This is out of GM's Electronic Service Information (ESI)
Turn Signal, Hazard Lamps Circuit Description
Both the TRN-BU and the STOP-HAZ fuses in the IP junction block supplies battery positive voltage to the flasher module, which is part of the hazard switch assembly. When the turn signal switch is placed in either the left or right position, current flow is from the flasher module's left or right hand output to the turn signal switch assembly. The flasher module then sends an on-off (flashing) voltage to either the left turn signals and their instrument cluster indicator, or the right turn signals and their instrument cluster indicator. The front turn signals are grounded at G102. The rear turn signals are grounded at G304.
When the hazard switch is pressed, the hazard switch contacts close and the flasher module is connected to the turn signal lamps. The turn signal/hazard flasher supplies battery positive voltage in an on-off flashing pattern to all the turn signal lamps. All the turn signal lamps and both turn indicators illuminate in the same flashing pattern.
flasher module is #1 in picture below, it is on the brake pedal bracket, below driver side dash .
The service manual says the turn/hazard flasher is mounted above the to the right of the brake pedal mounting support.
It' under the steering column mounted to something metal on the dash. it has a 5 wire connector on it. the 4 way flashers go through that module as well. turn in the 4 ways and listen for the clicking noise to find where it is. it just pulls out of the connector and push the new module inot the connector. It's a pretty easy job.
Flasher is up close to where the steering column mounts to the dash. Does the left signal work? If it does, it isn’t the flasher. Try the hazard lights and get out and look to see if all the lights are working. This way you can tell which is not working, take it apart and check to see if there is power and ground supplied to the bulb. You might have a bulb-socket-wiring problem back to the signal switch in the column.
