Bank 1 fuel trim is out of the normal correction range (too lean or too rich).
SYMPTOMS
- Check-engine light
- Rough idle
- Hesitation
LIKELY CAUSES
- Vacuum/intake leak
- Dirty or failing MAF
- Fuel pressure issue
- Faulty O2 sensor
- Leaking or clogged injector
DIAGNOSIS STEPS
- Read short- and long-term fuel trims
- Smoke-test the intake
- Verify fuel pressure
- Check MAF and O2 live data
RELATED PARTS
- MAF sensor
- Fuel pump
- Intake gaskets