Fuel & air metering · Diagnostic trouble code

P0174

System too lean (bank 2)

What it means

In plain terms

The bank 2 counterpart to P0171. When both set together the cause is almost always something common to the whole engine rather than one bank.

What sets it

The trigger condition

Long-term fuel trim on bank 2 exceeds the calibrated limit and stays there.

Generic SAE definition. Manufacturers extend and sometimes override these, so the enhanced code on the vehicle in front of you may be narrower than what is written here.

Common causes

5 things that set P0174.

This is the list every other P0174 page will give you. Read it, then read the part underneath it.

What P0174 gives you
  • Unmetered air common to both banks
  • Mass air flow sensor under-reporting
  • Fuel supply: pump, filter, or regulator
  • Intake manifold gasket leak on bank 2
  • PCV system leaking
5 candidates · no ranking · your call
What AceDx gives you
One ranked call
Named specifically enough to order the part, with a confidence number and the evidence printed underneath.
1 call · evidence attached · you can overrule it
A frequency ranking is about every vehicle that ever threw P0174. You are working on one of them.
The actual problem

That list is not a diagnosis. It is a to-do list you did not ask for.

Every one of those 5 causes is now a decision somebody in the bay has to make, under a clock, on a car a customer wants back today.

We haven’t published a verdict for P0174 yet.

We could mock one up. We’re not going to. A fabricated example of our own product’s output is exactly the kind of thing this page is criticizing. Verdicts appear here as the pilot produces them on real vehicles, with the evidence they actually stood on.

Related codes

What often shows up beside it.

All diagnostic trouble codes →

Stop working P0174 from a list.

The pilot runs on your existing scan tool and your live repair orders. Bring us a car that's throwing this code.