Powertrain, generic (extended)

P2273 O2 Sensor Signal Biased/Stuck Rich (Bank 2, Sensor 2)

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modeNo

P2273 means the rear oxygen sensor of bank 2 keeps a high voltage when the exhaust of that bank should be lean. GM's 2016 tables (16OBDG05) check this in fuel cut-off and set the code if the signal is above 100 mV after 9 g of air (Type B); GM's 2024 tables (24OBDG07) compare the lowest voltage during a commanded lean phase with 0.20 V over two trips. The Bosch-based 2005 GM V6 leans the bank after a long high-voltage phase and also fails the sensor above 0.202 V four seconds into a fuel cut. Ford treats bank 2 like bank 1 and uses fuel-cut events from model year 2019. Typical causes are a sensor fouled by oil or coolant on that side or a signal wire touching a supply line. P2099 is the post-catalyst trim of bank 2 at its rich limit; P0158 a voltage above the normal range.

Likely causes

Bank 2 rear oxygen sensor fouled by oil or coolant
Signal wire touching a supply or heater line
Bank 2 front sensor misreading so that the bank actually runs rich

Symptoms

  • Malfunction indicator lamp on
  • Catalyst monitor for bank 2 not completing

Repair estimate

DifficultyMediumDIY possible
Parts and labour€60–350
Time0.3–2 h

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

Parts involved

oxygen sensor downstreamoxygen sensor wiring

Related codes

P2272P2271P2099P0158P013CP2198

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