Powertrain, generic (extended)

P2189 System Too Lean at Idle (Bank 2)

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modeNo

P2189 is the bank 2 version of P2187: on engines with a front oxygen sensor per bank, the long-term trim of bank 2 has to add more fuel than allowed at idle and low load. GM's 2005 2.8 and 3.6 V6 set it when the additive correction exceeds 7 %, the 2008 3.6 LLT above 6.1 % at 520 to 1120 rpm, airflow of 1.7 to 7.8 g/s, engine load of 11 to 45 % and coolant above 60 °C, and GM's 2024 tables above about 5.5 % over two trips. Because both banks share the throttle, crankcase ventilation and brake booster vacuum, a leak there normally lifts the idle trim on both banks, setting P2187 and P2189 together. A code on bank 2 alone points to something only that bank sees: an intake manifold gasket or runner leak on that side, an injector on that bank, or the bank 2 front sensor or its wiring. Comparing both banks' trims at idle and at 2500 rpm narrows it down.

Likely causes

Intake gasket or runner leak on the bank 2 side
Shared vacuum leak, usually with P2187 present too
Bank 2 front sensor, its wiring or an injector on that bank

Symptoms

  • Malfunction indicator lamp on
  • Rough or hunting idle

Repair estimate

DifficultyMediumDIY possible
Parts and labour€10–500
Time0.5–3 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

intake manifoldintake manifold gasketfuel injectoroxygen sensor upstream

Related codes

P2187P2190P0174P2179

References: gsi.ext.gm.com, gsi.ext.gm.com, gsi.ext.gm.com.