P0167 Code: O2 Sensor Heater Circuit Malfunction (Bank 2 Sensor 3) Explained

Quick Answer

• What it means: The Powertrain Control Module (PCM) has detected a malfunction or failure in the electrical heater circuit of the oxygen (O2) sensor located at Bank 2, Sensor 3.
• Severity: Low to Moderate. It is safe to keep driving in the short term, but your vehicle will likely fail an emissions test and should be repaired soon.
• Most common cause: A burnt-out or open internal heater element inside the Bank 2 Sensor 3 oxygen sensor itself.

What the P0167 code means

The official OBD-II definition for P0167 is "O2 Sensor Heater Circuit Malfunction (Bank 2 Sensor 3)."

To understand this, let's break down the components. Oxygen sensors (O2 sensors) measure the amount of unburned oxygen in your vehicle's exhaust to help the PCM adjust the air-fuel ratio and monitor the health of the catalytic converter. O2 sensors need to reach a very high operating temperature (often over 600°F) to provide accurate voltage readings.

To bring the sensors up to operating temperature quickly—especially during a cold start—modern O2 sensors have an internal electrical heater circuit. "Bank 2" refers to the side of the engine that does not contain cylinder number 1. "Sensor 3" indicates that this is the third sensor in that specific exhaust stream, typically located downstream, well past the catalytic converter (usually found on larger vehicles, heavy-duty trucks, or complex exhaust systems).

When the PCM commands the Bank 2 Sensor 3 heater to turn on, it monitors the electrical current. If it detects that the resistance is out of bounds, or if the circuit is completely open or shorted, it will trigger the P0167 code and illuminate your Check Engine Light.

Common symptoms

Because Bank 2 Sensor 3 is a downstream sensor primarily used to monitor emissions and the efficiency of the catalytic converter (rather than adjusting engine fueling), drivability issues are usually non-existent. You will typically notice:

• Illuminated Check Engine Light (MIL): This is the most obvious and often the only symptom.
• Failed emissions test: The vehicle will not pass a state smog or emissions inspection because the internal catalyst monitors cannot complete their testing sequence.
• Slightly decreased fuel economy: While rare for a Sensor 3 issue, the vehicle might stay in "open loop" slightly longer during cold starts if the PCM relies on all sensors to be ready.

Common causes

Ranked from most to least likely, the causes of a P0167 code include:

1. Faulty O2 Sensor (Bank 2 Sensor 3): The internal heating element inside the sensor degrades over time due to extreme heat and vibration, eventually burning out or breaking.
2. Damaged Wiring or Connector: The wires running to the O2 sensor are exposed to the elements, road debris, and extreme exhaust heat. Melted, chafed, or corroded wiring is incredibly common.
3. Blown O2 Sensor Heater Fuse: Many vehicles use a dedicated fuse or relay for the O2 sensor heater circuits. A short in the sensor or wiring can blow this fuse.
4. Poor Electrical Ground: The heater circuit requires a solid ground to function. Corrosion at the chassis ground point can cause an open circuit.
5. Faulty Powertrain Control Module (PCM): Extremely rare. The PCM itself may have a damaged internal driver failing to send the ground or power signal to the heater circuit.

How a technician diagnoses it

An ASE-certified technician will follow a logical, step-by-step process to pinpoint the exact cause of the P0167 code rather than just throwing parts at the vehicle:

1. Scan and verify codes: The technician connects an OBD-II scan tool to retrieve the P0167 code and checks Freeze Frame data to see the exact engine temperature, RPM, and load when the code was set. They will also look for other related heater circuit codes that might point to a shared fuse issue.
2. Inspect the fuse box: The technician will locate the fuse and relay responsible for the O2 sensor heaters. If the fuse is blown, they will check the wiring for a short to ground before replacing it.
3. Visual inspection: The vehicle is lifted, and the technician visually inspects the Bank 2 Sensor 3 O2 sensor, its pigtail connector, and the wiring harness routed along the exhaust. They look for melted plastic, pulled wires, or corrosion inside the connector pins.
4. Test the O2 sensor heater resistance: Disconnecting the B2S3 sensor, the technician uses a digital multimeter (DMM) to measure the resistance (ohms) across the two heater pins on the sensor side. A good heater element typically reads between 5 and 30 ohms (depending on the manufacturer). A bad element will read "OL" (Open Line) or infinite resistance, confirming the internal heater is broken.
5. Check the harness for power and ground: If the sensor's resistance is good, the technician turns the ignition to the ON position and tests the vehicle-side connector. There should be a 12-volt battery supply on the power wire and a good ground signal provided by the PCM on the control wire. If 12V is missing, there is a wiring or fuse issue.

Typical repair cost

Repairing a P0167 code is usually straightforward and relatively inexpensive. Costs vary depending on your vehicle's make, model, and local labor rates.

• O2 Sensor Replacement: If the sensor itself has failed, expect to pay between $150 and $350. The part usually costs $50 to $150 (always use high-quality OEM or equivalent sensors like Bosch, Denso, or NTK), and labor is typically 0.5 to 1 hour ($100 to $200), provided the sensor isn't seized in the exhaust pipe.
• Wiring Repair: If the harness is melted or chewed by rodents, a technician might splice in a new pigtail connector or repair the damaged wires. This usually costs $100 to $250 in labor.
• Fuse Replacement: If it's simply a blown fuse (and no short is found), the cost could be as low as $50 to $100 for the diagnostic time and a $2 fuse.

Can I keep driving with this code?

Yes, you can safely continue driving your vehicle with a P0167 code in the short term. Because Bank 2 Sensor 3 is a downstream emissions monitor, a failure in its heater circuit will not cause your engine to stall, misfire, or leave you stranded. However, the Check Engine Light will remain on, your vehicle will fail an emissions test, and ignoring the light means you won't be alerted if a more severe engine problem develops later. Plan to have it diagnosed and repaired at your earliest convenience.

Related codes

If you have a P0167, you might also see these related diagnostic trouble codes:

• P0161: O2 Sensor Heater Circuit Malfunction (Bank 2 Sensor 2)
• P0135: O2 Sensor Heater Circuit Malfunction (Bank 1 Sensor 1)
• P0155: O2 Sensor Heater Circuit Malfunction (Bank 2 Sensor 1)
• P0141: O2 Sensor Heater Circuit Malfunction (Bank 1 Sensor 2)

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