85 Celica. all turning signals not working(front and back) brake/tail lights also out. headlights n hazards r good.

The service and repair manual with diagram will provide you step by step help to locate and fix the problem easily and you will get the manual from the given link https://toolsnyou.com/

Check for Power on your License Plate Light, more than likely you have lost GROUND

Turn Signals, Do the Front Work and the Back don't? If NONE then FLASHER FUSE

Yes, it could be switch, check it out, the exhaust is a different story

may have a broken connection in the socket where the bulb goes

I think you have a bad ground at the back on both rear lights or their earth out on the same connection but these american cars use a funny system where the stop lights are the indicators and not a seperate yellow light like europeon motors ,Now these brake light switches also allow the indicators to work by shutting off the feed to the stop light so it flashes with indicators ,Why american cars use this system i dont know as its so complicated for the stop light switch function but try the ground or earth wire on the back lights and if no joy then ask a american mechanic with experiance of this sort of circuitry as when i get american cars for import i have to fit new back lights and disconnect the brake light switch .

Hope this helps your out. I know the diagram and locator is a bit blurry but hopefully it gets what you need.
Drivers kick panel:
Front wiper 20A - Front wiper system Cigar 15A- Cigarette lighter Audio 10A- Audio, remote control mirror Air Bag 10A -Air bag diagnostics Stop lights- 15A -Rear brake light, high mounted stop light ECU B+ 10A - Shift lock actuator, transaxle controle module, radio, engine control module Room 10A - Interior light, clock, ignition key reminder, rear cargo area light switch ABS 10A- Anti lock brake system control unit ECU IG1 10A - Transaxle control module, shift lock actuator, ABS control unit, DRL unit Meter 10A - Instrument panel, back-up switch, electronics time control module, inhibit switch Turn signal 10A- Hazard switch ,front and rear turn lights, turn indicator IGN1 20A - Ignition switch ABS 30A- ABS pump motor TNS 30A- Tail light, license plate light COOL/FAN 30A- Cooling fan Cond/Fan 20A- A/C condenser fan Starter 15A- Start signal , Fuel pump Blower 25A- Blower Motor SR/ACC 10A - Ignition switch Hazard 15A - Hazard and turn signal light D/Lock 25A- Door locks ABS 30A - Anti lock brake system control P/W RH 20A- Power window motor right hand P/W LH 20A- Power window motor left hand IGN2 25A- Ignition Switch
Engine compartment :
Head 25A- headlights IG 2 30A- Ignition switch IG coil 15A -Ignition coil, condenser,generator IC regulator, diagnostic connector. O2 down 10A- Rear O2 sensor O2 up 10A- Front O2 sensor Fuel pump 10A -Fuel pump unit Injector 10A -Fuel injector ,camshaft positioning sensor, purge solenoid valve, EVAP, IAC actuator, Mass Airflow sensor, EGR stepper motor. fuel pump relay coil, vehicle speed sensor. A/Con 10A - A/C compressor controls, cooling fan BTN 30A- Brake light , high mounted stop light. Tail light LH 10A- License plate light, tail light , rear combo light, instrument panel illumination Tail light RH 10A-License plate light, tail light , rear combo light, instrument panel illumination Head low 15A- Headlight Head Hi 15A-Headlight Horn 15A- Horn

Inside kick panel

THE TAIL/MARKER LIGHTS, GO FROM THE HEADLIGHT SWITCH TO THE REAR FOR THE TAIL LIGHTS & TO THE FRONT FOR PARKING OR RUNNING LIGHTS. ALL THOSE LIGHTS ARE ON THE SAME CIRCUIT, { BROWN WIRE } THE BRAKE & TURN SIGNAL WIRES GO FROM THE STOP LIGHT SWITCH & FROM THE TURN SIGNAL/HAZARD SWITCH. NO RELAY IN THE TAIL/PARK CIRCUIT. CHECK THE FUSES WITH A GOOD FUSE TESTER.

Check the grounds on your wiring.
If you have a trailer harness, make sure there are no shorts, or crusty connections

Good Luck chasing the gremlins

Check the tail light failure sensor. Located in the driver's side kick panel fuse box. ~Rick89GTS

one of your bulb is blown one bulb will shut the rest off check all your bulbs.