All codes › P0139
P0139: O2 Sensor Circuit Slow Response (Bank 1 Sensor 2)
What it means
The downstream O2 sensor on bank 1 (after the catalytic converter), which monitors converter efficiency is responding too slowly.
Severity: Low Emissions-only; aging downstream sensor.
Common causes
- Aged sensor
- Exhaust leak
- Contamination
- Wiring resistance
Most common causes first. Exact causes vary by make, model and engine.
Can I fix it myself?
Often DIY. Replace the sensor; reset monitors with a drive cycle.
Repair cost
SEEDED ESTIMATE Roughly $70–$330
Most likely repair: oxygen sensor. Diagnosis fees, taxes and other causes are not included.
| Line | Low | High | Basis |
|---|---|---|---|
| Oxygen sensor | $36 | $168 | Typical listed retail range, source |
| Labor 0.3–1 hr | $30 | $160 | $100–$160/hr, shop survey |
⚠️ This is an editorial placeholder range for this type of repair. It is not based on real invoices or licensed pricing data yet. Real ranges will appear here once enough reader invoices for P0139 are verified.
Verified reader invoices for P0139: 0. Share your repair bill to help build real costs.
Tools that can read P0139
- ScanFixAI: Pro $29.99/mo or $249.99/yr
- OBDAI: Annual PRO bundle $299
- BlueDriver Pro Next-Gen: $119.95 list ($99.95 sale seen)
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