Chevrolet Repair: 2002 chevy suburban, gm store, chevy suburban

Question
i recently had my check engine light come on on my 2002 half ton suburban. when i read the code it was feul composition sensor to high and to low. the light comes on and off intermittently. also it is hard starting sometimes, does the composition sensor tell the ecm to adjust timing for alcohol in the fuel or what could be causing this problem

Answer
HI SCOTT, YES TO YOUR QUESTION,BUT IT ALSO CHANGES INJECTOR PULSE. WHAT WE HAVE SEEN IS THIS VALVE IS IT DOES NOT SWITCH OVER AS IT SHOULD AND WILL PARTIALLY BLOCK THE FUEL GETTING TO THE INJECTORS, THUS CAUSING ENG NOT TO START OR LONG CRANK OVER. WOULD SUGGEST REPLACING THIS VALVE OF COURSE..I THINK YOU CAN BUY THIS ON LINE FOR A LOT LESS THEN YOUR GM STORE. I BELIEVE THIS SENSOR IS LOCATED BY THE PASS SIDE FRAME RAIL.. I HOPE THIS HELPS YOU AND IF YOU NEED MORE INFO GET BACK TO ME.. TOM....