P0174Fuel Trim too Lean (Bank 2)

What it means

The same fault as P0171, on the other side: the computer is adding more and more fuel on bank 2 — the cylinder bank opposite cylinder 1 on a V6 or V8 — and has hit its correction limit. Alone, it points at something specific to bank 2; together with P0171, it points at something both banks share.

Is it safe to drive?

Get it checked soon

Drivable for now, with the same caveats as any lean code: expect rough idle or hesitation to develop, and don't let it ride for months — sustained lean running under load is hard on an engine. If P0171 and P0174 are set together, check the simple shared causes first; it's often one cheap fix.

Common causes

Most likely first.

• With P0171 also set: a shared cause — a dirty MAF, low fuel pressure, or a large vacuum leak
• Alone: an intake-manifold or gasket leak on the bank 2 side
• A cracked vacuum hose routed to that side of the engine
• An exhaust leak near the bank 2 upstream O2 sensor
• Injector trouble on bank 2

What the live data shows

Compare long-term fuel trim across the two banks. Both pegged positive means a shared cause — MAF, fuel supply, a big leak. Bank 2 high on its own while bank 1 sits near 0% localizes it to that bank's intake tract, gaskets, or injectors. As with P0171: trims worst at idle say vacuum leak, worst under load say fuel delivery or MAF.

A scanner that reads all 139 standard sensors shows you these readings live. ScanMyCar charts them as you drive, keeps the freeze-frame stored with the code, and pulls codes from every module — free, with any cheap Bluetooth adapter.

Typical fixes

Cheapest first, where honesty allows.

• Clean the MAF — especially if P0171 is set too
• Smoke-test the intake for leaks on the bank 2 side
• Replace intake gaskets if the leak traces there
• Test fuel pressure under load