Failed Bank 2 Sensor 2 oxygen sensor or its internal heater (both sources). Open in the heater power circuit or ground circuit, such as a blown fuse or broken wire (OBD-Codes.com); defective sensor wiring or circuit problem (RepairPal). Signal tracking in the connector from oil or moisture contamination (OBD-Codes.com). Engine computer needs a software update (RepairPal). Failed engine computer, which is rare (both sources).

Replace the Bank 2 Sensor 2 oxygen sensor if its heater has failed (both sources). Repair an open or short in the heater power or ground circuit (both sources). Clean or repair a connector damaged by oil or moisture tracking (OBD-Codes.com). Have the engine computer's software updated if available (RepairPal); replace the computer only after the sensor and wiring have been ruled out.

P0161🌫 Emissions / oxygen sensorsDrive with caution, fix soon

P0161: O2 Sensor Heater Circuit, Bank 2 Sensor 2 (Meaning, Causes, Fixes)

Q: What does P0161 mean?

P0161 means the engine computer has found a problem in the heater circuit of the rear (downstream) oxygen sensor on bank 2, the one behind the catalytic converter. A failed sensor heater is the most common cause, but an open or short in the heater's power or ground wiring, a contaminated connector or, rarely, the engine computer can also set it. Oxygen sensors only read accurately when they are hot, so each one has a built-in electric heater that brings it up to temperature quickly. RepairPal says the heater keeps the sensor at an operating temperature of about 300 to over 600 degrees F, and that P0161 sets when the computer decides the heating circuit is using too little or too much electrical power. OBD-Codes.com describes the same thing as the computer detecting an excessive current draw, or an open or short in the circuit powering the heater. Bank 2 Sensor 2 is the sensor behind the catalytic converter on the side of the engine that does not contain cylinder 1, so this code only applies to engines with two banks, such as V6 and V8 engines. The computer uses this rear sensor to check how well the catalytic converter is working. Note that OBD-Codes.com's page title calls P0161 'O2 Sensor Circuit Low Voltage', but its own description, RepairPal and the generic code definition all describe a heater circuit fault; the low-voltage code for this sensor is P0157. P0141 is the same heater code for the rear sensor on bank 1, and P0155 is the heater code for the front sensor on bank 2.

Q: Can I keep driving with P0161?

Drive with caution, fix soon. Usually drivable for now, but get it checked soon. RepairPal rates P0161 Moderate: not an immediate threat to safety or the car, but it should be diagnosed within a reasonable time. OBD-Codes.com gives no severity rating and says there will likely be no obvious symptoms other than the check engine light. RepairPal lists possible rough running, worse fuel economy and the engine dying, so get it looked at sooner if the engine isn't running right.

Reviewed 2026-10-23 · Based on 2 cited source(s)

What P0161 means

Oxygen sensors only read accurately when they are hot, so each one has a built-in electric heater that brings it up to temperature quickly. RepairPal says the heater keeps the sensor at an operating temperature of about 300 to over 600 degrees F, and that P0161 sets when the computer decides the heating circuit is using too little or too much electrical power. OBD-Codes.com describes the same thing as the computer detecting an excessive current draw, or an open or short in the circuit powering the heater. Bank 2 Sensor 2 is the sensor behind the catalytic converter on the side of the engine that does not contain cylinder 1, so this code only applies to engines with two banks, such as V6 and V8 engines. The computer uses this rear sensor to check how well the catalytic converter is working. Note that OBD-Codes.com's page title calls P0161 'O2 Sensor Circuit Low Voltage', but its own description, RepairPal and the generic code definition all describe a heater circuit fault; the low-voltage code for this sensor is P0157. P0141 is the same heater code for the rear sensor on bank 1, and P0155 is the heater code for the front sensor on bank 2.

Severity: can I keep driving?

Drive with caution, fix soon

Usually drivable for now, but get it checked soon. RepairPal rates P0161 Moderate: not an immediate threat to safety or the car, but it should be diagnosed within a reasonable time. OBD-Codes.com gives no severity rating and says there will likely be no obvious symptoms other than the check engine light. RepairPal lists possible rough running, worse fuel economy and the engine dying, so get it looked at sooner if the engine isn't running right.

