thats why he's wrong, tell me this then, i had a bad o2 sensor when i drove for about 2 mins my check light would come on, Heat guage still below cold, i could drive 12 hours in 20 degree below weather and my heat guage would still be below cold, and when i pop the hood my engine is just a little bit warm, my radiator is taking in too much cold air, so tell me what one... i already replaced it and it was the o2 sensor but why was it working when my engine wasn't even warm???