.
4) There is something wrong with the VSS even though I can see it clearly on the Pin 4 broadcast. I could just about believe that depending on how the
ECU is constructed internally. I was surprised to see what looked like 15v on my trace.....
What I need is an actual Ford Focus to mess about with!
Maybe I'll also try to get a VSS trace direct from pin 3
steve/spegru
[Edited on 1/12/15 by spegru]
[Edited on 1/12/15 by spegru]
[Edited on 1/12/15 by spegru]
[Edited on 1/12/15 by spegru]
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spegru
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| posted on 1/12/15 at 09:57 PM |
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After a quick trundle around with my PC/Scope I've added some more VSS traces to my flickr page
Scope Shots
The new ones are direct from the VSS (ECU PIN3). I'm not sure what they are supposed to look like
All new ones (Nos 4 -11) taken over about 10 mins - the odd thing is they change shape with the later ones being more square
Do these look healthy?
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spegru
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| posted on 7/12/15 at 04:30 PM |
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Well I've now changed the ECU in case it was faulty.
I knew it was a long shot
Guess what - it didnt make any difference - still no speedo.
So that's 2 ECUs and 2 speedos.
I shall try another speedo as they're fairly cheap on ebay but it's looking more like a wiring problem to be honest
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spegru
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| posted on 8/12/15 at 12:03 PM |
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An update: I just managed to borrow a Mk1 Focus and plugged in a spare dash pod into the obd port via a flying lead to the plug on the back.
The speedometer works - and that's without any wires connected other than power and OBD!
So that's proved 100% that the speedo is connected via OBD
So why the heck doesn't it work in my car when everything else on the dash does? VSS Speed sensor compatibility (this is a Ford Sierra box)? -
but I get a speed reading via my Torque/Bluetooth connection. Just now I even checked it wasn't getting it from GPS
So near and yet so far......
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big_wasa
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| posted on 8/12/15 at 12:45 PM |
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I will have to have a think.
If you think these get the grey material working you should see a Volvo. 
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spegru
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| posted on 8/12/15 at 02:56 PM |
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One other thing I noticed is that the speed reading I get from Torque/OBD Bluetooth is very low. About 15 km/h (that's what it reads in) at what
visually is around 30 mph
Not that surprising I guess as the gearbox sensors are different and likely do different turns per mile. However what that means is that I'll be
needing a speedo corrector of some sort. There are a couple of different types I have heard of. However what that also means is that I'll also
be electronically reconditioning the VSS speedo pulse......
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spegru
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| posted on 11/12/15 at 08:12 PM |
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A bit of a breakthrough:
I noticed that the trip odometer has been changing albeit very slowly such that I wasn't even sure it was changing till this evening.....
So I wondered whether, considering the roughly 50% under reading at present - had I actually been going fast enough for the speedo to register? (local
roads only so far)
So I went a bit faster.....and the Speedo started to work!
So it's a calibration issue. Of course speedos often don't register at very low speeds either. The highest I'd reached was an
(indicated on my Torque app) 15km/h, or around 9.5mph. I got it up to about 20km/h indicated (actually around 40mph) and the dash speedo started to
register
So nothing fundamental then - phew!
So either my Sierra VSS is faulty or it just behaves quite differently different from a Focus one in terms of pulses per mile
What I need to know now is understand the difference between a Sierra VSS and one from a Focus in terms of pulses per mile/km - whatever - and do the
necessary conversion
Does any one know the pulses per mile figures for Focus and Sierra VSS?
[Edited on 11/12/15 by spegru]
[Edited on 11/12/15 by spegru]
[Edited on 11/12/15 by spegru]
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big_wasa
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| posted on 11/12/15 at 08:34 PM |
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They are different between foci depending on gear box. But I don't know by how much.
There must be some one clever enough to do a a budget speed healer.
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spegru
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| posted on 12/12/15 at 11:16 AM |
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Of course 15km/h vs 30mph which is actually an under reading of about 70%!
According to Burton Power, the Type 9 VSS does 8 pulses per revolution (presumably of the gearbox output shaft).
My info (from the passion ford people) is that the focus VSS does 40 pulses per wheel revolution.
I'm guessing I need to multiply the pulses per gearbox revolution by the Diff ratio to get the per wheel rev figure. Not sure what my diff ratio
is to be honest but assuming it's about 3.6 that would take the figure to ~28.8
So that would provide an inaccuracy of 28.8/40= 72% - which is about what I've seen!