Common symptoms

Check engine light on (both sources)
Often no other obvious symptoms (OBD-Codes.com; RepairPal says this happens in some unusual cases)
Rough idle or rough running (RepairPal)
Worse fuel economy, which RepairPal puts down to the computer running in a 'limp home' mode
Engine dying (RepairPal)

Likely causes

Roughly most to least common, based on the sources below. Your vehicle may differ.

Failed Bank 2 Sensor 2 oxygen sensor or its internal heater (both sources)
Open in the heater power circuit or ground circuit, such as a blown fuse or broken wire (OBD-Codes.com); defective sensor wiring or circuit problem (RepairPal)
Signal tracking in the connector from oil or moisture contamination (OBD-Codes.com)
Engine computer needs a software update (RepairPal)
Failed engine computer, which is rare (both sources)

Diagnostic steps you can do

⚠ Before you start

Work on a cool engine, parked on level ground with the parking brake set. Never work under a car supported only by a jack.

Read all stored codes and freeze-frame data. If other heater codes are set for several sensors at once, suspect a shared fuse or power feed before replacing sensors.
Find the Bank 2 Sensor 2 sensor behind the catalytic converter and inspect its harness and connector for melted, chafed or broken wires and for oil or moisture inside the connector (OBD-Codes.com mentions connector contamination).
With the key on, check that the heater has battery voltage and a good ground at the connector, as RepairPal's technician steps describe. Use a high-impedance digital meter.
Unplug the sensor and measure the heater's resistance across its heater pins, comparing it with the specification in a repair manual for your vehicle. An open heater means the sensor needs replacing.
Clear the code and drive. If it returns right away, the fault is still present; if it never returns, it may have been an intermittent connection, so wiggle-test the harness.

Typical fixes

Replace the Bank 2 Sensor 2 oxygen sensor if its heater has failed (both sources)
Repair an open or short in the heater power or ground circuit (both sources)
Clean or repair a connector damaged by oil or moisture tracking (OBD-Codes.com)
Have the engine computer's software updated if available (RepairPal); replace the computer only after the sensor and wiring have been ruled out

Repair costs vary widely by vehicle, region, parts brand and shop, so we don't quote prices. Get a written estimate after diagnosis.

🛠 When to call a pro

The heater has power, ground and the right resistance, but the code keeps coming back
A new sensor doesn't fix it, which points to wiring or the engine computer's heater control
You need the heater on-times checked against the manufacturer's diagnostic procedure, as RepairPal describes for technicians
The engine is running rough or stalling
The car failed an emissions test

Where to buy

Plain search links. Always match parts to your exact year, make, model and engine.

OBD2 scanners on Amazon Parts at Advance Auto Parts catalog at RockAuto

FAQs

Can I drive with P0161?

Usually, for a while. RepairPal rates it Moderate, and OBD-Codes.com says there will likely be no symptoms other than the check engine light. Get it checked sooner if the engine runs rough or stalls.

Does P0161 mean I need a new oxygen sensor?

Often. A failed heater inside the sensor is the most common cause, but check the fuse, power and ground wiring and the connector first, since OBD-Codes.com and RepairPal both list wiring problems.

Where is the Bank 2 Sensor 2 oxygen sensor?

It is in the exhaust behind the catalytic converter on bank 2, the side of the engine that does not have cylinder 1. Only engines with two banks, such as V6 and V8 engines, have a bank 2.

What's the difference between P0161 and P0141?

They mean the same thing on different sides of the engine. P0141 is a heater circuit fault in the rear sensor on bank 1, and P0161 is the same fault on bank 2.

How much does it cost to fix P0161?

Neither source gives a repair cost for P0161. It depends on whether the fix is a new sensor or a wiring repair, so get it diagnosed first.

Sources

Last reviewed 2026-10-23. Code definitions and repair steps can vary by manufacturer. Confirm with your vehicle's service information.