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Speedometer calibration


knyte
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Installed my McCruise speedo correction 'kit' the other day while doing a multiservice (Rear shock, Throttle body sync, oil change, etc).  But when it came to calibrating it, the instructions say to go into diagnostic mode.  This requires the pressing of the SET and RES buttons together while turning on the ignition.

This is all fine and dandy if you have the McCruise original switches which will allow you to do that BUT I modified my controller to use a stock OEM module which of course only allows for either SET OR RES to be pressed via the rocker switch but not both concurrently!  Oops! never saw that coming when I did the mod.

If you too have done this little mod and find yourself in the same situation in future, there is a workaround that will get you out of the doo-doo with minimal effort required.

I could have rewired my McCruise original switch to a Molex connector and plugged it into the computer end temporarily to set it up then return to normal which would have meant sourcing the plug and pins and putting it together for just this one-time job OR - get creative!

The McCruise uses voltage sensing on a common line to determine SET or RES and likewise for diagnostic mode.  Looking at the control board there are two resistors of different values associated with the SET and RES buttons and they are wired in parallel but are separate from each other in normal use.  These are placed in parallel when both buttons are pressed at once however giving diag mode - but only when turning on the ignition.

For those who may not be aware, when two resistors are in parallel the resulting resistance is a function of the two using a formular which I'll not bore you with but is always less than the smallest resistor.

So, it was simply a matter of unplugging my OEM style controller from the McCruise brain and placing a resistor of the abovementioned determined value (530ohms FWIW) across the common and SET/RES control line, turning the ignition on and Viola! we have diag mode.

Then removed resistor and plugged my OEM control back in to complete configuration of the speedo correction.

Sorry for the long post but someone might get some use out of it if they have a similar setup to me.

 

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On 8/31/2021 at 12:52 PM, betoney said:

Very creative workaround, glad you got it to work. 

...Eventually!

Took it out for a run yesterday as it was the first chance I had since doing the calibration in the garage.   Got about 100M from home and noticed I had TCS and Check Engine lights up.  Also, NO speedo reading at all which probably explains why the alarm lights were up.

Back home and re-read the instructions and it seems that sometimes the power required for the speedo correction CCT is not enabled by default within the McCruise brain.  Thankfully that's all it was. Turned it on via the diag mode, went through the calibration again and now all is good.

I had to do a second recalibration out on the road as it was a little high at 100KM/h (i.e., GPS reading 102 @ 100 on the speedo).  Not much I know but when it can be dialled in precisely, why not!

It's nice to now be confident that what the speedo reads is going to be very close to the real speed.

FWIW mine was out around 8%.

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8 hours ago, dazzler24 said:

...Eventually!

Took it out for a run yesterday as it was the first chance I had since doing the calibration in the garage.   Got about 100M from home and noticed I had TCS and Check Engine lights up.  Also, NO speedo reading at all which probably explains why the alarm lights were up.

Back home and re-read the instructions and it seems that sometimes the power required for the speedo correction CCT is not enabled by default within the McCruise brain.  Thankfully that's all it was. Turned it on via the diag mode, went through the calibration again and now all is good.

I had to do a second recalibration out on the road as it was a little high at 100KM/h (i.e., GPS reading 102 @ 100 on the speedo).  Not much I know but when it can be dialled in precisely, why not!

It's nice to now be confident that what the speedo reads is going to be very close to the real speed.

FWIW mine was out around 8%.

I have the original MCCruise (v1.0 I think) and don't think there are any 'upgrades' or 'add-ons' available for it.  I ride with a GPS 100% of the time and fortunately there is only a 2mph difference in readings, which I am fine with.

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***2015 Candy Red FJ-09***

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16 hours ago, betoney said:

I have the original MCCruise (v1.0 I think) and don't think there are any 'upgrades' or 'add-ons' available for it.  I ride with a GPS 100% of the time and fortunately there is only a 2mph difference in readings, which I am fine with.

I think that I would be happy with that small error as well.

FWIW, this is my label and the two important parts that were required for this to work were: -

MCS7320TBW and Firmware version 5.157+

I was required to send this info to McCruise first so that I was sent the 'right' kit.  They may have other versions that work as well but would require an enquiry from anyone who may be interested.

image.png.2e4263ba2157cebc1d93c29801c6d34c.png

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