Failed Bank 2 Sensor 2 oxygen sensor (both sources). Sensor wiring touching hot exhaust parts, or a short to voltage on the signal circuit (OBD-Codes.com); defective sensor wiring or circuit problem (RepairPal). Faulty oxygen sensor heater circuit (RepairPal; its technician notes say the heater circuit can bleed voltage into the signal wire). Engine actually running rich, usually with other codes present (OBD-Codes.com), or high fuel pressure (RepairPal). Holes in the exhaust that make the computer over-richen the mixture (OBD-Codes.com). Faulty engine coolant temperature sensor (RepairPal). Engine computer needs a software update (RepairPal), or a failed engine computer (both sources).

Replace the Bank 2 Sensor 2 oxygen sensor if it tests bad (both sources). Repair melted, chafed or shorted sensor wiring and reroute it away from the exhaust (both sources). Repair a faulty heater circuit that is bleeding voltage into the signal wire (RepairPal). Fix the cause of a rich condition, such as high fuel pressure or a bad coolant temperature sensor, if testing finds one (RepairPal, OBD-Codes.com). Repair exhaust holes (OBD-Codes.com). Have the engine computer's software updated if available (RepairPal); replace the computer only after the wiring has been fully checked (OBD-Codes.com).

P0158🌫 Emissions / oxygen sensorsDrive with caution, fix soon

P0158: O2 Sensor Circuit High Voltage, Bank 2 Sensor 2 (Meaning, Causes, Fixes)

Q: What does P0158 mean?

P0158 means the engine computer sees a voltage that is too high from the rear (downstream) oxygen sensor on bank 2, the one behind the catalytic converter. A bad sensor or damaged wiring touching the exhaust are common causes, but an engine that is really running rich, exhaust holes and a short to voltage in the signal wire can also set it. Bank 2 Sensor 2 is the oxygen 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 by comparing it with the front sensor. OBD-Codes.com explains that the computer supplies about 0.5 volts to the sensor, which normally varies between about 0.1 volts (lean) and 0.9 volts (rich), and that P0158 means the voltage on the signal circuit was higher than normal. It adds that rear sensors normally switch more slowly and less often than front sensors. RepairPal describes the trigger as the rear sensor voltage staying above 450 millivolts for more than two minutes, and says that time can vary by make and model. RepairPal's technician notes add that a signal that ever goes above 1 volt or below zero is enough on its own to condemn the sensor, often because the sensor's heater circuit is bleeding voltage into the signal wire. Note that RepairPal's article describes this 'rich phase' as both low oxygen and high oxygen; a high voltage reading means low oxygen (rich), which matches OBD-Codes.com. P0138 is the same high-voltage code for the rear sensor on bank 1, and P0157 is the low-voltage code for this same sensor.

Q: Can I keep driving with P0158?

Drive with caution, fix soon. Usually drivable for now, but get it checked soon. RepairPal rates P0158 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. Both sources list possible running problems (RepairPal: rough idle, worse fuel economy and the engine dying; OBD-Codes.com: power loss, intermittent misses and running rich), so get it looked at sooner if the engine isn't running right. In some cases RepairPal says the driver notices nothing at all.

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

What P0158 means

Bank 2 Sensor 2 is the oxygen 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 by comparing it with the front sensor. OBD-Codes.com explains that the computer supplies about 0.5 volts to the sensor, which normally varies between about 0.1 volts (lean) and 0.9 volts (rich), and that P0158 means the voltage on the signal circuit was higher than normal. It adds that rear sensors normally switch more slowly and less often than front sensors. RepairPal describes the trigger as the rear sensor voltage staying above 450 millivolts for more than two minutes, and says that time can vary by make and model. RepairPal's technician notes add that a signal that ever goes above 1 volt or below zero is enough on its own to condemn the sensor, often because the sensor's heater circuit is bleeding voltage into the signal wire. Note that RepairPal's article describes this 'rich phase' as both low oxygen and high oxygen; a high voltage reading means low oxygen (rich), which matches OBD-Codes.com. P0138 is the same high-voltage code for the rear sensor on bank 1, and P0157 is the low-voltage code for this same sensor.

