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Discussion Starter · #1 ·
I'm driving a Mazda 3 from 2016. Just after the warranty period was up the GPS started becoming unreliable - getting lost, can't find satellites, etc. Eventually resets, but often gets lost at the worst time. I've updated the firmware, updated maps, and replaced the GPS antenna. Still problems, although sometimes it works fine on a single trip.

Beginning to think it's some software issue with Bluetooth and/or phone that locks out the satellite connection randomly. Any ideas?
 

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There is a TSB around about that issue, unfortunately I don't think dealer would honor it now, you could try.
If I remember correctly is something caused by inadequate CMU shielding between Bluetooh, GPS and wifi modules. Google it. Make sure you're running the latest firmware, request via PM to @ASH8
 

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Discussion Starter · #3 ·
Thanks. I may have solved the problem. I did notice that the GPS satellite signal capture was affected by Bluetooth activation, power windows, A/C leading me to suspect there was an electrical problem somewhere. Sure enough the diagnostic panel showed
DTC B1238:16 [CONNECTIVITY MASTER UNIT]
Description
Tuner and amp unit (TAU) low power supply voltage input​
Detection condition
  • Connectivity master unit (CMU) detects power supply circuit voltage for tuner and amp unit (TAU) of less than 10 V for 10 s or more with the ignition switched ON (engine off or on).

So I checked related fuses and disconnected/reconnected the main circuits to the fuse box from the battery. Suddenly the GPS reception is back to normal so I suspect that a connector had become loose or could be bad. I no longer get the error code either. I'm keeping my fingers crossed.
 
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