An OBD-II vehicle fails an emission test with high CO and HC emissions. Technician A says that the cause may be low fuel pressure. Technician B says the cause may be a restricted return line on the fuel supply system. Who is correct?

B only

b - Technician B is correct because a restricted return line in the fuel supply system could cause a continuous high oxygen (O2) sensor signal, which is from a Rich Exhaust or low oxygen content in the exhaust resulting in high HC and CO. Technician A is wrong because low fuel pressure will not cause HIGH CO (Carbon Monoxide) and HC (Hydrocarbons) emissions, rather it could cause low CO (Carbon Monoxide) and HC (Hydrocarbons) emissions.

Explanation:

answerequity law;