Long Term Fuel Trim System Too Lean
2011-2015 Kia Optima 2.4L I4
Description
The PCM has detected that the long-term fuel trim system correction has exceeded the lean limit. The entire fuel system is consistently lean beyond the PCM correction capability.
Symptoms
- Check Engine Light
- Rough idle
- Hesitation
- Poor acceleration
- Possible misfires at idle
Common Causes
- Large vacuum leak
- Failing fuel pump with low pressure
- Clogged fuel filter
- MAF sensor contamination under-reporting airflow
- Intake gasket leak
Diagnostic Steps
- Check system fuel trim values on scan tool
- Perform comprehensive vacuum leak test
- Test fuel pressure at idle and under load
- Clean or replace MAF sensor
- Inspect intake manifold gaskets
Repair Notes
Find and repair the vacuum leak or fuel delivery issue causing the lean system fuel trim.
Related Codes
Other Powertrain Codes
- P0001Fuel Volume Regulator Control Circuit/Open
- P0002Fuel Volume Regulator Control Circuit Range/Performance
- P0003Fuel Volume Regulator Control Circuit Low
- P0004Fuel Volume Regulator Control Circuit High
- P0010Intake Camshaft Position Actuator Circuit/Open Bank 1
- P0011Intake Camshaft Position Timing Over-Advanced Bank 1
- P0012Intake Camshaft Position Timing Over-Retarded Bank 1
- P0013Exhaust Camshaft Position Actuator Circuit/Open Bank 1
- P0014Exhaust Camshaft Position Timing Over-Advanced Bank 1
- P0015Exhaust Camshaft Position Timing Over-Retarded Bank 1
P1128 on Other Vehicles
Common Questions
What does code P1128 mean on a 2011-2015 Kia Optima?
P1128 stands for "Long Term Fuel Trim System Too Lean". The PCM has detected that the long-term fuel trim system correction has exceeded the lean limit. The entire fuel system is consistently lean beyond the PCM correction capability.
What are the symptoms of P1128 on a Kia Optima?
Common symptoms of P1128 include: Check Engine Light, Rough idle, Hesitation, Poor acceleration, Possible misfires at idle.
What causes P1128 on a 2011-2015 Kia Optima?
Common causes of P1128 include: Large vacuum leak, Failing fuel pump with low pressure, Clogged fuel filter, MAF sensor contamination under-reporting airflow, Intake gasket leak.