SERVICE TIPS FOR 'Y' CARS (S.I.R. SYSTEM)

SUBJECT: SERVICE TIPS FOR THE 19 SUPPLEMENTAL INFLATABLE RESTRAINT (SIR) SYSTEM

VEHICLES AFFECTED: 1991 Y CAR

The 1991 Supplemental Inflatable Restraint (SIR) system on the Y car is different from the 1990 system. The following information provides service tips on the 1991 system, and discusses the differences between the 1990 and 1991 systems.

1991 SIR SYSTEM

1. The 1991 'Y' car is similar to the system used on the 'F' and 'B' car. Be sure to use the 1991 Corvette Service Manual to insure proper diagnostic procedures.

2. In the 1991 system, the "INFL REST" light will flash 7 to 9 times after the key has been turned on. In the 1990 system, the light would stay on for 5 seconds after key on, and then go out if no failure had occurred.

3. The "FASTEN SEAT BELT" light will not come on if there is a SIR failure.

4. The SIR system has both current and history codes. If the Diagnostic Energy and Reserve Module (DERM) detects a failure, it will set a current code, and will turn the "INFL REST" light on. If the failure goes away after some period of time, the system will store the code as a history code, and will turn the light off.

5. Current codes may be read by grounding pin K of the ALDL connector, or by using a TECH 1 tool with a 1991 Body Systems cartridge. Current codes will be cleared when the DERM sees that the failure has been corrected. History codes can only be cleared using the TECH 1 tool.

1990 SIR SYSTEM

1. The 1990 system does not have current and history codes. It will store every code as a history code, and will not turn the "INFL REST" light off until the code has been cleared.

2. The 1990 SIR system failure codes can be cleared by grounding and ungrounding pin 'K' of the ALDL connector, as called out in Section 9JA of the Service Manual. Codes can also be cleared using the TECH 1 tool and 1991 Body systems cartridge and adapter.

3. Code 16 (left hand sensor fault) and Code 26 (right hand Sensor fault) may occur due to corrosion on the frame rail. If either of these codes are set, follow the diagnostic procedures in Section 9JA, and the removal and installation procedures in Section 9JB, and clean the corrosion off the front sensors and frame rail mounting locations. The setting of the codes does not affect the normal operation of the system.

General Motors bulletins are intended for use by professional technicians, not a "do-it-yourselfer". They are written to inform those technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions and know-how to do a job properly and safely. If a condition is described, do not assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See a General Motors dealer servicing your brand of General Motors vehicle for information on whether your vehicle may benefit from the information.