P0164
O2 Sensor Circuit High Voltage (Bank 2 Sensor 3)P0164 is a generic OBD-II powertrain diagnostic trouble code: O2 Sensor Circuit High Voltage (Bank 2 Sensor 3). 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 P0164 means
P0164 is stored when the PCM detects that the signal voltage from the oxygen sensor at Bank 2, Sensor 3 — the third O2 sensor in the Bank 2 exhaust stream, located downstream of the second catalytic converter — remains above roughly 0.9 V for longer than the calibrated threshold. A healthy zirconia-type O2 sensor oscillates between approximately 0.1 V and 0.9 V; a reading stuck at the upper rail indicates the sensor or its wiring is producing an abnormally high signal.
The most common hardware cause is an internal short within the sensor itself — contamination from silicone-based sealants, oil ash, or coolant can alter the sensor's electrochemical behaviour and bias the output high. A short to battery or reference voltage in the signal wire, or corrosion at a connector that introduces leakage current, will produce the same fault without any sensor failure. The heater circuit and signal circuit share a common connector, so a damaged harness at the bung exit is a frequent culprit.
Because B2S3 is a downstream (post-catalyst) monitor, its primary role is catalyst efficiency monitoring rather than closed-loop fuelling control. P0164 on its own typically does not cause drivability problems; the MIL illuminates and fuel economy may dip slightly as the PCM switches to a default open-loop strategy for that bank's catalyst monitor. Addressing it promptly is still advisable to maintain OBD readiness and pass emissions testing.
Common causes
Most-frequently reported root causes when P0164 is logged.
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1
Internal short or contamination within the Bank 2 Sensor 3 O2 sensor biases output voltage above the 0.9 V high threshold.
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2
Silicone-based RTV sealant, oil ash, or coolant intrusion into the sensor element raises signal voltage.
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3
Short to battery voltage or reference voltage in the sensor signal wire forces the input high at the PCM.
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4
Corroded or spread connector pins at the B2S3 harness plug create leakage current that elevates the measured voltage.
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5
Chafed or heat-damaged signal wire contacting a voltage source along the exhaust tunnel routing.
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6
Poor or missing ground for the sensor or sensor shield raises the reference potential.
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7
PCM analog input circuit fault causing misinterpretation of a normal sensor signal as high voltage.
Symptoms drivers notice
How to diagnose P0164
A typical diagnostic flow when this code is present.
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1
Connect a scan tool, retrieve all stored codes, and note any companion codes (P0141, P0161, P0420, P0430) that may indicate related faults.
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2
Visually inspect the B2S3 sensor connector and harness for corrosion, moisture, chafing against exhaust components, or heat damage.
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3
With the ignition on and engine off, back-probe the signal wire at the sensor connector; voltage should be near 0.45 V (bias voltage) — a reading at or above battery voltage confirms a short to power.
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4
Start the engine, monitor live O2 sensor voltage on the scan tool; a healthy B2S3 should settle near a steady mid-voltage (post-cat); a reading fixed at 0.9 V+ confirms the high-voltage fault.
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5
Disconnect the sensor and measure signal wire voltage to chassis ground with the ignition on — voltage present indicates a wiring short to power; repair or replace the harness section before condemning the sensor.
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6
If wiring is intact, substitute a known-good or new OEM-equivalent sensor and retest; clear the code and confirm it does not return after one full drive cycle.
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7
If the fault returns with a new sensor and verified wiring, test the PCM O2 input circuit with a signal simulator before considering PCM replacement.
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
Can I drive with a P0164 code?
Yes, short-term driving is generally safe because B2S3 is a downstream catalyst-monitor sensor, not a primary fuelling sensor. However, the OBD readiness monitor will not complete, which means you will fail an emissions inspection, and any underlying issue causing the high voltage should be investigated promptly.
Will clearing the code fix P0164?
No — clearing the code only extinguishes the MIL temporarily. If the root cause (contaminated sensor, shorted wire, or faulty PCM input) is not repaired, the code will return within one or two drive cycles once the monitor runs.
How is Bank 2 Sensor 3 different from Bank 2 Sensor 1 or 2?
Sensor 1 is the upstream (pre-catalyst) sensor used for closed-loop fuelling. Sensor 2 is the first downstream (post first cat) sensor for catalyst efficiency monitoring. Sensor 3 exists only on vehicles with a second catalytic converter on Bank 2 and monitors that second converter's efficiency — it has no direct influence on fuel delivery.
Could silicone exhaust sealant cause P0164?
Yes — using non-oxygen-sensor-safe (standard) silicone RTV near the exhaust can off-gas compounds that coat the sensor element, shift its electrochemical output high, and set P0164. Always use sensor-safe silicone and avoid applying any sealant near or downstream of O2 sensor bungs.
Disabling P0164 in software
RaceTune can permanently disable P0164 — 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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