When I turn on turn signals (left or right it

Stop Lamps
The brake pedal position sensor is used to sense the action of the driver application of the brake pedal. The body control module (BCM) provides a 5-volt reference voltage and low reference to the brake pedal position sensor. The position sensor provides an analog voltage signal back to the BCM that will increase as the brake pedal is applied. When the brake is applied, the BCM will then apply battery voltage to the left and right stop/turn signal lamp supply voltage circuits and the center high mounted stop lamp (CHMSL) supply voltage circuit illuminating the stop lamps. At the same time the BCM applies battery voltage through the signal circuit to the transmission control module (TCM) and the engine control module (ECM) indicating that the brakes are applied.
Ground for the stop lamps is supplied as follows:
• G402 provides ground for the left rear stop/tail/turn signal lamps
• G403 provides ground for the right rear stop/tail/turn signal lamps
• G301 provides ground for the CHMSL
The stop lamps on this vehicle will not illuminate unless the ignition is in the accessory, run, or crank positions. When the ignition is in the OFF position the stop lamps will not illuminate when the brake pedal is applied.
Battery voltage from the LT TRN/SIG and RT TRN/SIG fuses located in the rear fuse block is also used by the body control module (BCM) for stop lamp operation.

Turn Signal Lamps
Battery voltage supplied to the body control module (BCM) from the fuses listed below is used for turn signal and hazard lamp operation.
• LT TRN/SIG fuse for the left turn signals
• CTSY/RF TRN fuse for the right front turn signal
• RR TRN/SIG fuse for the right rear turn signal
When the turn signal switch is place in either the LEFT or RIGHT position, ground from G300 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. At the same time the BCM sends a GMLAN serial data message to the instrument panel cluster (IPC) to cycle the appropriate turn signal indicator ON and OFF.
Ground for the turn signal lamps is supplied as follows:
• G104 provides ground for the left and right front turn signal lamps
• G402 provides ground for the left rear stop/tail/turn signal lamps
• G403 provides ground for the right rear stop/tail/turn signal lamps

Do you have a factory scan tool (tech2) ? Your best bet , take it to the dealer .

Go to http://www.bbbind.com/free_tsb.html free wiring diagrams ! You having tail light problems ? Do you know how they work ?

They are turned on by the BCM !
Park, Tail, Marker and License Lamps
The park, tail, license, and marker lamps are turned ON when the headlamp switch is placed in either the HEAD or PARK lamp positions, or anytime the automatic light control (ALC) turns the headlamps ON. When the headlamp switch is placed in the park lamp or headlamp positions, ground from G202 is applied through the signal circuit to the BCM indicating the park lamp request. In response to this signal, the BCM applies ground through the park lamp relay control circuit energizing the PARK LP PCB Relay. With the relay energized, battery voltage is applied through the switch side of the relay, both park lamp fuses, and the supply voltage circuits illuminating the park, tail marker, and license lamps. Ground for the left front park and marker lamps is provided at G101 and the right front park and marker lamps at G100. Ground for all rear lamps is provided at G302.
Turn Signal Lamps
The LT T/SIG and RT T/SIG fuses located in the underhood fuse block supplies battery positive voltage to the body control module (BCM) for turn signal and hazard lamp operation. When the turn signal switch is place in either the LEFT or RIGHT position, ground from G202 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.
Ground for the turn signal lamps is supplied as follows:
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G101 provides ground for the left front turn signal lamp

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G100 provides ground for the right front turn signal lamp

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G302 provides ground for the left and right rear turn signal lamps

check the bulbs when you get rapid flash normally 1 pf the bulbs are out

Fast flashing dash signals mean there is a bulb issue-DEFINATELY!

I have gone to two mechanices and no one can fix the brake lights on my 1999 chevy tahoe and i dont know what to do i need help because i have been stoped by the police and its not good HELP ME PLEASE!!!!!!!!!!!!!!

Hello: There are two things that could be dausing this: One is the board that holds the bulbs in the tail light assembly, it could be shorted internally. The other thing is on the rear right fender on the inside there is a electrical distribution box for the rear lights it also could be internally shorted, also the connectors to that box could be corroded and causing your problem. Hope this helps.

I had this problem, and to be honest, it happened to the left side about a week later...it's the board that the bulbs plug into...it's a very common problem with this model. So popular that you can normally get the socket board off the shelf at a parts store! it's extremely simple to replace, and I replaced all the bulbs at the same time!

check fuse number 7 in Engine Compartment Fuse Box , if its ok you need change turn signal switch

There was a recall on this, take to the dealer and they will replace the whole socket on this.