I need a speedo healer.....
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DW100
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| posted on 12/12/15 at 04:15 PM |
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8 pulses per revolution will be of the speedo sensor. There is gearing from the gearbox output shaft to the speedo drive that you have to allow for.
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spegru
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| posted on 18/12/15 at 08:17 AM |
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Thanks DW. I bet you are correct about that. I don't really know what the pulse per rev figure for the built in vss is it might be different so
I'm getting an external one just to try, but I suspect it will be the same. I have also discovered that there are different worm drives for the
gbox but I bet that won't be enough for my purpose where I need to speed up the thing by more than double. There could be an electronic speedo
healer fix for that although those are pretty expensive........
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snowy2
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| posted on 11/4/16 at 08:36 PM |
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installation is almost complete on my Focus engine project....
i will produce some wiring diagrams to aid those who follow me.
i have a set of wiring pin outs for the 60 pin ECU, and all the PATS and OBD connections, now its all been stripped down i can see how easy it would
have been to install. it turns out that the engine electrics on the focus are very easy to adapt, the 16 pin connection to the fuse box just needs
cutting away and of them only 11 pins are used. the under dash connector needs keeping but the wires will be cut off.
i will give a full colour code wiring and pin out.
HOWEVER.......not being as fully upto date with ECU wiring as i could be, a question...
will the ECU need to see 2 Lambda sensors or will just one do?
The Focus OBD plug has a "K" line but i dont know where it was connected to (it went to the plug box where the alarm module pluged
in).....if it was connected at all. all the other OBD connections are straight forward and are made. but what do i do with the "K" line?
(pin 7 on the OBD plug.)
[Edited on 11/4/16 by snowy2]
sometimes you are the pigeon, most of the time the statue.
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spegru
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| posted on 12/4/16 at 06:27 PM |
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I've only got one lambda and no Cat on mine. Seems to run fine but may be heavy on fuel (not sure as my speedo is still way out and fuel guage
may not be working properly either)
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snowy2
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| posted on 12/4/16 at 08:50 PM |
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This is what I have so far... I will do a more comprehensive description later
..Dave. ..
sometimes you are the pigeon, most of the time the statue.
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big_wasa
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| posted on 13/4/16 at 07:39 AM |
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The k line is a bi directional communication that is used to talk to other moduals. Out of the donor there are no other moduals so I have removed the
pin from the plug.
With two O2 sensors the first is used for fuelling when in closed loop. Ie mid throttle once fully warmed up. The second is to report to the ecu on
the function of the Catalytic converter. It will give codes with out it.
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snowy2
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| posted on 13/4/16 at 08:47 AM |
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My suspicion was right the first lambda is needed the second is redundant if no cat fitted.....I can live with some fault codes :-)
I thought the k line was body module related.....good to see my guess was right.
again not needed.
[Edited on 13/4/16 by snowy2]
sometimes you are the pigeon, most of the time the statue.
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snowy2
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| posted on 25/4/16 at 07:23 AM |
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My Focus ecu has an extra wire not listed by the 60 pin diagram listed before....all of the other wires were the same colours. it went to the BCM
(body control module) under the dash. it had the same colour as the VSS wire. i assumed that it was the speed signal for the dash....dont know if it
helps you.
sometimes you are the pigeon, most of the time the statue.
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big_wasa
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| posted on 25/4/16 at 07:49 AM |
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Could be a speed signal for cruse control or traction control ?
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snowy2
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| posted on 26/4/16 at 06:57 AM |
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thats a real possibility. my car had the inlet manifold removed complete because it had cruise control with it before i bought it from the breakers.
sometimes you are the pigeon, most of the time the statue.
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classictinker
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| posted on 6/5/16 at 08:16 PM |
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Would the info in this thread apply to the focus St170? I'm guessing the answer is no as nobody has mentioned it lol.
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AndyW
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| posted on 6/5/16 at 08:23 PM |
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quote:
Originally posted by classictinker
Would the info in this thread apply to the focus St170? I'm guessing the answer is no as nobody has mentioned it lol.
Check out the ST170 how to thread
Click me....
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big_wasa
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| posted on 6/5/16 at 08:24 PM |
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You mean like this thread 
http://www.locostbuilders.co.uk/viewthread.php?tid=190440
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