P1123moderate severityPowertrain
Long Term Fuel Trim Mixture Too Rich
on 2011 Hyundai Tucson 2.0L I4 · AWD
What this code means
The PCM has detected that the long-term fuel trim is correcting excessively in the lean direction, indicating the engine is running too rich. The fuel system is consistently delivering more fuel than needed.
Symptoms
- Check Engine Light
- Poor fuel economy
- Black smoke from exhaust
- Rough idle
- Fouled spark plugs
Common causes
- Leaking fuel injector
- High fuel pressure (faulty regulator)
- Faulty oxygen sensor reading lean incorrectly
- Saturated charcoal canister purging fuel vapor
- Coolant temperature sensor reading cold
Diagnostic steps
- Check long-term fuel trim values on scan tool (excessively negative indicates rich correction)
- Check fuel pressure with gauge
- Inspect spark plugs for rich fouling
- Test O2 sensor operation
- Check for leaking injectors
Repair notes
Correct the root cause of the rich condition, typically a leaking injector or faulty fuel pressure regulator.
Other Powertrain codes on this vehicle
P0001
Fuel Volume Regulator Control Circuit/Open
P0001
Fuel Volume Regulator Control Circuit/Open
P0002
Fuel Volume Regulator Control Circuit Range/Performance
P0002
Fuel Volume Regulator Control Circuit Range/Performance
P0003
Fuel Volume Regulator Control Circuit Low
P0003
Fuel Volume Regulator Control Circuit Low
P0004
Fuel Volume Regulator Control Circuit High
P0004
Fuel Volume Regulator Control Circuit High
P0010
Intake Camshaft Position Actuator Circuit/Open Bank 1
P0010
Intake Camshaft Position Actuator Circuit/Open Bank 1