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Check the electrical connector at the "IAC" on the cold air intake adjacent to the throttle body. 3 wires, and with key in "run" position, one should be grounded, one should show battery voltage (12 VDC) and the other should show "Reference voltage" (4.6-5.8 VDC)If the wire's values match up, then the IAC itself is probably inop. See if it makes any difference in idle quality if the IAC is unplugged. No difference means IAC is not working. Other than IAC concerns, the one main cause of this concern would be the Torque Convertor Lock-up Solenoid is stuck, which will make the car act the same as a manual transmission would act if it were stopped without pushing in the clutch.
if there's an "x" looking marking over the little light bulb, it's telling you to check for an external light bulb that's not coming on when it should. Parking lights, brake lights, turn-signal lights and back-up lights are all included in this circuit.
If it were just the brake lights not working, I'd replace the brake light switch, down on the brake pedal,with a known good one as the fastest, cheapest diag procedure. But, if the brake lights stopped working at the same time that the turn signals stopped working, and the fuses were all okay, I'd first check the switch that controls the emergency flashers. If the flasher switch is partially engaged or is shorted out, then the battery voltage will not go any farther on that circuit than the flasher. Of course, remember that the light bulbs were each probably installed at the same time, so it's not unusual to discover that they each went bad at the same time, too.
Most probably a vacuum leak between the engine's intake manifold and the heater control head, but could also be caused by a vacuum leak elsewhere on that same vacuum circuit, which includes the vacuum actuator on the front axle and the vacuum reservoir front right engine compartment area. The heat concern is due to either no coolant circulating through the heater core, or the "blend door" not responding to the heater control head because of low/no vacuum supply or, if electrically controlled, the blend door motor is inop. If your Chevy is equipped with electronic climate control, it's most likely the control head, itself
The drive cables have stretched and are no longer engaging the driven gear, usually on the "work" side of the cable. I've had good results by merely shortening the shield part of the drive cables and re-inserting the cable like that. It's always easier to fully remove the seat from the vehicle before starting to disassemble the carriage assembly, but remember to match up the drive assemblies to their individual functions while the seat is still hooked up to vehicles battery.