Powertrain, generic · Fuel and air metering

P01F6 O2 Sensor Signal Biased/Stuck Lean Bank 1 Sensor 4

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modeNo

Sensor 4 on bank 1 is a fourth oxygen sensor, downstream of a further converter. No manufacturer or vehicle using sensor 4 codes could be identified (GM and Ford documents stop at sensor 3); the description follows CARB's requirements for downstream sensors and GM's checks on sensor 2. P01F6 means the sensor stays lean: the module deliberately enriches the mixture, and if the sensor does not reach the expected rich voltage before a set amount of air has passed, it counts as stuck lean. GM runs this test on sensor 2 once per trip as a two-trip fault. Usual causes are an aged sensor, an exhaust leak ahead of it or a signal wire shorted to ground.

Likely causes

Sensor aged, characteristic shifted lean
Exhaust leak or false air upstream of the sensor
Signal wire shorted to ground or contact resistance
Misfires or mixture fault (excess oxygen)

Symptoms

  • Check engine light on (usually after two drive cycles)
  • Catalyst monitor readiness possibly not set
  • Usually no change in driving

Repair estimate

DifficultyEasyDIY possible
Parts and labour€60–300
Time0.5–1.5 h

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

Parts involved

oxygen sensor bank1 sensor4oxygen sensor wiringcatalytic converter

Related codes

P01F7P01F5P2270P2272P0420

References: law.cornell.edu, gsi.ext.gm.com, en.wikipedia.org.