Powertrain, generic · Fuel and air metering

P0155 O2 Sensor Heater Circuit Bank 2 Sensor 1

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modeNo

The upstream oxygen sensor on bank 2 (sensor 1) has its own electric heater. P0155 is the bank 2 counterpart of P0135: the heater current is outside its window or the driver voltage does not follow the command. GM fails it outside 0.3–3.1 A (8 s or 8 of 10 samples, two trips); Ford outside roughly 0.22–0.465 A minimum to 3 A, with related codes for heater temperature control (P0050) and resistance (P0059). Closed loop on bank 2 then starts late after a cold start, and the sensor checks are suspended. P0135 together with P0155 points to a shared supply or fuse.

Likely causes

Heater element of the sensor burnt out (sensor must be replaced)
Fuse or relay of the heater supply faulty
Heater wiring or connector open, corroded or shorted
Heater driver in the control module faulty

Symptoms

  • Check engine light on
  • Higher emissions and consumption after cold start
  • Follow-up codes P0153/P0154 possible

Repair estimate

DifficultyMediumDIY possible
Parts and labour€5–300
Time0.2–2 h

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

What to check first

  1. Check fuse
  2. Measure heater resistance
  3. Inspect wiring

Parts involved

oxygen sensor heater bank2 sensor1oxygen sensor heater circuitfuses

Related codes

P0135P0050P0059P0161P0153P0154

References: law.cornell.edu, gsi.ext.gm.com, newtonnet.co.uk, saabwisonline.com.