P0158 Code: O2 Sensor Circuit High Voltage (Bank 2 Sensor 2)
The O2 sensor after the bank 2 converter reads too high – often a short to heater power or a rich bank 2.
At a glance
Severity: Low
- Meaning
- O2 Sensor Circuit High Voltage (Bank 2 Sensor 2)
- System
- Fuel & Air Metering · Powertrain
- Safe to drive?
- Yes, short term
- Typical repair cost
- $50–$700
- DIY difficulty
- Easy
P0158 is set when the sensor behind the bank 2 catalytic converter reports a voltage above its upper limit, typically more than about 1.0 to 1.1 V, or stays stuck at a high value when the ECU expects it to drop. The clearest test of this sensor is a fuel cut on deceleration: with no fuel injected, the exhaust is almost pure air and any healthy sensor falls toward zero within seconds. A rear sensor that stays high even then is not measuring exhaust; usually its signal wire is picking up voltage from the heater feed where the four wires run together close to the hot converter, or the sensor is internally shorted. A bank 2 that genuinely runs rich, for example from a leaking injector or a misfire dumping unburned fuel into the converter, can also hold the reading near 0.9 V, but then the upstream sensor and fuel trims show it too.
Can I keep driving? Usually fine to drive while you arrange the repair. If the high reading is real, meaning bank 2 is running rich or misfiring, the converter on that side can overheat, so a flashing check engine light or a strong fuel smell means stop and get it checked.
How to read P0158
- P Powertrain
- 0 Generic (SAE)
- 1 Fuel & air metering
- 58 Specific fault
Symptoms
- Check engine light with little or no change in drivability
- Rotten-egg or fuel smell from the exhaust if bank 2 is truly rich
- Slightly worse fuel economy
- Misfire codes for bank 2 cylinders when a misfire is the cause
- Catalyst readiness monitor stays incomplete
Possible causes
Ranked by how often each cause is behind this code (editorial estimate).
- Signal wire picking up heater voltage where the harness melted near the bank 2 converter or pipe
- Bank 2 downstream sensor internally shorted or contaminated
- Bank 2 genuinely rich: leaking injector or misfire sending unburned fuel through the converter
- Water or corrosion bridging pins in the under-car connector
- Universal sensor spliced with wires crossed or wrong sensor type
- Poor sensor ground lifting the whole signal
Diagnosis step by step
Run a fuel-cut test
On a warm engine, drive at 40 mph or more and lift completely off the throttle in gear. The ECU shuts off the injectors and a good rear sensor falls below about 0.2 V within a few seconds. If bank 1's rear sensor drops and bank 2's stays above 0.8 V, the bank 2 sensor or its wiring is at fault, not the mixture.
Tools: OBD-II scanner
Check with the key on and the engine cold
A cold sensor produces almost no voltage. With the key on and the engine off, bank 2 sensor 2 should read near zero or the ECU bias. Anything over about 1 V means voltage is getting in from the heater circuit or a damaged harness.
Tools: OBD-II scanner
Measure the sensor's insulation
Unplug the sensor and, on the sensor side, measure between each heater pin and the signal pin; the reading must be open circuit. Continuity means the sensor is shorted internally and must be replaced.
Tools: Multimeter
Inspect the harness near the converter
Rear sensor wires run close to the hottest part of the exhaust, right behind the converter. Look for fused or stiff insulation and places where the harness lost its clips and settled onto the pipe or heat shield. Also open the connector and look for water or green corrosion bridging the pins.
Tools: Flashlight, Gloves
Rule out a rich or misfiring bank 2
If the sensor passes the fuel-cut test, check the bank 2 upstream sensor, long-term fuel trim and per-cylinder misfire counters. A trim near -15% on bank 2 only, or misfires on one of its cylinders, means the rear sensor is honestly reporting rich exhaust and the fix is upstream.
Tools: OBD-II scanner, Spark plug socket
Check the sensor ground
On 4-wire sensors the signal ground runs back to the ECU; on some older designs the sensor grounds through the pipe. With the engine running, the voltage drop between sensor ground and battery negative should be under about 0.1 V.
Tools: Multimeter
Where the parts are
- 1Upstream O2 sensor
- 2Catalytic converter
- 3Downstream O2 sensor
- 4Diesel particulate filter
- 5Turbocharger
Repair options & costs
| Repair | DIY? | Estimated cost |
|---|---|---|
| Repair melted rear sensor harness and re-clip it | No | $90–$260 |
| Replace bank 2 downstream O2 sensor yourself (part only) | Yes | $50–$180 |
| Replace bank 2 downstream O2 sensor at a shop | No | $150–$350 |
| Fix bank 2 misfire or leaking injector | No | $150–$700 |
Rough US estimates for parts and labor; shop rates vary by region. Not a quote.
Emissions / smog test impact
Will fail
A P0158 with the check engine light on fails an OBD-II emissions or smog check. If bank 2 is really running rich, a tailpipe test may also fail on CO or HC until the cause is fixed.
Frequently asked questions
Why is the fuel-cut test so useful?
During a fuel cut, the exhaust is essentially fresh air, so every working oxygen sensor must read lean. It's the one moment when you know exactly what the sensor should show, which makes a stuck-high sensor easy to catch.
Can P0158 make the engine run lean?
On many engines the ECU uses the rear sensor to fine-tune fueling. A false high reading can make it pull a little fuel from bank 2 over time, though the upstream sensor limits how far this goes.
Do I need a new catalytic converter?
Not for P0158 itself. A stuck-high rear sensor is a sensor or wiring fault, or a sign of a rich bank. Only if P0430 follows after the sensor is fixed should you look at the converter.
Could a misfire cause P0158?
Yes. A misfiring cylinder on bank 2 sends unburned fuel through the converter, and the rear sensor sees it as rich. Fix the misfire promptly, because burning fuel inside the converter overheats it.