Yes, a vehicle will fail the smog check if it is missing the oil dipstick or has a cracked oil cap. Both, a vehicle's oil dipstick and oil cap, are considered emission components. Crankcase fumes will escape either through the oil level check tube, if the dip stick is missing, or through the oil cap, if the oil cap is cracked, thereby harming the air.
Knobby, off-road tires are frowned upon by smog technicians. They may damage the smog machine's dynamometer due to the excessive vibration they may cause. A smog technician has the right to refuse to smog test a vehicle if they think it may damage their test equipment.
