P0174 – System Too Lean (Bank 2)

Description

The ECM detects a lean air-fuel mixture on Bank 2 based on fuel trim and O2 sensor feedback. Use the Fuel Trims guide and OBD2 Live Data guide to interpret the correction before replacing parts.

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Symptoms

Rough idle
Hesitation
Lack of power
Poor fuel economy
Possible misfires

Causes

Vacuum leak on Bank 2 side
Dirty or faulty MAF sensor
Weak fuel pump or clogged filter
Exhaust leak before Bank 2 O2 sensor

Diagnosis

Compare Bank 1 and Bank 2 fuel trims
Smoke-test intake and Bank 2 gaskets
Check MAF data vs RPM
Measure fuel pressure under load

Repair

Repair Bank 2 intake or vacuum leaks
Clean or replace MAF sensor
Correct fuel delivery issues
Repair exhaust leaks before O2 sensor