P0031 on 2009-2018 Subaru Forester (Base, Premium, Limited, Touring, XT) — HO2S Heater Control Circuit Low (Bank 1 Sensor 1)
1 vehicles · 1 makes · $150-$450 repair
Most Reported On
P0031 is an OBD-II diagnostic trouble code meaning “HO2S Heater Control Circuit Low (Bank 1 Sensor 1).” The PCM detects low voltage (short to ground or open) in the heater control circuit of the upstream O2 sensor on Bank 1, Sensor 1. This code is most commonly reported on 2009-2018 Subaru Forester (Base, Premium, Limited, Touring, XT), with repair costs ranging from $150 to $450.
Common Causes
Typical Repair Cost
Based on 1 documented vehicle-specific issues. Actual cost depends on root cause and vehicle.
Diagnostic Tools
To diagnose P0031, you'll need an OBD-II scanner. Here are our recommendations at every price point.
ANCEL AD310 Classic OBD-II Scanner
by ANCEL
A simple, affordable code reader that reads and clears check engine codes. Great for quick diagnostics on any OBD-II vehicle (1996+).
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BlueDriver Pro Bluetooth Scanner
by BlueDriver
Bluetooth OBD-II scanner with a free companion app. Provides enhanced diagnostics, smog readiness, and repair reports sourced from a database of verified fixes.
- Enhanced diagnostics (ABS, SRS, transmission)
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LAUNCH CRP123X OBD-II Scanner
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A professional-grade handheld scanner that reads all four major systems (engine, transmission, ABS, SRS) with live data streaming and graphing.
- Engine, transmission, ABS, SRS diagnostics
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Autel MaxiCOM MK808S Diagnostic Tool
by Autel
Shop-level diagnostic tablet with bi-directional control, active tests, and full system coverage. Ideal for serious DIYers and small shops.
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FAQ
What does P0031 mean?
P0031 stands for "HO2S Heater Control Circuit Low (Bank 1 Sensor 1)." The PCM detects low voltage (short to ground or open) in the heater control circuit of the upstream O2 sensor on Bank 1, Sensor 1.
What are the most common causes of P0031?
The most common causes of P0031 are: Open/short in heater wiring, Failed O2 sensor heater, Corroded connector, Blown fuse. The specific cause varies by vehicle.
How much does it cost to fix P0031?
Repair costs for P0031 range from $150 to $450, depending on the vehicle and root cause.
Which vehicles are affected by P0031?
Au7o has documented P0031 across 1 vehicle models from 1 manufacturers: Subaru.
Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.