Reluctor wheels are attached to both cam gears on the Three-Valve engine. The wheels tell the PCM the position of the cams. Since Two-Valve engines only use one cam-position sensor, all except one tab are cut off of the driver-side reluctor wheel. The single tab will be used to let the computer know the cams’ position. The Two-Valve’s PCM only uses one cam sensor to time the cams against the crank sensor reading at start up.