P0138: O2 Sensor Circuit High Voltage (Bank 1, Sensor 2)
3 vehicles · 1 makes · $150-$1,400 repair
Most Reported On
P0138 is an OBD-II diagnostic trouble code meaning “O2 Sensor Circuit High Voltage (Bank 1, Sensor 2).” The PCM detects a persistently high voltage from the Bank 1, Sensor 2 downstream O2 sensor, indicating a short to voltage, contamination, or a rich condition at the post-catalyst sensor. This code is most commonly reported on 2007-2010 Toyota Camry, 2008-2013 Toyota Highlander, and 2003-2013 Toyota Matrix, with repair costs ranging from $150 to $1,400.
Common Causes
Typical Repair Cost
Based on 3 documented vehicle-specific issues. Actual cost depends on root cause and vehicle.
Diagnostic Tools
This is a powertrain code, so a basic OBD-II reader can read it. These read P0138.
ANCEL AD310 Classic OBD-II Scanner
by ANCEL
A simple code reader for engine (P) codes on many compatible OBD-II vehicles. It does not support every vehicle or hybrid/EV application, and it does NOT read body, chassis or network codes; confirm exact-vehicle compatibility before buying.
- Read & clear engine (P) codes
- View freeze frame data
- I/M readiness status
- No batteries or app needed
BlueDriver Pro Bluetooth Scanner
by BlueDriver
Bluetooth scanner with a companion app that reads beyond the engine module — ABS, SRS and transmission — plus manufacturer-specific codes on many vehicles.
- Enhanced diagnostics (ABS, SRS, transmission)
- Repair Reports with verified fixes
- Smog check readiness
- Free app (iOS & Android)
LAUNCH CRP123X V3.0 Elite OBD-II Scanner
by LAUNCH
Handheld scanner covering the four major systems (engine, transmission, ABS, SRS) with live data streaming and graphing.
- Engine, transmission, ABS, SRS diagnostics
- Live data stream & graphing
- AutoVIN for vehicle identification
- Free lifetime updates via Wi-Fi
Autel MaxiCOM MK808S Diagnostic Tool
by Autel
Shop-level tablet with all-system coverage and bi-directional control, so you can command a module rather than only read it.
- All-system diagnostics (25+ modules)
- Bi-directional control & active tests
- Oil reset, EPB, BMS, TPMS, injector coding
- 7-inch touchscreen with Android OS
What you can do yourself, and what needs a shop
Reading the code, clearing it, and watching whether it returns is a driveway job with the right scanner. These steps are not:
- Module programming or software updates — needs the manufacturer software or a J2534 pass-through with a paid subscription.
- Replacing a control module — most are VIN-programmed and immobilizer-registered, so a new one does nothing until it is coded to your car.
- Airbag/SRS component work — a stored fault can deploy a live device.
If the vehicle is still under warranty, check for an open recall or technical service bulletin before buying anything — the repair may already be covered.
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Vehicles Affected (3)
2007-2010 2GR-FE P0138/P0158/P0606 Diagnostic Gates - T-SB-0001-10
Air/Fuel Ratio Sensor Signal Stuck Lean — P2195 / P2197 with P0138 / P0158 (2GR-FE)
Catalyst Efficiency Failure (P0420) Driven by Oil Consumption and Aged O2 Sensors
FAQ
What does P0138 mean?
P0138 stands for "O2 Sensor Circuit High Voltage (Bank 1, Sensor 2)." The PCM detects a persistently high voltage from the Bank 1, Sensor 2 downstream O2 sensor, indicating a short to voltage, contamination, or a rich condition at the post-catalyst sensor.
What are the most common causes of P0138?
The most common causes of P0138 are: Faulty downstream O2 sensor, Short to voltage in signal wire, Coolant/contaminant on sensor, Rich exhaust condition, Wiring/connector fault. The specific cause varies by vehicle.
How much does it cost to fix P0138?
Repair costs for P0138 range from $150 to $1,400, depending on the vehicle and root cause.
Which vehicles are affected by P0138?
Au7o has documented P0138 across 3 vehicle models from 1 manufacturers: Toyota.
Sources (7)
- TSBToyota T-SB-0001-10 Rev1: P0138, P0158 and/or P0606 Diagnostic Tips
- ForumToyotaNation (Highlander 2nd Gen 2008-2013): A/F Sensor Issue? (P2197)
- ForumToyotaNation: CHECK ENGINE LIGHT code P2195, air fuel sensor B1S1 bad
- TSBCorrecting Toyota Air Fuel Response — Toyota service bulletin coverage for 2008-2010 Highlander P0138/P0158 with P2195/P2197
- ForumP0420 Code (Catalytic Converter) - ToyotaNation
- ForumUnrelenting P0420 remains after catalytic converter, O2 sensors replaced - GenVibe (Pontiac Vibe, Matrix twin)
- articleHow to Fix a P0420 Error Code on a Toyota Corolla - Practical Mechanic
Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.