P0162
O2 Sensor Circuit Malfunction (Bank 2 Sensor 3)P0162 is a generic OBD-II powertrain diagnostic trouble code: O2 Sensor Circuit Malfunction (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 P0162 means
P0162 is stored when the PCM detects a malfunction in the oxygen sensor circuit for Bank 2, Sensor 3 — the third O2 sensor in the exhaust stream on the side of the engine opposite cylinder number 1. The PCM typically sets this code when the sensor signal is outside the 0.1–0.9 V operating range, stuck at a fixed voltage, or completely inactive over an extended monitoring period. It is the Bank 2 counterpart to P0146 (Bank 1, Sensor 3).
A third oxygen sensor (Sensor 3) is not present on most standard four-cylinder or single-bank engines. It is found on vehicles with dual catalytic converters in series, certain Y-pipe or twin-exhaust layouts, or inline-6 configurations where regulators require independent downstream monitoring of each catalyst stage. If your vehicle does not have three exhaust sensors per bank, consult the vehicle-specific wiring diagram to confirm the sensor's physical location before beginning diagnosis.
Because B2S3 is a post-catalyst monitor rather than a fuel-control input, P0162 rarely causes perceptible drivability changes. The engine management system will not alter fuel delivery based on this sensor's signal. However, the PCM can no longer assess the efficiency of the second catalytic converter on Bank 2, and related catalyst efficiency codes (P0430 or similar) may set concurrently. Wiring faults and sensor contamination are the most common root causes at this downstream position.
Common causes
Most-frequently reported root causes when P0162 is logged.
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1
Failed O2 sensor element — the zirconia cell is contaminated by oil, coolant, or carbon and can no longer generate a valid signal.
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2
Open circuit on the sensor signal wire — a break, corroded pin, or rodent damage prevents any voltage from reaching the PCM.
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3
Short to ground on the signal wire — pulls the signal to zero volts and triggers an out-of-range fault.
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4
Damaged or disconnected sensor harness connector — vibration or heat cycling can cause intermittent loss of contact at the downstream location.
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5
Exhaust leaks near the sensor admitting false air — can bias the signal and prevent normal switching.
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6
Engine oil consumption introducing oil vapour into the exhaust — progressively poisons the sensor element.
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7
Failed PCM input circuit — rare, but a damaged internal input can read the sensor as inactive even if the sensor is functioning.
Symptoms drivers notice
How to diagnose P0162
A typical diagnostic flow when this code is present.
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1
Scan for all DTCs; record whether P0430 or other catalyst codes are present alongside P0162.
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2
With the engine warm and at idle, observe B2S3 live data — the signal should hover near 0.6–0.8 V with minor variation; a completely fixed or zero voltage reading confirms the fault.
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3
Visually inspect the sensor connector, wiring harness, and routing for heat damage, corrosion, chafing, or rodent damage; the long harness run to the third sensor is vulnerable at the underbody.
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4
With the sensor disconnected, verify signal wire continuity from the sensor connector to the PCM and check for shorts to ground using a multimeter.
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5
Inspect the exhaust pipe for cracks or loose joints upstream of the sensor that could be admitting air.
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6
Check the engine for signs of oil consumption (blue smoke, low oil level) that could be contaminating the sensor element.
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7
Replace the sensor if wiring is confirmed good; retest with scan tool live data after a complete warm drive cycle to verify the signal is now present and stable.
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
My car only has two O2 sensors per bank — why is P0162 set?
P0162 can only set on vehicles equipped with a third downstream oxygen sensor on Bank 2. If your vehicle does not physically have this sensor, the code may indicate a wiring short or PCM fault affecting the input channel. Consult the vehicle-specific sensor map before replacing any parts.
Is P0162 related to P0430 (catalyst efficiency Bank 2)?
Yes, indirectly. P0162 means the third sensor's signal is faulty, which prevents the PCM from calculating catalyst efficiency for Bank 2. If P0162 clears but P0430 then appears, the catalyst itself may be degraded. Address P0162 first, then re-evaluate catalyst performance.
Can engine oil consumption cause P0162?
Yes. Burning oil introduces phosphorus and carbon compounds into the exhaust that coat the sensor's zirconia element and render it inactive. If the sensor is found contaminated with a grey or white coating, inspect the engine for valve stem seal or piston ring wear before fitting a replacement.
Is Bank 2 Sensor 3 expensive to replace?
The sensor itself is typically similar in cost to other downstream O2 sensors, but its location deep in the underbody exhaust system can make access and removal labour-intensive, especially on vehicles with a Y-pipe or twin-exhaust layout. Rounded or seized sensor threads are common at this position due to heat and age.
Disabling P0162 in software
RaceTune can permanently disable P0162 — 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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