2009 equinox no sound from the left front door speaker

It comes through the radio an left front 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. The Multifunction Alarm generates the audible warnings on vehicles with RPO UL5 -- Radio Delete Option. The following lists the audible warning priority and the pulse rate:
The radio activates the door ajar audible warning as requested by the body control module (BCM). The BCM sends a class 2 message to the radio indicating the chime frequency of a medium rate and at a continuous duration. The door ajar warning sounds and the door ajar indicator illuminates when the following occurs:

1. The body control module (BCM) determines that the driver's door is open and the signal circuit low. The IPC receives a message via class 2 from the BCM requesting illumination of the door ajar indicator.
2. The vehicle is not in park. The BCM receives a class 2 message from the PCM indicating the gear position.

Class 2 Serial Data Link
The class 2 serial data link allows the following modules to communicate and share data with each other:
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Auxiliary Power Drop Connector

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Body Control Module (BCM)

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Driver Information Center (DIC)

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Electronic Brake Control Module (EBCM)

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Instrument Panel Cluster (IPC)

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Powertrain Control Module (PCM)

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Radio

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Remote Playback Device-CD Player (if equipped with UQ3)

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Inflatable Restraint Sensing and Diagnostic Module (SDM)

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Vehicle Interface Unit (VIU) (if equipped)

The class 2 serial data link allows a scan tool to communicate with the above modules for diagnostic and testing purposes.

The liftgate can be opened by operating the switch on the instrument panel. Battery voltage is supplied to the liftgate actuator through the body control module (BCM). The BCM will pulse the liftgate actuator when a release input is received through the key fob, or the instrument panel switch.
Not sure what your talking about . There is no sensor. there is a relay in the I/P fuse box LIFTGATE PCB relay . an a lift gate actuator motor inside the door . An there is a door ajar switch ,which is part of the latch mechanism. Do you have light lit on the instrument cluster - a picture of a little car with a door open , an maybe a chime sounding ?

Not

Make sure you have connected the remote amp wire. This should be blue/white on the radio and connected to the blue/white on the GMOS-4.

Possibly, the bundle that goes through the door also have speaker wires in them. Check there.

Those are not meant to be plugged into a car, usually its the cord your using. Take it to repair man if nothing helps.

Here you go. Be careful this can disable the truck in some models due to the radio system be tied into the factory anti theft system..

2009 Chevrolet Tahoe Stereo Wiring Diagram
Car Radio Battery Constant 12v+ Wire: Red/White
Car Radio Accessory Switched 12v+ Wire: The radio harness does not provide a switched power source. The accessory turn-on is controlled by the lan serial network. Run a wire to the fuse box or ignition switch harness.
Car Radio Ground Wire: Black
Car Radio Illumination Wire: N/A
Car Stereo Dimmer Wire: The radio harness does not provide a dimmer wire. The dimmer wire is controlled by the lan serial network.
Car Stereo Antenna Trigger Wire: The radio harness does not provide a antenna trigger wire. The antenna trigger wire is controlled by the lan serial network.
Car Stereo Amp Trigger Wire: The radio harness does not provide a amp turn on wire. The amplifier turn on is controlled by the lan serial network.
Car Stereo Amplifier Location: N/A
Car Audio Front Speakers Size: N/A
Car Audio Front Speakers Location: N/A
Left Front Speaker Positive Wire (+): Tan
Left Front Speaker Negative Wire (-): Gray
Right Front Speaker Positive Wire (+): Light Green
Right Front Speaker Negative Wire (-): Dark Green
Car Audio Rear Speakers Size: N/A
Car Audio Rear Speakers Location: N/A
Left Rear Speaker Positive Wire (+): Brown
Left Rear Speaker Negative Wire (-): Yellow
Right Rear Speaker Positive Wire (+): Dark Blue
Right Rear Speaker Negative Wire (-): Light Blue

Front Left Hand LH Driver Side Door Check Stop Linkage
2005 2006 2007 2008 2009 Chevrolet Equinox
Genuine GM Part Number:15861661

I BELIEVE ON THAT MODEL IT HAS A DOOR MODULE THAT CONTROLS THE ITEMS ON THAT DOOR

you need to replace the left front door speaker