Holden Speedo calibration

[rally1]

How do I go about changing the Speedo calibration for a 2007 Holden VE E38 auto?

I used the Speedo fine tune calculator (it was 7% out) and applied it but it made no deference to the instrument cluster displayed speed, what am I missing this cant be hard as im sure there are a lot of diff changes carried out on these.

Thanks.

[Taz]

You have to change values in both the ECM and TCM. I take it you changed tire size or gear ratio or both ? The speedometer calculator is often active in both the ECM and TCM tune files, generally using the it in the TCM tune file will effect changes to displayed speed.

If you want, post the changes to the vehicle, including tire size & manufacturer, and your ECM & TCM tunes (unmodified) and I'll take a look to see if there is a readily apparent fix.

Regards,
Taz

[rally1]

Sorry I forgot to mention that I did program the TCM with not change in speedometer.

I think that Holden uses the ABS module for the instrument cluster speed as we just unplugged the ABS and had no speedometer, If that’s the case has anyone had experience with using a Tech2 for recalibrating the speedometer in the Holden ABS module?

Or do we need to program police mod into the instrument to enable speedometer calibration in the IPC? Thanks.

[Taz]

OK … Gen IVs are not my area of expertise, but I believe the communications route (CAN) is ECM then TCM then ABS then BCM. Also believe communication then branches off from the BCM to the DLC and IPC. At least on North American models, not sure about Holden.

On a North American model, unplugging the ABS would “end” the chain of communication at that point – and nothing would get to the IPC – therefore no speedometer.

You will need to confirm the Holden CAN route, but the speedometer issue may still be in the ECM / TCM.


Regards,
Taz

[gmh308]

The GMLAN does daisy chain in and out from the ECM to the DLC via TCM and ABS/EBCM. Surprising the engine even started with the ABS/EBCM unplugged given the ECM wont start the car unless the BCM tells it to. Plus the instrument panel does not like to be missing the ABS/EBCM. Bing! :)

The VSS does come from the wheel speed sensors in VE/G8/Camaro. But it is processed in the ECM and then sent to the instrument panel via the GMLAN through the BCM ("Gateway") then on low speed CAN to the instrument panel. GM changes only the ECM for different wheel sizes. Oddly they dont touch the trans. i.e. the trans calibration is the same for all wheel sizes.

[rally1]

Yer we just worked out that we took the bus down and thats why there was no speedo (we had to start it them remove ABS), do you now what to adjsut to fine tune speed? do we change the wheel size only?

[Taz]

Please post your ECM & TCM tunes ... will take a look and try to confirm required changes ...


Regards,
Taz

[gmh308]

The only parameter showing as changed in EFILive is the wheel circumference between platforms with different wheel sizes. Though there may be more sitting there in the speedo segment related to the newer way GM is managing VSS/Speedo. :)

Edit: Just checked the speedo segment and the only thing GM is changing in there is the tyre circumference. Nothing else is changed. :)

Would suggest you put everything else back to stock in ECM and TCM and try the circumference change by itself.

[rally1]

Thanks gmh308,

changed H0139 & H0140 wheel rolling circumference and that fixed the calibration. I really thought H0101 Vehicle spped pulses per Kilometer and H0105 ECM pulses per kilometer output rate, would have been prime candidates but they made no difference.

[gmh308]

Cool bananas. Solved! :)

Cheers, Ian