P0158
O2 Sensor Circuit High Voltage (Bank 2 Sensor 2)P0158 is a generic OBD-II powertrain diagnostic trouble code: O2 Sensor Circuit High Voltage (Bank 2 Sensor 2). It is logged by the engine control unit when the o2/lambda monitor detects that a specific fault threshold has been exceeded — typically resulting in the malfunction-indicator lamp (MIL / check-engine light) being illuminated.
What P0158 means
P0158 is set when the PCM detects that the Bank 2 Sensor 2 oxygen sensor signal has been continuously above approximately 1.0 V for longer than the calibrated threshold. This is the downstream (post-catalyst) O2 sensor on the bank opposite cylinder 1. A reading stuck high indicates the sensor is reporting a persistently rich exhaust condition at that point — or more commonly, that the signal wire has a short to a reference or battery voltage supply, or that the sensor element has failed and is producing an abnormally high output.
Genuine rich-condition causes — such as a leaking fuel injector or a stuck-open fuel pressure regulator on Bank 2 — can also drive P0158 as true high exhaust fuel content holds the sensor near its upper output limit. In those cases companion codes for rich fuel trim (P0175) or injector faults are typically also present. Because Bank 2 Sensor 2 is a monitoring sensor rather than a fuel-control sensor, the engine often continues to run without significant driveability complaints, but emissions compliance and catalyst monitoring are impaired.
Common causes
Most-frequently reported root causes when P0158 is logged.
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1
Failed O2 sensor element outputting a persistently high voltage (above 1.0 V) regardless of actual exhaust content.
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2
Signal wire shorted to the sensor's reference voltage or to battery supply.
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3
Sensor element contaminated by engine oil, coolant, or silicone sealant vapour, skewing the output high.
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4
Genuinely rich air-fuel mixture on Bank 2 caused by a leaking fuel injector or failed fuel pressure regulator.
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5
Damaged or melted harness insulation causing the signal wire to contact a power rail.
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6
Corroded connector pins bridging the signal circuit to a voltage source.
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7
Failed heater element causing incorrect sensor operating temperature and inaccurate output.
Symptoms drivers notice
How to diagnose P0158
A typical diagnostic flow when this code is present.
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1
Connect a scan tool, read all stored codes, and check for companion codes such as P0175 (Bank 2 rich) or fuel injector faults that would point to a genuine rich condition rather than a sensor or wiring fault.
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2
With the engine fully warm, observe Bank 2 Sensor 2 live voltage — a reading continuously above 1.0 V with no transitions to lean confirms the high-voltage fault.
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3
Inspect the Bank 2 sensor harness for chafed, melted, or pinched insulation, and check the connector for corrosion or bridged pins that could create an unintended voltage path to the signal circuit.
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4
Measure the signal wire resistance from the sensor connector to the PCM pin — look for an unintended continuity path to a voltage rail.
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5
Check long-term fuel trim on Bank 2; if trim is substantially negative (PCM pulling fuel), a genuine rich condition is likely driving the sensor high and fuel system diagnosis is needed.
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6
If wiring and fuel system checks pass, replace the O2 sensor with a correct OEM-specification unit and retest live data with the engine warm.
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7
If the fault returns with a new sensor and clean wiring, suspect PCM input circuit damage and follow manufacturer-specific PCM diagnostic procedures.
Related powertrain codes
- P0040 — Upstream Oxygen Sensors Swapped From Bank To Bank
- P0041 — Downstream Oxygen Sensors Swapped From Bank To Bank
- P0130 — O2 Sensor Circuit Malfunction (Bank 1 Sensor 1)
- P0131 — O2 Sensor Circuit Low Voltage (Bank 1 Sensor I)
- P0132 — O2 Sensor Circuit High Voltage (Bank 1 Sensor 1)
- P0133 — O2 Sensor Circuit Slow Response (Bank 1 Sensor 1)
Frequently asked questions
Does P0158 always mean the sensor needs replacing?
Not always. A wiring short to voltage can cause P0158 without any fault in the sensor itself. Always check the harness for shorts to power before replacing the sensor, otherwise a new sensor will set the same code.
Can P0158 and P0175 (Bank 2 running rich) appear together?
Yes, and when they do it usually indicates a genuine rich condition — for example a leaking injector or a failed fuel pressure regulator on Bank 2 — rather than a sensor fault. In that scenario, fixing the fuel system issue will resolve both codes.
Is P0158 the same fault as P0144, just on the other bank?
They describe the same type of fault — O2 sensor circuit high voltage — but on different banks and sensor positions. P0144 is Bank 1 Sensor 3 (a third sensor on Bank 1, found on specific multi-sensor exhaust layouts), while P0158 is Bank 2 Sensor 2 (the standard downstream sensor on Bank 2 on V-type engines). The diagnostic approach is identical.
Will P0158 cause limp mode or prevent starting?
In most cases, no. Bank 2 Sensor 2 is a downstream monitoring sensor and the PCM typically does not enforce limp mode based on this signal alone. The vehicle will usually drive normally with the MIL on, though emissions compliance will be compromised.
Disabling P0158 in software
RaceTune can permanently disable P0158 — and any other OBD-II diagnostic trouble code — on every ECU family we support. The monitor is disabled inside the ECU itself, so the fault stops being logged: the warning light stays off and the engine never enters limp mode for this code. The change is tied to your exact software version.
Software modifications affect emissions compliance and are not road-legal in many jurisdictions. RaceTune service files are intended for motorsport, off-road, and export use.
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