Speedo Calibration

[Mark Barber]

I've changed wheel size and now my VSS when logging is spot on checked against a GPS ( before it used to read low ) but my speedo is now reading 4% fast, can I change my speedo without changing the logged VSS. I'm thinking changing H0105 or H0106 may have the desired result but I'm not sure.

Thanks, Mark

[Ira]

I've seen some very non linear speedometers when driving them on the bench using an accurate signal generator. Some are perfect from 20 to 80 and others are on at 80 and 15% high at 30. If the logged number matches a GPS exactly and the needle is off, move the needle.

Pull the dash. I like pulling the kick panel and lowering the steering column as far as I can without removing the nuts, but it can be done without that. Remove the clear cover and replace the dash. turn on the ignition and using a piece of tap mark the static position of the speedo. Now pull the needle and move it slightly and go for a ride. When you're happy, take off the tape and put the cover back on. If you always put the needle back on with the ignition on the tape will let you know how far you've moved the needle.

Ira

[GMPX]

Mark,

Assuming you are driving a Commodore given you are from NSW, we have the problem of Holden 'adjusting' each dash to suit the tyre/wheel combo fitted to the car from new.
So although you have now got the PCM corrected the dash is not calibrated correctly, TechII can adjust the dash PPK, without a TechII try messing with H0105.

Cheers,
Ross

[Tordne]

Mark,

Assuming you are driving a Commodore given you are from NSW, we have the problem of Holden 'adjusting' each dash to suit the tyre/wheel combo fitted to the car from new.
So although you have now got the PCM corrected the dash is not calibrated correctly, TechII can adjust the dash PPK, without a TechII try messing with H0105.

Cheers,
Ross

Is this on all models/series of Commodores? The H0105 parameters doesn't seem to get updated when changing tire or diff ratios.

I have a 3.91 diff ration with 245x35 R19 wheels/tires. Would you know what these values should be?

Cheers,

[Mark Barber]

I changed H0105 by -20% to see what effect it would have, the speedo then read low while the logged VSS didn't change so it had the desired effect I then changed my original H0105 figure by -4% and the speedo and logged VSS are now spot on This is on a VX commodore for anyone who's interested