Gmc truck loud door chimes and turn signal and nav/radio buttons...How to fix.

There is no dinger as the other guy suggests . sound comes from the driver door speaker .
The audible warnings alert the driver of a system concern or a critical vehicle condition. The radio generates the audible warnings through the left front speaker. The radio receives audible warning requests via the class 2 serial data line. If the radio receives multiple audible warning requests, the warning with the highest priority sounds first. On vehicles with an audio amplifier, the amplifier instead of the radio generates the audible warnings and receives audible warnings requests via the class 2 serial data line. Either the radio or the audio amplifier is the chime producer. The following lists the audible warning priority and the pulse rate:
Fast rate chime (150 pulses per min)
Medium rate chime (100 pulses per min)
Slow rate chime (50 pulses per min)
Turn signal reminder (will pulse at turn signal flasher rate)

Your best bet ,wear your seatbelt . so the sound goes off . If you do wear the seat belt and the chime sounds ,have a qualified repair shop check it .

The door chime is sent through the stereo system, the chime comes out through the driver side speaker.

Isn't the vehicle under warranty ? Your best bet , take it to the dealer . They will hook up factory scan tool an find the problem . You won't ! You have no idea how complex the electronics are on your vehicle

Hopefully you didn't cut the factory harness

try this
disconnect battery
undo the fuse box and look at the wires behind that fuse you pulled

check that only radio and clock wiring are fitted there

the chime may its own power source

i could be wrong
i thought chime was separate to sound system speakers
and comes from a small but loud sound device on the instrument panel circuit board ..much like a computer

see if the speakers are not blown,,, been there done that.. door chimes work through drivers side door...

Even though it doesn't say locked, it probably is. Check your driver's manual to see how to reset it.

You may have a defective radio or a bad radio harness connection. The door chimes go through the radio.

Good news - they're adjustable. The radio is used to adjust the vehicle's chime level. To change the volume level of the chime, press and hold push-button 6 with the ignition on and the radio power off. The volume level will change from the normal level to loud, and LOUD will appear on the radio display. To change back to the default or normal setting, press and hold push-button 6 again. The volume level will change from the loud level to normal, and NORMAL will appear on the radio display.

Note: Each time the chime volume is changed, three chimes will sound to indicate the new volume selected.

Check the radio fuse. As unusual as it seems, GM has started having the radio (even though not turned on) generate the chimes and turn signal sounds. If the radio fails, all the chimes fail too.

This applies to other vehicles besides the HHR. My 2003 Silverado had the door chimes fade down so I could barely hear them. The fix was to replace the radio (under warranty, fortunately...).