DTC Atlas
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Atlas / DTC Atlas / P0171
P0171Powertrain
Powertrain · SAE
System Too Lean (Bank 1)

Meaning

The ECU detects too much air relative to fuel (a lean mixture) on bank 1, beyond what fuel trim can correct.

Common causes

  • Intake air or vacuum leak (manifold, vacuum hoses, gaskets)
  • Dirty or inaccurate mass-air-flow (MAF) sensor
  • Low fuel pressure, weak pump or clogged fuel filter
  • Clogged injectors
  • Exhaust leak near the upstream oxygen sensor

Symptoms

  • Check-engine light
  • Rough idle and hesitation
  • Possible misfire
  • Reduced power

Severity

Moderate: if ignored it can lead to misfires and engine damage over time.

What to do

  1. Smoke-test the intake for air leaks
  2. Clean or check the MAF sensor
  3. Verify fuel pressure and the injectors

Format conversion

SAEP0171
HEX0171
VAG00369
Open in the DTC converter →
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