P0136
Low SeverityO2 Sensor Circuit (Bank 1, Sensor 2)
Emissions System
P0136 — Instant Answer
O2 Sensor Circuit (Bank 1, Sensor 2)
Severity: LOW SEVERITY
Meaning: General fault with the downstream (post-cat) O2 sensor on bank 1. This sensor monitors catalytic converter efficiency.
Safe to drive? Usually yes with caution, but confirm root cause before long trips.
Estimated repair cost: $25 - $80
Most common causes:
- 1. Faulty downstream O2 sensor (35-45% of cases)
- 2. Wiring damage from exhaust heat (10-25% of cases)
- 3. Contaminated sensor (10-25% of cases)
Symptoms
- ⚠️Check engine light
- ⚠️Failed emissions test
- ⚠️No driveability symptoms
Related Symptoms
Common Causes
How to Diagnose P0136
- 1Check sensor connector and wiring
- 2Monitor sensor voltage (should be steady ~0.4-0.6V)
- 3Compare to upstream sensor behavior
- 4Replace if erratic
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Related Resources
Repair guides, symptom pages, and wiring diagrams related to P0136.
Related Symptoms
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Related Codes
Downstream O2 sensor on bank 1 is reading too low. Could indicate a failing sensor or a lean exhaust condition.
Downstream O2 sensor bank 1 is stuck at a high voltage. Usually a failed sensor.
The heater in the downstream O2 sensor on bank 1 has failed.
Frequently Asked Questions
- Does the downstream O2 sensor affect performance?
- No — it only monitors the catalytic converter. Performance and fuel economy are not affected.
- What should downstream O2 voltage be?
- A healthy downstream O2 should read a fairly steady 0.4-0.7V. Rapid oscillation like the upstream sensor indicates a failing catalytic converter.
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Author & Review
Written by AllOEMManuals Editorial Team. Reviewed by ASE-certified technicians and updated with factory-reference checks for fitment-sensitive steps.
This guide was drafted with AI assistance and reviewed for accuracy by a human editor.
Last updated: 2026-05-07