The Air Bag Light (SRS) or Seat Belt warning light won't go out or the Cruise Control won't engage.

The Airbag officially called the Supplemental Restraint System (SRS) has a controller that illuminates a warning light between the 2 and the 3 in the clock display if it encounters a fault. There are two types of faults, one encountered after a collision that can't be reset. However, most are caused by an electrical issue that can be reset. 

Things that will trip a fault light if done without disconnecting the car battery first include:

• Removing the Steering wheel or its airbag, 
• Unplugging the SRS controller,  
• Removing or replacing the SRS warning bulb in the clock display, 

One will know if their SRS fault is resettable if the warning light extinguishes a couple minutes after the ignition is turned on. 

It can be reset by an onboard diagnostic reader that supports resetting the SRS controller. I use Durametric OBD software with a laptop that has this feature. If you do not have a reader that can reset the controller many independent garages or dealers can in most cases do it for you.

Other faults related to using LEDS in place of incandescent bulbs in a 993:

• Using a LED bulb in place of a filament bulb in the SRS warning light located in the clock display between the 2 & 3 will cause a fault light,
•  Using a LED bulb in place of a filament bulb in the seatbelt warning light located in the clock display between the 9 and 10 o'clock positions will cause a seatbelt fault light unrelated to the SRS system.
• Converting the tail stop lamps AND the high-mounted stop light to LEDs will cause the cruise control to become inoperative. The system looks for a small current through the brake light circuit to ensure the brake lights are operational before allowing the cruise control to activate. If all the stop lamps are LEDs this current does not pass. A workaround is to add a resistor to simulate an incandescent brake light filament to the circuit. 

A general note about warning lights:
The Central Warning Light "!" is always illuminated in conjunction with another warning light, unless the Central Informer Unit is defective, which is rarely the case. Any warning light that has been removed or is blown out will not show up in conjunction with the Central Warning Light. If you have a lit Central Warning Light and no other companion warning light illuminated, turn the ignition from off to on and look and see that all the warning lights illuminate during the initial self-test.

#OBD #OBDC #OBDC-II #On board diagnostic