Q: Codes showing: P0171, P0420, P0174

asked by on

"We have a minivan and it's showing several codes: P0171 - bank 1-combustion too lean, P0420 - catalyst eff. too low, P0174 - combustion to low What do these things mean. I'm not auto savvy and need to understand before seeing a mechanic."

Hello. These diagnostic trouble codes are an indication that there could be a problem with the oxygen sensor or that there is a vacuum leak. It is possible that the vacuum leak is located in the intake manifold. These codes could also simply be the result of a loose hose. I would suggest that you have a certified technician, like one from YourMechanic, come out and complete an inspection to determine why your check engine light is on.

Was this answer helpful?
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details
  1. Home
  2. Questions
  3. Codes showing: P0171, P0420, P0174

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Fair and transparent pricing

Get a quote

What others are asking

Q: Hole in my radiator hose

Unfortunately, we do not keep handy the pricing information of other service facilities. However, the best way to get a quote for services with Firestone would be to look up a shop near your area and give them a call....

Q: O2 sensor failed

Hi there. A p0420 usually means the catalytic convert is not performing as well as it needs to. Over time, the catalytic converters fill up with carbon and and will not filter out the exhaust gas as efficiently as they...

Q: My truck is giving codes P0171 & P0174

Hi there. If the engine is running lean, then there could be a plugged fuel filter or a faulty fuel pump with loss of pressure. If the pressure is dropping after 20 to 25 minutes, then there could be a...

Related articles

How Do Power Car Windows Increase Passenger Safety?
Power windows are responsible for approximately 2,000 emergency room visits every year. When a power window closes, it exerts enough force to bruise or break bones, crush fingers, or restrict an airway. Though...
How Long Does a Heater Control Valve Last?
Keeping the right amount of coolant in a car is essential in keeping the engine at the right temperature. Failing to have the right amount of coolant or even bad elements...
P0240 OBD-II Trouble Code: Turbocharger Boost Sensor B Circuit Range/Performance
P0240 code definition Turbocharger Boost Sensor B Circuit Range/Performance What the P0240 code means P0240 is an OBD-II generic code triggered when the Engine Control Module (ECM) detects the intake boost...