OBD-II Code · Sensors
P0136
O2 Sensor Circuit Malfunction (B1S2)
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)
$150–$400
Varies by vehicle, diagnosis, parts, and local labor. This is not a repair quote.
Downstream O2 sensor circuit fault on bank 1.
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 emissions failure
Likely causes
- Failed downstream sensorMost common
- Wiring
- Exhaust leak
Read the full diagnostic procedureP0136 is a circuit fault on bank 1 DOWNSTREAM (B1S2) — the post-catalyst sensor.
P0136 is a circuit fault on bank 1 DOWNSTREAM (B1S2) — the post-catalyst sensor. This is the cat-monitoring sensor, not a fuel-trim sensor; on a healthy car its signal sits relatively flat at ~0.6-0.8V (narrow-band) because the cat has consumed most of the free oxygen in the exhaust stream. P0136 specifically means the signal is out-of-range implausible or the ECU can't even bias the pin to its rest voltage — distinct from P0137 (stuck low) and P0138 (stuck high).
Cheapest-first
- pull the connector and inspect for the usual downstream culprits — exhaust soot/oil migration through a leaking gasket, road salt corrosion on northern cars (this sensor sits in the worst environment on the vehicle), and rodent damage to the harness where it routes near the floor pan.
- Backprobe the signal wire at the ECU and verify the ~0.45V bias is present key-on engine-off; if it's at 0V or B+, the harness is shorted.
- Note that a P0136 alone rarely means cat failure — that's P0420 territory.
- P0136 is sensor or wiring.
Vehicle-specific patterns2005-2010 Chevy Cobalt / HHR with the 2.2L Ecotec set P0136 from a known-defective sensor lot (GM TSB 06-06-04-026 addressed early failures).
- 2005-2010Chevy Cobalt / HHR with the 2.2L Ecotec set P0136 from a known-defective sensor lot (GM TSB 06-06-04-026 addressed early failures).
- 2007-2013Toyota Tundra / Sequoia 5.7L 3UR-FE throws P0136 when the downstream harness gets pinched between the transmission crossmember and the heat shield.
- 2003-2009Nissan 350Z / G35 VQ35 sets P0136 from a chafed wire where the downstream harness crosses the rear subframe — common past 100k.
- 2008-2014Dodge Grand Caravan / Town & Country 3.6L Pentastar throws P0136 after the rear (bank 1 on this transverse V6) heat shield rusts through and exposes the sensor pigtail. Cost band: $150-$350 for downstream sensor swap (cheaper than upstream because access is usually easier); under $80 if it's harness repair.
Look up another code
P0136 — frequently asked
What does a P0136 code mean?
Downstream O2 sensor circuit fault on bank 1.
What causes a P0136 code?
Common causes: Failed downstream sensor; Wiring; Exhaust leak.
What are the symptoms of a P0136 code?
Typical symptoms: Check engine light; Possible emissions failure.
Is it safe to drive with a P0136 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: $150-$400.
How do I diagnose a P0136 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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