P0143: O2 Sensor Circuit Low Voltage — Bank 1 Sensor 3
What to do
No driveability impact. An exhaust leak check is worth doing first.
What this code means
The bank 1 third sensor is reporting persistently low voltage. Given its position at the end of a long exhaust run, an air leak anywhere upstream of it will produce an honest lean reading — inspect the full length of pipework and its joints before suspecting the sensor.
Likely causes
Start here
- Exhaust leak before the sensor · moderate
- Faulty oxygen sensor · easy
Less common
- Wiring shorted to ground · moderate
- Road damage to underfloor wiring · moderate
Symptoms
Components involved
Information, not instruction
CarGeek is a reference, not a service manual. Its pages are written from public sources and from what other people have found, never from a manufacturer's own service information, so they can be wrong or incomplete for your particular vehicle. Some of what they describe carries real risk: high voltage, fuel under pressure, stored energy, hot and moving parts.
Have anything you intend to act on checked by a trained person against the manufacturer's own procedure for your vehicle. Nothing here replaces that procedure.
Community experience
Be the first to write this up
Nothing posted about this yet. Whatever you found is worth writing down — even a dead end saves someone the same afternoon.
What makes one worth reading:
- The car — make, model, year and engine. The same fault behaves differently on each.
- What you measured, not only what you replaced.
- What actually fixed it — or that nothing did, which is worth knowing too.
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