HO2S Bank 1 Sensor 1 Control Limit Reached
2006-2006 Kia Optima 2.4L I4
The 2006 Kia Optima is equipped with a 2.4L inline-4 engine. Below you'll find detailed p1166 diagnostic code information including labor time estimates, cost ranges, and technician notes specific to this engine configuration.
Description
The PCM has detected that the fuel control correction based on the Bank 1 upstream O2 sensor has reached its maximum limit. The PCM can no longer adequately compensate for the air-fuel ratio deviation.
Symptoms
- Check Engine Light
- Poor fuel economy
- Rough idle
- Hesitation
- Failed emissions test
Common Causes
- Large vacuum leak
- Faulty upstream O2 sensor
- Exhaust leak before sensor
- Fuel pressure out of range
- MAF sensor malfunction
Diagnostic Steps
- Check fuel trim values on scan tool for direction of correction
- Test for vacuum leaks
- Monitor O2 sensor switching
- Check fuel pressure
- Inspect MAF sensor
Repair Notes
Repair the underlying air-fuel ratio issue causing the control limit to be reached.
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
P1166 on Other Vehicles
Common Questions
What does code P1166 mean on a 2006-2006 Kia Optima?
P1166 stands for "HO2S Bank 1 Sensor 1 Control Limit Reached". The PCM has detected that the fuel control correction based on the Bank 1 upstream O2 sensor has reached its maximum limit. The PCM can no longer adequately compensate for the air-fuel ratio deviation.
What are the symptoms of P1166 on a Kia Optima?
Common symptoms of P1166 include: Check Engine Light, Poor fuel economy, Rough idle, Hesitation, Failed emissions test.
What causes P1166 on a 2006-2006 Kia Optima?
Common causes of P1166 include: Large vacuum leak, Faulty upstream O2 sensor, Exhaust leak before sensor, Fuel pressure out of range, MAF sensor malfunction.
Last updated: March 2026