AutoCodes – Mazda – P0136 Mazda

P0136 Mazda Code - HO2S12 Circuit Fault

Quick Answer

The heated oxygen sensor 2 (HO2S), after three way catalyst (manifold), monitors the oxygen level in the exhaust gas on each bank. Common causes include Faulty Rear Heated Oxygen Sensor Bank 1, Rear Heated Oxygen Sensor Bank 1 harness is open or shorted, Rear Heated Oxygen Sensor Bank 1 circuit poor electrical connection. Severity is Moderate - service should be scheduled soon. The vehicle may still be drivable for short trips if it runs normally, but avoid hard driving and repair it soon.

What it means: P0136 Mazda indicates HO2S12 Circuit Fault.
Common causes: Common causes include Faulty Rear Heated Oxygen Sensor Bank 1, Rear Heated Oxygen Sensor Bank 1 harness is open or shorted, Rear Heated Oxygen Sensor Bank 1 circuit poor electrical connection.
Severity: Moderate - service should be scheduled soon.
Can I drive?: The vehicle may still be drivable for short trips if it runs normally, but avoid hard driving and repair it soon.

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Code Popularity 16,610

How popular is this code, among other codes? Low

Repair Importance Level

Moderate (Service soon) (2 / 3)

Repair Difficulty Level

Intermediate (2 / 3)

What is this?

Table of contents Created and updated by William Orellana on Jun 14, 2020

Description
Step-by-Step Diagnostic Guide
Possible Causes
How To Fix
Tech Notes
Cost to Diagnose
FAQs
Comments
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Code P0136 Mazda Description

The heated oxygen sensor 2 (HO2S), after three way catalyst (manifold), monitors the oxygen level in the exhaust gas on each bank. For optimum catalyst operation, the air fuel mixture (air-fuel ratio) must be maintained near the ideal stoichiometric ratio. The HO2S output voltage changes suddenly in the vicinity of the stoichiometric ratio. The Engine Control Module (ECM) adjusts the fuel injection time so that the air-fuel ratio is nearly stoichiometric. The HO2S generates a voltage between 0.1 and 0.9 V in response to oxygen in the exhaust gas. If the oxygen in the exhaust gas increases, the air-fuel ratio becomes Lean. The ECM interprets Lean when the HO2S voltage is below 0.45 V. If the oxygen in the exhaust gas decreases, the air-fuel ratio becomes Rich. The ECM interprets Rich when the HO2S voltage is above 0.45 V.

OBDII Code P0136 Mazda - HO2S12 Circuit Fault - AutoCodes.com — P0136 Mazda Code - HO2S12 Circuit Fault

What does this mean?

What are the Possible Causes of the DTC P0136 Mazda?

Faulty Rear Heated Oxygen Sensor Bank 1
Rear Heated Oxygen Sensor Bank 1 harness is open or shorted
Rear Heated Oxygen Sensor Bank 1 circuit poor electrical connection
Inappropriate fuel pressure
Faulty fuel injectors
Intake air leaks may be faulty
Exhaust gas leaks

How to Fix the DTC P0136 Mazda?

Review the 'Possible Causes' above and visually examine the corresponding wiring harness and connectors. Check for damaged components and inspect connector pins for signs of being broken, bent, pushed out, or corroded.

What does this mean?

Code Tech Notes

Replacing the Rear Heated Oxygen Sensor Bank 1 usually takes care of the problem.

What is the Cost to Diagnose the Code?

Labor: 1.0

To diagnose the P0136 Mazda code, it typically requires 1.0 hour of labor. Rates vary by location, vehicle, and shop. Many shops charge between $80–$150 per hour; dealerships and metro areas may be higher, independents may be lower.

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About the author: William Orellana is a Master Mechanic and Mechanical Engineer with over 30 years of experience diagnosing and repairing vehicles. Learn more about his background.

Frequently Asked Questions about P0136 Mazda Code

1. What does the OBDII code P0136 mean on a Mazda?

P0136 indicates a fault in the circuit for the downstream oxygen sensor (HO2S12) located after the catalytic converter, typically related to voltage or signal issues.

2. What are the symptoms of P0136 on a Mazda?

Common symptoms include the check engine light turning on, decreased fuel efficiency, rough idling, and potential issues passing emissions tests.

3. What causes the P0136 code on a Mazda?

Possible causes include a faulty oxygen sensor, damaged wiring or connectors, exhaust leaks, or issues with the engine control module (ECM).

4. Can I drive my Mazda with the P0136 code?

While the vehicle may still be drivable, ignoring the code can lead to reduced fuel efficiency, increased emissions, or damage to the catalytic converter over time.

5. How do I fix the P0136 code on a Mazda?

Repairs may include replacing the downstream oxygen sensor, repairing damaged wiring, checking for exhaust leaks, or updating the ECM software if required.

6. How do I diagnose the cause of a P0136 code in my Mazda?

Diagnosis involves using a scan tool to monitor oxygen sensor readings, inspecting wiring and connectors for damage, and visually checking for exhaust system leaks.

7. How much does it cost to fix the P0136 code on a Mazda?

Repair costs can range from $100 to $300, depending on whether the oxygen sensor needs replacement or if wiring or other components require repairs.

8. Is the P0136 code specific to Mazdas?

No, P0136 is a generic OBDII code applicable to all vehicles with OBDII systems, but troubleshooting steps and parts may vary between models.

9. What tools are needed to fix the P0136 code on a Mazda?

You may need a scan tool, a digital multimeter for testing wiring, and basic hand tools to replace the oxygen sensor or repair damaged components.

10. Can a dirty air filter cause the P0136 code on my Mazda?

A dirty air filter is unlikely to directly cause P0136, but it can affect overall engine performance, which might indirectly contribute to emissions system issues.