Pontiac Firebird Turn Signal Problems

Your description makes me suspect that you have front bulbs burned out, loose/corroded connections in the front sockets, or a poor ground connection in the front. Have you looked for things like that?

Sounds like the bulbs burned out. If you mess with the steering wheel disarm the air bag first.

I haven't, but the front bulbs work perfectly when the headlights (and running lights) are on. That leads me to believe that the front bulbs and sockets are not the problem. Also, both sides had the same problem, but not at the same time. This seems to me like a degrading (and now broken) turn signal switch. Does this seem like a logical way of thinking to you?

Since the bulbs are lighting for non-turn situations you are correct in assuming that the sockets and grounds are intact.

Took a look at your machine's wiring diagrams. In my opinion the most likely suspect for your symptoms is the Daytime Running Lamps module. Each front turn signal is supplied first through the turn signal switch and then through the DRL module. If the module is malfunctioning the front turn signals will not flash.

That looks like a likely suspect...thanks for the suggestion!

If that is the case, would the back turn signals fail to cycle?

I think the back turn signals would not flash because with the front bulbs out of the circuit there is not enough current draw through the flasher to make it function normally.

Sure would like to see you do a little more investigation before ordering a new module. Maybe one or more of the inputs to the module is bad or it has a loose connector or something like that.

Here's a description of your turn signal circuit from the service manual:

Turn Signal Lamps Voltage is applied from the TURN B/U fuse 2 to the normally closed pole of the turn/hazard switch assembly (turn signal switch) when the ignition is in the RUN position. The voltage then flows through circuit 141 to the turn signal lamp flasher. Current flow heats the timing element in the turn signal lamp flasher causing the timing element to continuously open and close.

With the turn signal switch in the left turn position, voltage is applied through two circuits. Voltage flows through the left turn signal switch output circuit at terminal H of harness connector C216 and the left rear stop/turn lamp feed circuit at terminal M of C216. Voltage also flows through the left rear stop/turn lamp feed circuit to the left rear turn signal lamp. Voltage flows through the left turn signal switch output circuit to the instrument cluster for the left turn indicator and to the daytime running lamps module. Voltage then flows through the left front turn signal lamp feed circuit to the left front turn signal lamp.

Voltage for the right turn signal lamps flows through the right front turn signal switch output circuit terminal J of C216 and the right rear stop/turn lamp feed circuit terminal N of C216. Operation of the right turn signal lamp is similar to the left turn signal.