Powertrain, generic · Fuel and air metering

P013B O2 Sensor Slow Response - Lean to Rich Bank 1 Sensor 2

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modeNo

The downstream oxygen sensor (sensor 2, after the catalytic converter) is used for fine mixture trim and to monitor the converter. '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. GM forces the test itself and measures how quickly the signal passes from 350 to 650 mV relative to air flow; a filtered value above its limit sets the code after one trip (fallback: target not reached before about 805 g of air). During this step the control module enriches the mixture slightly. Ford's 2012 petrol strategy tests only the rich-to-lean direction, so this code is documented mainly by GM; Ram also lists it as a soot-related diesel code. 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

Downstream oxygen sensor aged or contaminated (soot, oil, silicone, coolant)
Exhaust leak between manifold/turbo and the sensor
Converter faulty or non-original with different oxygen storage
Control module software too sensitive (update available)
Sensor connector or wiring with contact resistance

Symptoms

  • Check engine light on
  • Usually no noticeable change in driving
  • Catalyst monitor may stay incomplete (inspection readiness missing)
  • With a converter cause, P0420/P0430 may follow

Repair estimate

DifficultyEasyDIY possible
Parts and labour€60–250
Time0.5–1.5 h

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

Parts involved

oxygen sensor bank1 sensor2exhaust systemcatalytic converter

Related codes

P013AP013FP013DP0139P2270P0420

References: law.cornell.edu, gsi.ext.gm.com, gsi.ext.gm.com, static.nhtsa.gov.