Correct your speedometer error - no flash or tune required

Spart said:

Hopefully you saw that there are two BT models. The MX is the one that supports MS-CAN (and is more expensive.)

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I ordered:

ScanTool 426101 OBDLink MX Bluetooth OBD Adapter/Diagnostic Scanner

I'm really glad this got bumped into the new posts. What a great write up!

A couple of weeks ago we were doing some radar testing and the Stalker Ka gun was registering 2 mph slower than the speedo in my car. It wasn't enough to get me digging for answers since the error was to my advantage but nice to know anyway.

tal said:

I ordered:

ScanTool 426101 OBDLink MX Bluetooth OBD Adapter/Diagnostic Scanner

Click to expand...

That's the one I have, works pretty great with FORScan.

Is this correct?

I got the error I was supposed to get. However; I've got 4 hex numbers at the end instead of 2.

OK to write?

tal said:

I got the error I was supposed to get. However; I've got 4 hex numbers at the end instead of 2.

OK to write?

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Yes, the last two are a checksum. You let FORScan decide what to put there.

Spart said:

Yes, the last two are a checksum. You let FORScan decide what to put there.

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Thank you!

Programmed & tested OK. Went for a short drive. No CELs.

Will GPS verify tomorrow.

And no 2 honks when exiting the car with the FOB!

Close but no cigar. Speedo indicated is 70MPH and GPS is 69.4MPH.

I'm going to fine tune using these values:

The fine-tuning did it. Speedo on cruise at 70MPH is 70.1MPH verified via GPS.

Saved for later

Tommy V said:

Hey man go on sct website,it tells u right on the website that the sctx4 corrects for tire/gear changes.Im sure this method works too,but u already have an x4.I did mine one week ago.

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You used your X4 to do this on the GT350? I called them and they couldn’t confirm it would until I gave them code from my ECU.

So will the SCT X4 actually work or will I need to go through this as-built method with the adjustment tool?

I'm off by about 2 MPH under actual with my change to 295/35-19 from stock PP.

As I said before the tuning from Steeda on the tire size does not work even though it's stated on their website.

From Matt at Steeda:
That is correct for the S550, changing the tire size causes drivability issues. We are eagerly awaiting on a fix for it as well.

Thank you,
Matt

Matt Henschke
Steeda Autosports Inc
Sales/Tuning Manager
[email protected]
954-960-0774


You must use FORscan for now to correct for speedo errors.

Do you need to change the gear ratio in a V6 manual transmission? Just went from 3.15 to 3.55.

D24112 said:

Do you need to change the gear ratio in a V6 manual transmission? Just went from 3.15 to 3.55.

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Gear ratio is the first four digit block of 726-12-01, see here:

https://docs.google.com/spreadsheets/d/1-gytuV9qPfxvLLcFBIl6nt9h5MGW-NWEPc04cN-ro60/edit#gid=0

Spart said:

Gear ratio is the first four digit block of 726-12-01, see here:

https://docs.google.com/spreadsheets/d/1-gytuV9qPfxvLLcFBIl6nt9h5MGW-NWEPc04cN-ro60/edit#gid=0

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I understand that. My question is more like what happens if I don't change in the BCM?