Whenever I apply my left signal turn, my screen flashes on my JVC kw av 60bt deck ,message -check for safety behind with your eyes

Any ideas on what else to check?
Yeah, hook up a professional grade scan tool an check for DTC'S -diagnostic trouble codes in the BCM - body control module. Seeing how it controls (turns on) these lights. Turn/hazard indicators flashing fast means a bad bulb or short circuit somewhere.

DTC B3949: Right Front Turn Signal Circuit
Circuit/System Description
Ground is applied at all times at G200 to the turn signal/multifunction switch. The turn signal lamps may only be activated with the ignition switch in the ON or START position. When the turn signal/multifunction switch is placed in either the TURN RIGHT or TURN LEFT position, ground is applied to the body control module (BCM) through either the right turn or left turn signal switch signal circuit. The BCM then applies a pulsating voltage to the front and rear turn signal lamps through their respective control circuits. When a turn signal request is received by the BCM, a serial data message is sent to the instrument panel cluster (IPC) requesting the respective turn signal indicator be pulsed ON and OFF.

DTC B3951: Right Rear Turn Signal Circuit
DTC B3951 will set when the BCM detects a short to ground or an open/high resistance in the RR turn signal control circuit.

DTC B3950: Left Rear Turn Signal Circuit

DTC B3948: Left Front Turn Signal Circuit

DTC B3445: Stop Lamp Circuit

Turn Signal Lamps
The STOP/TURN/HAZARD fuse in the instrument panel (I/P) fuse block supplies battery positive voltage to the body control module (BCM) for the turn signal lamps. When the turn switch is placed in the LEFT TURN or RIGHT TURN position, ground is applied from G202 through the turn switch, to the turn signal switch signal circuit and to the BCM. The BCM then applies battery positive voltage to front and rear turn signal lamps supply voltage circuits. The left front turn signal lamp is grounded at G100, right front at G101, left rear at G301 and the right rear is at G302.

Turn Signal Reminder
The driver information center (DIC) activates the turn signal warning as requested by either turn signal switch. The turn signal warning sounds when the following occurs:
• The ignition is in RUN.
• The turn signal switch is in either turn position, sensing, within 1 second, an open to battery positive voltage transition in the turn signal control circuit, left or right turn.
• The vehicle has traveled a distance of 1.2 km (0.75 mi) by counting pulses in the rolling odometer class 2 message.
The DIC turns OFF the turn signal reminder when either the ignition switch is turned to the OFF position, or the turn signal switch returns to the OFF position, sensing within 1 second, no transitions from open to battery positive voltage in either of the turn signal control circuits, left turn or right turn.

My first step would be to hook up a factory scan tool an check for DTC'S - diagnostic trouble codes

DTC B3948 Left Front Turn Signal Circuit
Circuit Description
Ground is applied to the turn signal switch. When the turn signal switch is placed in the turn left position, ground is applied to the body control module (BCM) through the left turn signal switch circuit. The BCM then applies a pulsating voltage to the LF and LR turn signal lamps through the LF and LR turn signal voltage supply circuits.

What's the left rear lamp doing ? Flashing fast ?

DTC B3950 Left Rear Turn Signal Circuit

The BCM - body control module controls turn signals . There is no flasher unit . Your best bet would be to take your vehicle to the dealer !
Turn Signal Lamps
The BCM 3, BCM 5, and BCM 6 fuses located in the underhood fuse block supply battery voltage to the body control module (BCM) for turn signal, hazard lamp, and stop lamp operation. Voltage from the BCM 5 fuse used for the front and rear left turn signals, voltage from the BCM 3 for the right front turn signal, while voltage from the BCM 6 fuse is used for the right rear turn signal. When the turn signal switch is place in either the LEFT or RIGHT position, ground from G303 is applied through the turn signal switch signal circuit to the BCM indicating the turn signal request. In response to this signal, the BCM applies a pulsating voltage to the front and rear turn signal lamps supply voltage circuits cycling the lamps ON and OFF. The BCM also sends a message via GMLAN to the instrument panel cluster (IPC) to cycle the turn signal indicator ON and OFF depending on the position of the turn signal switch.

Ignition ON, observe the scan tool Left Turn Signal Switch parameter while using the turn signal/multifunction switch to turn the left turn signal ON and OFF. The reading should change between Active and Inactive.

check that all your bulbs are correct and are making contact. this commonly happens when a wrong bulb is installed in a socket. the other reason this happens is a bad ground, and one bulb uses another as a ground path. I would start at the rear left light and check that everything is good there, then move on to the front. 99 percent of these kinds of problems are at the lights themselves.

