OBD-II Code · Sensors
P0163
O2 Sensor Circuit Low Voltage (Bank 2 Sensor 3)
Severity
low
Lowest on our scale. Fix it when convenient.
Can you drive it
Only if running normally
A short trip to a shop may be reasonable if the light is steady and the car runs normally. Stop safely for a flashing light, severe shaking, overheating, loss of power, or another urgent warning. The code alone cannot confirm safety.
Indicative cost (USD)
$200–$500
Varies by vehicle, diagnosis, parts, and local labor. This is not a repair quote.
B2S3 sensor stuck low.
How a shop works this
Work from evidence to part, not the other way round. A code names a circuit or a symptom; it does not name the part that failed.
Note every code that is set, not just this one.
Codes that appear together usually narrow the cause faster than any one of them read alone.
Read the freeze frame — the conditions the fault was recorded under.
Cold or warm, idle or load, road speed and engine speed. A fault that only appears cold is a different fault from one that only appears under load, even with the same code on the scanner.
Confirm the fault is current rather than history.
Clear the code and see whether it returns under those same conditions. A code that does not come back may have been logged during a repair, a flat battery, or a bad connection that has since been disturbed.
Then work the likely-causes list in the order shown.
That order is what a shop checks first for this code — wiring and connections before the component they run to, because a connector costs nothing to inspect and is a common answer.
If the code comes back after a repair, the underlying fault is still there. That is the point to bring in a scanner with live data and freeze-frame, or a shop that has one.
Common symptoms
- Check engine light
- Possible fuel trim adaptation
Likely causes
- Failed sensorMost common
- Exhaust leak
- Wiring short
Read the full diagnostic procedureP0163 sets when the Bank 2 Sensor 3 signal voltage stays below approximately 0.10V for longer than the diagnostic window (typically 20-90 seconds dep…
P0163 sets when the Bank 2 Sensor 3 signal voltage stays below approximately 0.10V for longer than the diagnostic window (typically 20-90 seconds depending on platform). A narrowband post-cat sensor pinned low almost always means the signal wire is shorted to ground, the sensor element has internally shorted, or the sensor is reading genuinely lean from an upstream exhaust leak that pulls fresh air in before the sensor.
Cheapest first
- unplug the sensor and watch live data -- if the PCM-displayed voltage immediately jumps to 0.45V bias with the sensor disconnected, the wiring back to the PCM is fine and the sensor element is internally shorted (replace sensor).
- If the displayed voltage stays at or near 0.0V with the sensor unplugged, the signal wire is shorted to ground between the sensor connector and the PCM -- usually a chafed wire against the exhaust heat shield or transmission bellhousing.
- Before condemning the sensor, smoke-test the exhaust upstream of it: a leaking gasket at the cat flange or a hairline crack in the manifold will pull atmospheric oxygen past the sensor on overrun and lock the reading lean.
- Caveat: chasing a lean post-cat code by adding fuel trim or changing the upstream sensor is a $600 detour -- a $15 exhaust gasket is the actual fix more often than mechanics admit.
Vehicle-specific patterns2004-2010 Ford F-150 5.4L 3V -- driver-side (bank 2) exhaust manifold studs back out and the resulting leak pulls the post-cat sensor lean, Ford TSB…
- 2004-2010Ford F-150 5.4L 3V -- driver-side (bank 2) exhaust manifold studs back out and the resulting leak pulls the post-cat sensor lean, Ford TSB 11-9-3 covers stud and gasket replacement.
- 2007-2013Chevy Silverado 5.3L L83 -- bank 2 sensor 3 wire chafes through against the transmission cooler line return, signal shorts to ground, GM bulletin PI0691.
- 2006-2012Toyota Tundra 4.7L 2UZ-FE -- bank 2 exhaust manifold cracks near the flange and creates the false-lean condition.
- 2008-2013Dodge Durango 4.7L PowerTech -- post-cat sensor element fails internally shorted on high-mileage units, replacement is the only fix once harness clears.
Estimated repair$140 to $520.
Look up another code
P0163 — frequently asked
What does a P0163 code mean?
B2S3 sensor stuck low.
What causes a P0163 code?
Common causes: Failed sensor; Exhaust leak; Wiring short.
What are the symptoms of a P0163 code?
Typical symptoms: Check engine light; Possible fuel trim adaptation.
Is it safe to drive with a P0163 code?
Only if running normally. A short trip to a shop may be reasonable if the light is steady and the car runs normally. Stop safely for a flashing light, severe shaking, overheating, loss of power, or another urgent warning. The code alone cannot confirm safety. Estimated repair: $200-$500.
How do I diagnose a P0163 code?
Work from evidence to part, not the other way round. A code names a circuit or a symptom; it does not name the part that failed. 1. Note every code that is set, not just this one. 2. Read the freeze frame — the conditions the fault was recorded under. 3. Confirm the fault is current rather than history. 4. Then work the likely-causes list in the order shown.
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