P1124moderate severityPowertrain
Long Term Fuel Trim Mixture Too Lean
on 2010 Kia Forte 2.0L I4 · FWD
What this code means
The PCM has detected that the long-term fuel trim is correcting excessively in the rich direction, indicating the engine is running too lean. The fuel system is consistently delivering less fuel than needed.
Symptoms
- Check Engine Light
- Rough idle
- Hesitation on acceleration
- Poor performance
- Possible misfires
Common causes
- Vacuum leak in intake system
- Low fuel pressure (weak pump or clogged filter)
- Dirty or failing MAF sensor
- Exhaust leak before O2 sensor
- Clogged fuel injectors
Diagnostic steps
- Check long-term fuel trim values (excessively positive indicates lean correction)
- Perform smoke test for vacuum leaks
- Check fuel pressure under load
- Clean or test MAF sensor
- Check for exhaust leaks
Repair notes
Repair vacuum leaks or fuel delivery issues causing the lean condition.
Other Powertrain codes on this vehicle
P0001
Fuel Volume Regulator Control Circuit/Open
P0002
Fuel Volume Regulator Control Circuit Range/Performance
P0003
Fuel Volume Regulator Control Circuit Low
P0004
Fuel Volume Regulator Control Circuit High
P0010
Intake Camshaft Position Actuator Circuit/Open Bank 1
P0011
Intake Camshaft Position Timing Over-Advanced Bank 1
P0012
Intake Camshaft Position Timing Over-Retarded Bank 1
P0013
Exhaust Camshaft Position Actuator Circuit/Open Bank 1
P0014
Exhaust Camshaft Position Timing Over-Advanced Bank 1
P0015
Exhaust Camshaft Position Timing Over-Retarded Bank 1