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Home/DTC Codes/Hyundai/Tucson/2016-2021 2.0L I4/P1128
P1128

Long Term Fuel Trim System Too Lean

2016-2021 Hyundai Tucson 2.0L I4

Moderate SeverityPowertrain

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

  1. Check system fuel trim values on scan tool
  2. Perform comprehensive vacuum leak test
  3. Test fuel pressure at idle and under load
  4. Clean or replace MAF sensor
  5. Inspect intake manifold gaskets

Repair Notes

Find and repair the vacuum leak or fuel delivery issue causing the lean system fuel trim.

Related Codes

P0171System Too Lean Bank 1P0174System Too Lean Bank 2P1127ETCS Actuator Power Source CircuitP1127Long Term Fuel Trim System Too Rich Bank 1P1127Long Term Fuel Trim System Too Rich Bank 1P1127Long Term Fuel Trim System Too Rich Bank 1P1127Long Term Fuel Trim System Too Rich Bank 1P1127Long Term Fuel Trim System Too Rich Bank 1P1127ETCS Actuator Power Source CircuitP1127Long Term Fuel Trim System Too RichP1127Long Term Fuel Trim System Too RichP1127Long Term Fuel Trim System Too RichP1127ETCS Actuator Power Source Circuit

Other Powertrain Codes

P1128 on Other Vehicles

Hyundai Accent

1995-1999 1.5L I4

Hyundai Accent

2000-2005 1.6L I4

Hyundai Accent

2006-2011 1.6L I4

Hyundai Accent

2006-2011 1.6L I4

Hyundai Accent

2012-2017 1.6L I4

Hyundai Accent

2012-2017 1.6L I4

Hyundai Accent

2018-2024 1.6L I4

Hyundai Accent

2018-2024 1.6L I4

Common Questions

What does code P1128 mean on a 2016-2021 Hyundai Tucson?

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 Hyundai Tucson?

Common symptoms of P1128 include: Check Engine Light, Rough idle, Hesitation, Poor acceleration, Possible misfires at idle.

What causes P1128 on a 2016-2021 Hyundai Tucson?

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.

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