P0136 Code: O2 Sensor Circuit Malfunction (Bank 1 Sensor 2)
🟢 Low severity · drivable
Safe to drive — this downstream sensor only monitors the catalytic converter, so it won't affect drivability.
What P0136 means
The bank 1 downstream oxygen sensor (the one after the catalytic converter) isn't producing a usable signal. Unlike the upstream sensor, this one doesn't control the fuel mixture — it only watches the catalytic converter, so the symptom is usually just the check engine light and a failed emissions test.
Symptoms
- Check engine light on
- Possible failed emissions test
- Usually no driving symptoms
Common causes
- most common: Faulty downstream oxygen sensor
- common: Exhaust leak near the sensor
- less common: Damaged wiring or connector
How to fix it
| Fix | DIY? | Typical cost |
|---|---|---|
| Replace the bank 1 downstream oxygen sensor | Yes | $60–200 |
| Repair an exhaust leak near the sensor | Mechanic | $50–200 |
Frequently asked questions
What's the difference between sensor 1 and sensor 2?
Sensor 1 (upstream) controls the fuel mixture; sensor 2 (downstream) only monitors the catalytic converter. A P0136 doesn't affect how the car drives.
Can I drive with a P0136?
Yes. It's an emissions-monitoring fault, not a drivability problem.
How much does it cost to fix P0136?
Typically $60–$200 for a downstream oxygen sensor.
Related codes
P0137
P0137 Code: O2 Sensor Circuit Low Voltage (Bank 1 Sensor 2)
P0138P0138 Code: O2 Sensor Circuit High Voltage (Bank 1 Sensor 2)
P0420P0420 Code: Catalyst System Efficiency Below Threshold (Bank 1)
Related guide: MAF Sensor Replacement Cost →
Updated 2026-08. This page is informational and not a substitute for professional diagnosis.