The Car Care Clinic with the Dr John

90 Chevy Corvette - Short on the Air Bag circuit

Jamie from Acton

Question

Doc! I’m having to deal with a short of some kind that is located on the Air Bag circuit of my ‘90 Chevy Corvette. I have eliminated all air bag connections except the main one from the DERM. If this connection is not made , the car will not run. The car will start and you can drive it about a quarter mile and it will blow the air bag fuse. I think there’s something else on this circuit that is really causing the problem, but I do not have an electrical schematic that details the air bag fuse circuit. Anyway , when the fuse blows, the engine cuts out. I put a new fuse in and it starts up , I go a short distance and it blows another fuse. Hope you can help.

Answer

Jamie the Air Bag fuse on you vehicle just happens to be tied in with the vehicle’s engine computer and a relay or two. After looking at the wiring diagrams for your Vette I could easily see that GM did not intend to make it easy for someone to disable their vehicle’s Air Bag system.

Here's a couple of items you should check for possible causes for fuse failure. The canister purge solenoid and the electric air pump relay; now both units are powered by the Air Bag fuse. A shorted electrical winding in either unit would cause the fuse to blow. The Diagnostic Energy Reserve Module (DERM) is not known for blowing fuses but it is possible. There is an isolation/diagnostic procedure of all the systems that the Air Bag fuse powers, but they should be performed, by a technician that is knowledgeable. Because if you jump the wrong wires, you’ll cause the costly vehicle’s computer to go as Cheek and Chong would say, ' Up in smoke ' Let the professionals look after it Jamie.

Good Luck!
Dr. John