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When doing 100kph by gps, my speedometer is reading 118kph. I’ve searched these forums far and wide, but the generally accepted solution is “they were designed to read high” and “live with it.” My speedometer is completely useless if it’s reading that inaccurately. My passengers are also discomforted when they think I am speeding, despite the true speed being perfectly legal.

The first solution suggested was to use the digital readout from test 8, but that velocity is only 3kph less than the analog adjusted value, so something is definitely wrong.

Does the 39 use a pwm signal that can be altered with a yellow box, or is it possible to use an aftermarket speed sensor? Wheels are factory and tyres are spec for vehicle too.

I don’t have access to any of the fancy dealership equipment to reprogram the cluster, although I have a second cluster, could I plug this one in for testing without getting a tamper light when I change back the original?

Really appreciate any tips, thanks.
 

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Certifiable BMW Whackjob!
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That error is way bigger than it should be.
You can drive about 120 miles without the cluster and reinstall without getting a tamper dot, but swapping to another cluster...how much different is the mileage in your spare cluster?
 

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Max advance can be as high as +10% of actual plus 4 km/hr. Yours is about 4 km/hr beyond that.

Calibrating the speedometer

is a speedometer DIY possible?

with PA Soft you can recalibrate the speedometer, according to one poster.
 

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2001 BMW E39 540i Automatic Sedan, 200 k miles
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No, a different or wider / higher tire size would throw the speedometer off by 3 to 5 % max. Not the 18% the OP is experiencing.
Note that above 3% in speedometer difference, the ABS can get off kilter. And that may be not safe or even dangerous....
 

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Drive without a cluster completely? Car will not even start (cluster is the link between DME and EWS).
Hmm...really? Is the E38 and E39 different there because I'd swear I read you can do it in an E38, hence where the "approx 120 miles" came from. I suppose I could be mistaken, that thread was at least a couple years ago.
 

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Hmm...really? Is the E38 and E39 different there because I'd swear I read you can do it in an E38, hence where the "approx 120 miles" came from. I suppose I could be mistaken, that thread was at least a couple years ago.
I say you cannot do it in an E38 either. Or even in an Audi A6 C5 for that matter. Best case scenario is a start and then immediate stall.
 

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Asking again...WHAT SIZE TIRES are mounted on the OP's car?

This thread means nothing without this pertinent piece of information? We could drone on & on...but a simple piece of info would rule out the wrong size tires.

The speed signal comes from the left rear wheel speed sensor...see DISTANCE SIGNAL in info below:

Font Rectangle Parallel Number Diagram



And yes, the e38 & e39 share the same communication bus set ups (depending on if you have the high cluster {I-bus} or base cluster set-up {K-bus}).

The 120 miles sounds like the relationship the IKE & LCM have. See datapoint #5 in the info below about REDUNDANT DATA STORAGE.


Product Font Parallel Technology Diagram


Font Schematic Rectangle Parallel Handwriting


Font Automotive lighting Parallel Motor vehicle Art
 
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"Wheels are factory and tyres are spec for vehicle too."

If this is true the problem is elsewhere.
For that much error the tire OD would have to be nearly 4" undersize, I'd think that would be noticeable.
 

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Thanks for pointing out info in the original post that I missed.
Don't feel bad Q, others before you also missed it.
But although OP says they are correct size it still would be nice to get the reply of actual size for verification. Or considering how small they would have be to get such a high error just a picture of the car so we can see the wheels on it.
 
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