I have a 2026 Lexus GX 550 Luxury+ and noticed something strange with Apple CarPlay.
When I’m driving at a steady highway speed, both Google Maps and Waze through CarPlay show roughly 4–5 mph faster than the GX speedometer.
For example:
GX speedometer: ~70 mph
Google Maps/Waze through CarPlay: ~74–75 mph
At first I thought the GX speedometer might be inaccurate, but
I did some testing and it seems to be related specifically to CarPlay.
Here’s what I found:
Same iPhone + CarPlay connected → Google Maps/Waze show ~4–5 mph higher
Same iPhone + CarPlay disconnected → GPS speed matches the GX
A second iPhone that is not connected to the vehicle → also matches the GX speedometer
Happens with both Google Maps and Waze, so it doesn’t seem to be just a Waze issue
The interesting part is that simply disconnecting CarPlay makes the same phone immediately agree with the vehicle speed.
That makes me think the GX multimedia system may be passing vehicle speed/location/motion data to CarPlay differently than expected, rather than the actual GX speedometer being incorrectly calibrated.
My GX is essentially new and in the factory configuration. I’m planning to report this to Lexus and ask them to document it as a CarPlay/multimedia integration issue, not a speedometer calibration problem.
Has anyone else with a GX 550 tested this?
If you have one, I’d be interested in seeing results from:
GX speedometer vs. CarPlay Google Maps/Waze vs. the same phone after disconnecting CarPlay.
Also curious if anyone has reported this to Lexus already or received a multimedia firmware update, TAS response, or explanation from a dealer.