Powertrain, generic · Fuel and air metering

P014F O2 Sensor Slow Response - Lean to Rich Bank 2 Sensor 1

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modeNo

The upstream oxygen sensor (sensor 1, before the catalytic converter) is the main control sensor for the air-fuel mixture. 'Slow response' means the signal transition itself is too sluggish – it takes too long to pass between two voltage levels. This code covers the lean-to-rich direction, tested when fuel returns or the control module briefly enriches the mixture. Bank 2 only exists on V and boxer engines. No manufacturer document using exactly this code was found; the description rests on CARB and on the published principle of testing an upstream sensor by periodic mixture modulation, where a sensor time constant above a load-dependent limit counts as a fault. CARB requires separate detection of slow and delayed faults in each direction (phased in from 2009 for downstream and 2011 for upstream sensors).

Likely causes

Upstream oxygen sensor aged or poisoned (silicone, oil, coolant, soot)
Exhaust leak ahead of the sensor (manifold, flange)
Mixture fault: intake air leak, injectors, fuel pressure, air flow sensor
Sensor heater weak, sensor too cold
Connector, wiring or control module software

Symptoms

  • Check engine light on
  • Slightly higher consumption or rough idle possible
  • Higher emissions, possible emissions test failure
  • Often no noticeable symptoms

Repair estimate

DifficultyEasyDIY possible
Parts and labour€80–300
Time0.5–1.5 h

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

Parts involved

oxygen sensor bank2 sensor1exhaust systemoxygen sensor wiring

Related codes

P014EP015DP014DP0153P2A03P0151

References: law.cornell.edu, patents.google.com, newtonnet.co.uk.