P0138Low urgency

O2 Sensor Circuit High Voltage (Bank 1 Sensor 2)

Emission · Oxygen Sensors

✅ Safe to drive short-term. A consistently rich downstream sensor often means the catalytic converter is failing. Check for P0420 alongside this code.

What this means

The downstream Bank 1 O2 sensor voltage is persistently high (above 0.9V), indicating a rich exhaust reading. Can indicate a failing catalytic converter or a rich-running condition from the upstream system.

Likely causes

Failing catalytic converterMost common
Rich-running upstream engine conditionCommon
Failed downstream O2 sensorCommon

Estimated repair cost

Catalytic converter$400 – $2,200

Upstream fuel system repair$100 – $700

O2 sensor$80 – $250

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Frequently asked questions about P0138

What does P0138 mean?

Is P0138 serious?

Safe to drive short-term. A consistently rich downstream sensor often means the catalytic converter is failing. Check for P0420 alongside this code.

How much does it cost to fix P0138?

Repair costs for P0138 range from $400 – $2,200 depending on the root cause and your vehicle.

Can I drive with P0138?

Yes, the vehicle is safe to drive. Schedule a repair at your convenience.

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