XP: 2002 Fiesta Speedo/Odo EEPROM replacement (long)

Hi all,
I've got problems with the wife's car ('52 1.4 Fiesta Zetec, no ABS). She told me the odo had started displaying all dashes instead of the
mileage. When I checked, it turns out the speedo isn't working either. I guess she doesn't look at the speedo much!
The obvious culprit (confirmed by Google) would be the "vehicle speed sensor" which is a right ba**ard to get to so, rather than take it out, I unplugged it, plugged a new one in and exercised it with a drill whilst looking at the output with a scope. It produced a nice big pulse-train. Unfortunately, the speedo showed no signs of life and the odo still says "------", so I'm fairly sure the original VSS is fine. Bugger.
Putting the dash into test mode gives me two DTCs - E200 and E197. The interweb suggests these are "Invalid odo data" and "Invalid data for speed if tachograph enabled". I'm guessing that the instrument cluster has managed to corrupt some of it's non-volatile storage. From Googling, it seems that Ford dealers change the instrument cluster in these cases. (GBP250 just for the part).
Thinking I'd actually found a legit use for one of those "digi-dash" type places, I phoned one up. They won't touch it for fear of scrambling the PATS immobiliser data.
I took the cluster apart and found an 8 pin EEPROM device inside, which I can easily replace with a blank one. What do you reckon the chances are that doing this will make the cluster look like a new one to the Ford dealer's computer?
The PATS system will make things awkward of course since the car won't start until the dealer has set it up. I'd have to drive the car to the dealer, take out the cluster and bring it home to change the EEPROM. I know this is all a bit desperate, but 250 quid is 250 quid.
Any other ideas? Would an independent Ford specialist be more likely to be able to resurrect the cluster from it's current state?
Cheers,
Colin.
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Colin Stamp wrote:

this thread has an answer that makes sense: faulty abs module which is in between the VSS and the dashboard.
http://www.fordownersclub.com/forums/index.php?showtopic#40
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Mrcheerful wrote:

[snip]
Sadly, there's no ABS on this car.
Cheers,
Colin.
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Colin Stamp wrote:

oops, sorry. the symptoms fit otherwise. have you traced the wiring? It would make sense that the vss leads to the main engine ecu and then out to the dash, is there a signal actually reaching the dash? it goes to pin m18 on the ecu
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Mrcheerful wrote:

I haven't traced it yet because I got really confused yesterday having printed out the wrong circuit diagram. I've checked the signal at the VSS itself, and took out the cluster to check there, but none of the pins had the signals I was expecting and none of the wires were white/blue as the VSS signal is supposed to be. I finally worked out that I had a later cluster and the VSS signal doesn't go there at-all. Presumably the ECU sends speed data via the CAN bus. By the time I'd worked this out, It was too dark to check the signal at the ECU. I'll have to do that tomorrow...
So I guess it could still just be wiring from the VSS to the ECU. Fingers crossed...
Cheers,
Colin.
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