It will turn on when I hit the button and the turn signals do work. All of this has led to my ABS lights to come on as well. ??????????? Your best bet , take it to a qualified repair shop or learn to do better explanation's ! Or lean to do automotive electrical testing .
Basic Electricity for Service Techs Ohm law Current Flow Opens Shorts
Electric Testing Techniques You Need to Know

How to Use Multimeter to Troubleshoot Common Problems

Do you know what a wiring diagram is ? How to use a DVOM - digital volt ohm meter ? Free wiring diagrams here http://www.bbbind.com/free_tsb.html Enter vehicle info. year make ,model and engine size. Under system click on lighting ,then under subsystem click on turn signals . Click the search button then the blue links .Check power an ground circuits ! This is how we diagnose electrical faults , not just replacing parts .

Turn Lamps
Voltage is applied through the TURN fuse and the turn/hazard flasher when the ignition switch is in the following positions:
• RUN
• BULB TEST
• START
The voltage travels to the contact in the hazard switch. The hazard switch is located in the turn/hazard-headlamp switch assembly. This contact is normally closed.
When the left turn signal is turned on, voltage is applied to the following components.
• The left turn indicator
• The left front park/turn lamp circuit 14
• The left rear turn lamp circuit 18
The turn lamps turn on immediately. The current flow heats up the timing element. The timing element is located in the turn/hazard flasher. The timing element repeatedly opens and closes the circuit. This action causes the turn lamps to begin flashing.
The voltage that is applied to the left front park/turn lamp is also applied to the left front marker lamp. If the headlamp switch is in the OFF position, the left front marker lamp will find a path to ground through one of the following lamps. The following lamps provide low resistance paths to ground:
• The right front marker lamp
• The right turn indicator
• The right front park/turn lamps
• The left front park/turn lamps
The left front marker lamp flashes with the turn lamps. The voltage drop across the marker lamp is much higher than the voltage drop across the other lamps. The lamps that are used for the ground path will not flash.
When the headlamp switch is in either the PARK or HEAD positions, voltage is applied through the following components:
• The EXT LP fuse
• The marker lamps
• The park lamps
When the left turn signal is turned on, the left marker lamp will have voltage at both connections. The left marker lamp does not light. When the turn/hazard flasher stops the voltage to the turn lamps, the marker lamp is grounded through the turn lamp. The marker lamp does not go on. The left front marker lamp flashes in the following manner:
• The left front marker lamp flashes on when the turn filament of the left front park/turn lamp goes off.
• The left front marker lamp flashes off when the turn filament of the left front park/turn lamp goes on.
Voltage is applied to the right lamps in the same manner, when the right turn signal is turned on.
Hazard Lamps
Voltage is applied at all times through the following components to the normally open contact of the hazard switch in the turn/hazard-headlamp switch assembly:
• The STOP HAZ fuse
• The turn/hazard flasher
When the hazard switch is turned on, voltage is applied to the following components:
• The front turn lamps
• The rear turn lamps
The following lamps flash on and off:
• All of the turn lamps
• Both of the turn indicators
The front marker lamps flash with the hazard lamps on, just as the front marker lamps flash when the turn lamps are on. If the headlamp switch is in the OFF position, the front marker lamps flash on when the hazard lamps are on. The front marker lights will flash on when the hazard lamps are on if the headlamp switch is in one of the following positions:
• PARK
• HEAD
When the hazard lamps are on, the following conditions apply:
• The turn circuit is always open.
• The turn/hazard flasher controls the lamp.
Park/Marker Lamps
Voltage is applied through the EXT LP fuse, to the headlamp switch at all times. Voltage is applied to the park lamps and the marker lamps when the headlamp switch is in the following positions:
• PARK
• HEAD
The front marker lamps are grounded through the turn filament of the respective front park/turn lamp. The front marker lamps light as a result.
Stop Lamps
Voltage is applied through the STOP HAZ fuse to the brake switch at all times. When the brake pedal is depressed, the brake switch closes. This action applies voltage through the turn/hazard-headlamp switch assembly to the following lamps:
• The high mounted stop lamp assembly
• The left tail/stop-turn lamps
• The right tail/stop-turn lamps

the turn signal switch is bad or you have a shrted buld filiment and or socket ground it weak or not making connection

If the fuses are good and the front and rear bulbs are good, change the flasher for the turn signals, even tho the right is working. If that doesn't fix the problem, it might be in the turn sgnal switch on the steering column.
If both bulbs are good for the backup lights and fuses are good, then the backup light switch, which is screwed into the side of the transmission has to bad.

Sounds to me like a bad ground. When the current can't complete through a ground circit it feeds back through the elements ancd can cause all sorts of wierd syptoms.

The fast blink itself can be casued by a burnt out bulb I would check that first.

Then I would check the trailter harness if there is one and unpluch any harness that may be plugged into it. also check each bulb to see if it is seated well. you may be able to see if there is corrorsionaround the bulb terminals at this time is so yo may need to replace the light assembly. Also you could look for any spot where maybe someone in the past tried to tie into the harness to hook up additional lights etc. this may allo moisture in and corroded to the point the wire is "open"

More than likely it is going to be your clock spring behind the steering wheel.

Sounds like a wiring problem . Electric is feeding across from brake light ,probably a bare place in the wiring. Check behind the tailight.