Why do I get a p0401 code on my engine?
Why do I get a p0401 code on my engine? Some manufacturers use the oxygen sensor to monitor the oxygen (air fuel) ratio in the exhaust as the engine is running. The computer will watch the o2 sensor signal as it commands the EGR valve open. If it does not see the right change in the o2 sensor signal, it will flag your P0401 code. What does code p0299 mean on Duramax Diesel? On the GM Duramax diesel, this code may mean the turbo housing resonator has failed. If you have a Ford, you'll want to next check the wastegate...