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Re: speedometer drive ?? Posted by gta [Email] ![]() ![]() In Reply to: Re: speedometer drive ??, Name Left Blank, Tue, 22 Feb 2022 10:35:19 Members do not see ads below this line. - Help Keep This Site Online - Signup |
I'm not quite convinced about the EDU as a problem cause - I assume you mean the unit which shows gas milage etc.
For one thing I've had the EDU fail completely in the past, and replaced it from a spare instrument cluster. It was 5+ years ago but I'm ~98% sure that while it was dead, the speedometer itself still functioned.
The signal from the transmission sensor comes into the speedometer itself on the 2-wire plug, and then a pulse (I don't know if it's the exact same pulse, or regenerated within the speedo) is sent to other systems on the center pin of the 3-wire connector. Can't remember the wiring diagram right now, but the trionic ECU, the EDU and trip computer etc are all downstream of the speedo. Would be interesting to look that up.
There is definitely no speed signal at any of these (even OBD2 shows no road speed). Some have said the drivability takes some time to degrade, others seem to say it doesn't (depending on year?). It only failed on Friday, but I did complete a ~100 mile trip without any problems - still driving okay today.
I *would* like to at least inspect the sender gear (and could also confirm the sender itself by spinning it and looking for signal).
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