Astra j speedo error

[Sony96]

Hello everyone,
Is it an easy fix to get the speedo to read the correct speed....on my Astra J OPC if the speedo says 100km the car is only doing 90kmhr
Wife's Astra J GTC auto has a near perfect speedo
Any idea on getting it adjusted, My 1996 Calibra turbo 4x4 also has a near perfect speedo......though a new car would be better lol

[soulman]

check tyre/wheel size and what is stored in ecu as this can affect speedo readout

[domtorredo]

Nearly every speedo has error by couple of mph, they show more than you are actually doing and its normal.

The law for car speedometers in the UK

The*UK law*is based on the*EU standard, with some minor changes.* A speedo must never show less than the actual speed, and must never show more than 110% of actual speed + 6.25mph.* So if your true speed is 40mph, your speedo could legally be reading up to 50.25mph but never less than 40mph.* Or to put it another way, if your speedo is reading 50mph, you won’t be doing more than 50mph but it’s possible you might actually only be travelling at 40mph.


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[Sony96]

check tyre/wheel size and what is stored in ecu as this can affect speedo readout

How do you get this checked or can I get some software to check it

[soulman]

normally this is in the engine ecu.... opcom/vauxcom/tech2 plus there are other things like snapon diagnostics which may be able to do it

[domtorredo]

I think astra mk5 had it in ipc
Mk6 can be in ecu or ipc
But if 1st owner or still original alloys and tyres on than i dont think there will need any changes but if alloys are changed than yes can be out

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[domtorredo]

Use mdi or any other j2534 device as tech2 has only offboard diag for mk6 not sure if opcom/vauxcom will do the job.

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