Chevy Service Manuals Original Shop Books - Factory Repair Original Chevrolet Repair Manuals.ten by General Motors specifically for the year and vehicle(s) listed. Official Shop Manuals that the dealers and shop technicians use to diagnose, service and repair your Chevy Pick-Up Truck, Astro Van, Blazer, Camaro, Colorado, Corvette, Cruze, Equinox, Express Van, S10, Silverado, Suburban, Tahoe, or Volt vehicles. O2 Sensor Eliminator MAGNUM EZ CEL FIX Oxygen Sensor Simulator In general: the downstream but upstream has to work flawless in full range. If you intend to buy a simulator hence decatting, header or modified exhaust, the downstream sensor has to be fooled by all means. See position diagram . Headers or precat gutting requires upstream simulator as well. Questions and answers