P0037
PowertrainHO2S Heater Control Circuit Low (Bank 1 Sensor 2)
The bank 1 sensor 2 (rear) oxygen sensor heater control circuit is reading low. Either the heater element has shorted internally or the wiring has shorted to ground, in either case the ECU sees more current than expected.
ⓘ Information only. This page provides general educational information about fault code P0037. We do not assess the urgency or safety implications of any specific fault. That requires in-person diagnosis by a qualified mechanic. Full terms.
Recommended next steps
Whether a fault is urgent, drivable, or routine depends entirely on the cause on a specific vehicle, and that can only be determined by a qualified mechanic with diagnostic equipment. If a warning light is illuminated, the most reliable next step is professional diagnosis.
What does P0037 mean?
P0037 is a Powertrain (engine, transmission, fuel system) fault code. It indicates: HO2S Heater Control Circuit Low (Bank 1 Sensor 2).
This is a standardised OBD-II code. The technical definition is the same regardless of the make or model of vehicle, although specific causes and symptoms can vary between vehicles.
Symptoms commonly associated with this code
Symptoms that drivers often report alongside this code. Not all may apply to every case:
- • Engine warning light
- • Slightly worse fuel economy on short trips
- • Drivability typically unaffected
- • Sometimes returns intermittently with seasonal temperature changes
Possible causes
Causes commonly associated with P0037, listed in approximate order of typical investigation. The actual cause on a specific vehicle can only be confirmed by professional diagnosis.
- 1. Heater element internally shorted, age-related failure
- 2. Wiring shorted to ground, often where the loom rubs against the exhaust shielding
- 3. Connector contaminated, conductive grime or moisture bridging the pins
- 4. Faulty sensor drawing excessive heater current
- 5. Damaged loom from a previous repair (lifted exhaust gaskets, dropped brackets)
How mechanics typically diagnose
A typical diagnostic sequence used by mechanics, provided here for educational reference only. Diagnostic work should be performed by a qualified mechanic with the appropriate tools and training.
- 1. Test heater resistance, healthy is 5-15 ohms, significantly lower confirms internal short
- 2. Inspect wiring back to the ECU for chafing
- 3. Check connector for water and corrosion, the rear sensor sees more weather than the front
- 4. Verify supply voltage and ground integrity
- 5. Disconnect-and-test, with the sensor unplugged, does the code clear? If yes, the sensor is the fault
Common questions about P0037
Difference between P0037 and P0141? +
Different angles on the same sensor's heater. P0037 is the heater control circuit reading low (electrical fault). P0141 is the heater performance code (heater drawing wrong current overall). Both result in the same diagnostic: test the heater, replace if internally shorted or open.
Will my MOT pass with P0037? +
Code itself doesn't fail MOT, but engine warning light on at MOT time fails automatically post-2018. Fix and clear the light first.
Could a recent exhaust replacement have caused this? +
Possibly. After exhaust work, sensors are sometimes refitted with damaged threads or cross-threaded, putting strain on the connector. The wiring may also have been disturbed and chafing started. If P0037 appeared shortly after exhaust work, that's the first place to look.
Information only, not professional advice
The information on this page is provided for general guidance and educational purposes only. It is not a substitute for diagnosis or repair advice from a qualified mechanic. Always verify any fault before paying for repairs. carfaultcodes.co.uk accepts no liability for decisions made based on this information. Full terms →