2012 Impala Speed Limiter question

[jtrosky]

First off - new HPTuners customer here. Don't know enough to tune my car myslef, but am purchasing a pre-made tune from a well-respected tuner (Overkill Motor Sports).

Anyway, I have a 2012 Impala LT with the 3.6L LFX direct-injected engine rated at 300hp and while waiting for my custom tune file, I was reviewing my stock file (from a read all) and I noticed that the speed limiter is reported as 135mph (under both GMLAN and Calibration). However, I know for a fact that the speed limiter is *really* set to 112mph (I've had it show on the DIC when I hit 112mph previously).

Can anyone explain why it's showing at 135mph in the HPTuner software even though it's *really* 112mph??

Just really curious as to where there is a discrepancy...

Thank you!

[jtrosky]

Just wanted to follow-up to my own post in case someone else stumbles upon it while trying to research the same thing.

Apparently, since the speed-limiter it set to "GMLAN" from the factory, it means that the speed limiter is being set by another computer that HPTuners doesn't have access to (such as the BCM) - which is why the 135mph setting under "GMLAN" is not what the limiter is really set to. In my case, the speed limiter was really set to 112mph (again, can't see that value anywhere in HPTuners though), but others with the same model-year car have stated that it was limited to different values (I've heard that the limiter depends on the speed-rating of the tires that came on car from the factory, which makes sense).

So, basically, there is no way to see what the stock limiter is set to - and the only way to modify the limiter is to set the limiter "source" to "Calibration" (instead of GMLAN).

[caesar]

Just wanted to follow-up to my own post in case someone else stumbles upon it while trying to research the same thing.

Apparently, since the speed-limiter it set to "GMLAN" from the factory, it means that the speed limiter is being set by another computer that HPTuners doesn't have access to (such as the BCM) - which is why the 135mph setting under "GMLAN" is not what the limiter is really set to. In my case, the speed limiter was really set to 112mph (again, can't see that value anywhere in HPTuners though), but others with the same model-year car have stated that it was limited to different values (I've heard that the limiter depends on the speed-rating of the tires that came on car from the factory, which makes sense).

So, basically, there is no way to see what the stock limiter is set to - and the only way to modify the limiter is to set the limiter "source" to "Calibration" (instead of GMLAN).

This is done by GM so that the vehicle can be configured with a dealership tool depending on options equipped. Dealers do not have the ability to modify the ECM calibrations. They just set the limiter in the BCM with a simple command depending on which tires you ordered.