Powertrain, generic (extended)

P2188 System Too Rich at Idle (Bank 1)

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modeNo

P2188 means the long-term fuel trim of bank 1 has to remove more fuel than allowed in the idle and low-load range, the additive part of the mixture adaptation on Bosch-type systems. GM's 2008 3.6 LLT sets it below -6.0 % at 520 to 1120 rpm and 1.7 to 7.8 g/s, with closed loop and coolant above 60 °C. On the Opel/GM 2.0 turbo in the Saab 9-5 (2010) the weighted long-term trim must stay below its limit for 4 s or 50 s in total (Type B); Saab's test gives -22 to 0 % as normal trim and 19 to 42 kPa manifold pressure at idle. At idle the extra fuel typically comes from sources the ECM does not meter: Mercedes lists for the M132 engine a leaking PCV valve, leaking injectors or excessive fuel pressure, wrong intake pressure readings, a restricted or worn throttle and a contaminated oxygen sensor. A saturated charcoal canister purging at idle has the same effect. Stellantis found an airflow straightener in the air box clipped in wrong, which disturbed the air mass reading and set P2188 and P2190.

Likely causes

Leaking injector or fuel pressure too high
Fuel vapour from the purge valve or oil-diluted crankcase gases
Air mass or manifold pressure reading wrong

Symptoms

  • Malfunction indicator lamp on
  • Rough idle, fuel smell

Repair estimate

DifficultyMediumDIY possible
Parts and labour€20–600
Time0.5–3 h

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

Parts involved

fuel injectorfuel pressure regulatorevap purge valvepcv valvemass air flow sensor

Related codes

P2190P2178P0172P2187

References: gsi.ext.gm.com, saabwisonline.com, static.nhtsa.gov, static.nhtsa.gov.