P1129 Code - Downstream Oxygen Sensors Swapped from Bank to Bank

Quick Answer

The diagnostic code P1129 indicates that the downstream oxygen sensors on the vehicle have been swapped from bank to bank. Common causes include Incorrect installation of oxygen sensors during maintenance or repairs, Faulty wiring or connectors leading to sensor swapping, Aftermarket modifications causing sensor misplacement. Severity is High - diagnose this code as soon as possible. Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.

What it means

P1129 indicates Downstream Oxygen Sensors Swapped from Bank to Bank .

Common causes

Common causes include Incorrect installation of oxygen sensors during maintenance or repairs, Faulty wiring or connectors leading to sensor swapping, Aftermarket modifications causing sensor misplacement.

Severity

High - diagnose this code as soon as possible.

Can I drive?

Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.

• Description
• Common Causes
• Symptoms
• How To Fix
• Cost to Fix
• FAQs
• Comments
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Common Causes of P1129

Symptoms of P1129

How to Fix P1129

Cost to Fix P1129

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Code P1129 Information for Specific Makes

• P1129 Acura — Manifold Absolute Pressure Sensor Circuit Higher Than Expected
• P1129 Audi — Long Term Fuel Trim B2 System Too Rich
• P1129 Chrysler — Closed Loop Fueling Not Achieved Bank 2
• P1129 Dodge — Closed Loop Fueling Not Achieved Bank 2
• P1129 Ford — Downstream Oxygen Sensors Swapped from Bank to Bank
• P1129 Honda — Manifold Absolute Pressure Sensor Circuit Higher Than Expected
• P1129 Jeep — Closed Loop Fueling Not Achieved Bank 2
• P1129 Land Rover — HO2S Swapped Sensors Left Side To Right Side
• P1129 Lexus — Electric Throttle Control System Malfunction
• P1129 Lincoln — Downstream Oxygen Sensors Swapped from Bank to Bank
• P1129 Mercury — Downstream Oxygen Sensors Swapped from Bank to Bank
• P1129 Mitsubishi — Closed Loop Fueling Not Achieved Bank 2
• P1129 Toyota — Electric Throttle Control System Malfunction
• P1129 Volkswagen — Long Term Fuel Trim B2 System Too Rich

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 P1129 Code

1. What are the common symptoms of OBDII code P1129 related to downstream oxygen sensors swapped from bank to bank?

- Common symptoms include poor fuel economy, rough idling, engine misfires, and possibly a check engine light illuminated on the dashboard.

2. What could cause downstream oxygen sensors to be swapped from bank to bank triggering code P1129?

- The most common cause is a wiring issue, where the sensor signals are crossed or incorrectly connected during installation or repair.

3. How serious is OBDII code P1129 and should it be addressed immediately?

- While the vehicle may still be drivable with this code, it is important to address it promptly to prevent potential damage to the catalytic converter and ensure optimal engine performance.

4. Can I continue driving my vehicle with OBDII code P1129 until I can get it fixed?

- It is generally not recommended to drive the vehicle for an extended period with this code present, as it can lead to decreased fuel efficiency and potential long-term damage to the engine components.

5. What is the typical repair process for resolving OBDII code P1129 related to downstream oxygen sensors swapped from bank to bank?

- The repair usually involves identifying the swapped sensors, correcting the wiring connections, and clearing the error code using an OBDII scanner.

6. How can I prevent downstream oxygen sensors from being swapped from bank to bank in the future?

- To prevent this issue, always double-check the sensor connections when replacing them and follow the manufacturer's guidelines for sensor installation.

7. Are there any DIY tips for troubleshooting OBDII code P1129 before taking the vehicle to a professional mechanic?

- You can visually inspect the sensor connections, check for any visible wiring issues, and ensure that the correct sensors are installed in their designated locations.

8. Will resetting the error code using an OBDII scanner fix the issue permanently?

- Simply clearing the error code may temporarily turn off the check engine light, but if the underlying wiring issue causing the sensors to be swapped is not fixed, the code is likely to reappear.

9. Is it possible for a faulty downstream oxygen sensor to trigger code P1129 even if the sensors are not physically swapped?

- Yes, a malfunctioning downstream oxygen sensor can sometimes send incorrect signals that mimic the effects of swapped sensors, triggering code P1129.

10. How much should I expect to pay for professional repairs related to OBDII code P1129 due to downstream oxygen sensors swapped from bank to bank?

- The cost of repairs can vary depending on the extent of the wiring issue and the labor rates of the mechanic, but it is generally a relatively straightforward and affordable fix compared to other engine problems.