What causes fault code P0163?

• Most likely: Faulty Oxygen (O2) sensor Bank 2 Sensor 3 • Likely: Short to ground in the signal circuit or damaged wiring harness • Possible: Corrosion or poor connection in the sensor connector • Rare: Faulty Engine Control Unit (ECU) • Rare: Exhaust leak near the sensor causing an artificially lean reading

How do you fix fault code P0163?

STEP 1: Visually inspect the wiring and connector for Bank 2 Sensor 3. Check for melted wires against the exhaust or frayed insulation. Clean the connector. STEP 2: Check fuses for the O2 sensor heater circuit. Measure the reference voltage from the ECU (should be approx. 0.45V with the sensor unplugged). STEP 3: Use a scan tool to monitor live O2 sensor data. Artificially enrich the mixture (e.g., using propane or brake cleaner into the intake momentarily) and see if the sensor voltage rises above 0.6V. If it remains stuck low, the sensor is likely dead. STEP 4: Replace the O2 sensor (Bank 2, Sensor 3). Clear codes and perform a drive cycle.

Powertrain (Engine & Gearbox)Standard EOBD

P0163 - O2 Sensor Circuit Low Voltage (Bank 2, Sensor 3)

Q: What are the symptoms of fault code P0163?

• Check Engine Light (MIL) illuminated • No noticeable driveability issues (downstream sensor mostly monitors catalyst) • Failed emissions test • Slight decrease in fuel economy in some operating modes

Last updated:1 February 2026

Related:O2 Sensor Bank 2 Sensor 3, Engine Control Unit (ECU), Catalytic Converter, Wiring Harness

System

Powertrain (Engine & Gearbox)

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Technical Description

P0163 is set when the Engine Control Unit (ECU) detects that the Oxygen (O2) sensor voltage for Bank 2, Sensor 3 remains below a specified threshold (typically below 0.2V) for an extended period. Bank 2 refers to the side of the engine opposite cylinder #1. Sensor 3 is located downstream of the secondary catalytic converter. The ECU monitors this signal to ensure the catalyst is functioning correctly. If the sensor signal is stuck low due to a lean condition, a short to ground, or internal sensor failure, this DTC is stored.

Possible Causes

Faulty Oxygen (O2) sensor Bank 2 Sensor 3

Short to ground in the signal circuit or damaged wiring harness

Corrosion or poor connection in the sensor connector

Faulty Engine Control Unit (ECU)

Exhaust leak near the sensor causing an artificially lean reading

Symptoms

Check Engine Light (MIL) illuminated

No noticeable driveability issues (downstream sensor mostly monitors catalyst)

Failed emissions test

Slight decrease in fuel economy in some operating modes

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P0163 - O2 Sensor Circuit Low Voltage (Bank 2, Sensor 3)

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P0163 - O2 Sensor Circuit Low Voltage (Bank 2, Sensor 3)

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