Severity: can I keep driving?

Drive with caution, fix soon

Usually drivable for now, but get it checked soon. RepairPal rates P0158 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. Both sources list possible running problems (RepairPal: rough idle, worse fuel economy and the engine dying; OBD-Codes.com: power loss, intermittent misses and running rich), so get it looked at sooner if the engine isn't running right. In some cases RepairPal says the driver notices nothing at all.

Common symptoms

Check engine light on
Rough idle or rough running (RepairPal), or the engine losing power and missing intermittently (OBD-Codes.com)
Worse fuel economy (both sources)
Engine running rich (OBD-Codes.com)
Engine dying (RepairPal)
In some unusual cases, no noticeable symptoms (RepairPal)

Likely causes

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

Failed Bank 2 Sensor 2 oxygen sensor (both sources)
Sensor wiring touching hot exhaust parts, or a short to voltage on the signal circuit (OBD-Codes.com); defective sensor wiring or circuit problem (RepairPal)
Faulty oxygen sensor heater circuit (RepairPal; its technician notes say the heater circuit can bleed voltage into the signal wire)
Engine actually running rich, usually with other codes present (OBD-Codes.com), or high fuel pressure (RepairPal)
Holes in the exhaust that make the computer over-richen the mixture (OBD-Codes.com)
Faulty engine coolant temperature sensor (RepairPal)
Engine computer needs a software update (RepairPal), or a failed engine computer (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 rich-running codes or other oxygen sensor codes are present, work on those together, since OBD-Codes.com notes a rich engine can set P0158.
Inspect the exhaust for holes and check that the Bank 2 Sensor 2 wiring harness isn't touching or melted by the exhaust.
With the engine warmed up, watch the Bank 2 Sensor 2 voltage on a scan tool. OBD-Codes.com says a sensor stuck high, close to 1 volt, that doesn't drop or vary points to a problem with the sensor or its circuit.
With the key on and engine off, unplug the sensor and check that the heater has battery voltage and a good ground, and that the sensor ground is good (OBD-Codes.com).
OBD-Codes.com's next check is to jumper the sensor's signal wire to its ground wire on the harness side. If the scan tool now reads near zero volts, the wiring is good and the sensor is the likely fault; if it doesn't, the harness needs checking back toward the computer.

Typical fixes

Replace the Bank 2 Sensor 2 oxygen sensor if it tests bad (both sources)
Repair melted, chafed or shorted sensor wiring and reroute it away from the exhaust (both sources)
Repair a faulty heater circuit that is bleeding voltage into the signal wire (RepairPal)
Fix the cause of a rich condition, such as high fuel pressure or a bad coolant temperature sensor, if testing finds one (RepairPal, OBD-Codes.com)
Repair exhaust holes (OBD-Codes.com)
Have the engine computer's software updated if available (RepairPal); replace the computer only after the wiring has been fully checked (OBD-Codes.com)

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 code comes back after a new sensor is fitted, which points to wiring, the heater circuit or the computer
The jumper test doesn't bring the reading down and the wiring fault isn't visible, which OBD-Codes.com says can mean testing at the computer connector
You need the heater power, grounds and signal back-probed with a high-impedance meter, as RepairPal describes for technicians
The engine is running rich, losing power 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 P0158?

Usually, for a while. RepairPal rates it Moderate. OBD-Codes.com gives no rating, but both list rough running, power loss or stalling as possible symptoms, so get it checked sooner if the engine isn't running right.

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.

Does P0158 mean I need a new oxygen sensor?

Often, but not always. Both sources list the sensor first, but OBD-Codes.com also points to wiring touching the exhaust, a short to voltage, exhaust holes and a rich-running engine, so check the wiring and the jumper test before buying a sensor.

What's the difference between P0158 and P0138?

They mean the same thing on different sides of the engine. P0138 is a high-voltage reading from the rear sensor on bank 1, and P0158 is the same fault on bank 2.

How much does it cost to fix P0158?

Neither source gives a repair cost for P0158. It depends on whether the fix is a new sensor, a wiring repair or fixing a rich condition, 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.