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

P0037 HO2S Heater Control Circuit Low (Bank 1 Sensor 2)

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modeNo

The heated oxygen sensor on bank 1 is the downstream sensor 2 behind the (first) catalytic converter, used mainly to monitor the converter. Its heating element brings it quickly to operating temperature. Typically the heater receives battery voltage via a fuse, and the engine control module switches the ground side with a pulsed signal while checking that the circuit state matches the command. P0037 means the control module measures too low a voltage or current in the heater control circuit, for example because of a short to ground or, depending on the system, a burnt-out element. Which physical fault sets the general, low or high code is defined by each manufacturer. Without heating, the sensor becomes ready late and catalyst monitoring may not complete.

Likely causes

Control wire shorted to ground, or heating element burnt out (system-dependent)
Supply interrupted or fuse blown
Corroded connector with high contact resistance
Output driver or software of the engine control module

Symptoms

  • Check engine light on
  • Usually no noticeable drivability problem
  • Catalyst monitor does not complete
  • Emissions test or readiness check failed

Repair estimate

DifficultyMediumDIY possible
Parts and labour€80–350
Time0.3–1.5 h

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

Parts involved

oxygen sensor downstreamoxygen sensor heateroxygen sensor wiringoxygen sensor heater fuse

Related codes

P0036P0038P0057P0054P0141

References: law.cornell.edu, saabwisonline.com, saabwisonline.com, static.nhtsa.gov.