Powertrain, generic · Fuel and air metering, auxiliary emission controls

P0030 HO2S Heater Control Circuit (Bank 1 Sensor 1)

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modeNo

The upstream oxygen sensor on bank 1 (sensor 1, before the catalytic converter) only delivers a usable signal once its ceramic element is hot. A heating element inside the sensor gets it there quickly after a cold start. Typically the heater receives battery voltage via a fuse or relay, and the engine control module switches the ground side with a pulsed signal while comparing the commanded state with the measured voltage or current. P0030 is the general circuit fault: the measured state does not fit the command, most often because the circuit is interrupted. Which physical fault sets P0030, P0031 or P0032 is defined by each manufacturer. Without heating, closed-loop mixture control starts late and cold-start emissions rise.

Likely causes

Heater circuit interrupted, e.g. broken or chafed wire near the exhaust
Heating element inside the sensor burnt out
Connector corroded or terminal pushed back
Heater supply fuse or relay faulty
Output driver in the engine control module faulty

Symptoms

  • Check engine light on
  • Usually no noticeable drivability problem
  • Closed-loop control starts late after a cold start
  • Emissions test or readiness check failed

Repair estimate

DifficultyMediumDIY possible
Parts and labour€80–350
Time0.5–1.5 h

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

What to check first

  1. Check heater power and control
  2. Measure heater resistance
  3. Inspect wiring

Parts involved

oxygen sensor upstreamoxygen sensor heateroxygen sensor wiringoxygen sensor heater fuse

Related codes

P0031P0032P0036P0050P0053P0135

References: law.cornell.edu, saabwisonline.com, en.wikipedia.org.