O2 sensor sample error — exhaust composition at sensor not as expected, common on turbo and GDI engines.
Common symptoms
- Check engine light
- Poor fuel trim
Typical causes
- Exhaust leak before O2
- Failed upstream O2
- Boost leak affecting exhaust pulse
- Rich/lean extreme condition
What scanner do you need?
Full-system scanner (engine, ABS, SRS, transmission, service resets)
Use live data and freeze frame to confirm the fault before replacing parts. ABS, SRS, and network U-codes usually require a full-system scanner.
Diagnostic tips
- Record freeze frame data when the code first sets
- Clear the code only after fixing the root cause
- Check for related pending codes that point to a common issue
- Verify battery voltage is above 12.4V before chasing sensor codes