MIL on and P0135 set, you are in the right place, I’m John Cunningham, a qualified mechanic, and very shortly, you’ll understand what’s going on and how you can fix it. Let’s jump in!
On this page, we’ll cover the following:
- What is the P0135 code?
- What does the oxygen sensor do?
- P0135 Symptoms
- What causes the P0135 code?
- How do you diagnose the P0135 code?
- How do you fix the P0135 code?
What is the P0135 code?
The P0135 code is a diagnostic trouble code (DTC) that indicates a problem with your car’s engine’s oxygen sensor (also known as the O2 sensor) heater circuit.
Specifically, this code refers to Bank 1 Sensor 1, which is the first sensor in the exhaust system on the side of the engine with cylinder 1.
What does the oxygen sensor do?
The oxygen sensor is an important component of your car’s emissions control system. It measures the amount of oxygen in the exhaust gases and sends that information to the engine control module (ECM). The ECM uses this information to adjust the air/fuel ratio in the engine, ensuring that the engine runs efficiently and produces as few harmful emissions as possible.
Here are the top 7 symptoms you may experience if your car is displaying this code:
- Check Engine Light: One of the most common symptoms of a P0135 code is the illumination of the check engine light on the dashboard.
- Poor Fuel Economy: If your oxygen sensor is not functioning correctly, your car’s fuel economy can decrease due to an incorrect fuel-to-air ratio.
- Rough Idling: A faulty oxygen sensor can cause your car to idle roughly or stall out.
- Poor Performance: Your car may not accelerate or perform as well as it usually does, especially during acceleration or while climbing hills.
- Exhaust Smells: You may notice a strong odor of gasoline or sulfur coming from the exhaust system.
- Failed Emissions Test: If you’re required to take an emissions test, a P0135 code can cause your car to fail, preventing you from passing the test.
- High Emissions: A malfunctioning oxygen sensor can cause your car to produce higher emissions, leading to environmental damage and higher maintenance costs in the long run.
What causes the P0135 code?
The two most common causes of the P0135 code include the following:
- Failed oxygen sensor heater circuit: The most common cause of the P0135 code is a failed oxygen sensor heater circuit. This can be caused by a blown fuse, a faulty sensor, or a wiring problem.
- Bad sensor ground: If the ground connection for the oxygen sensor is faulty, it can cause the sensor to fail or malfunction.
How do you diagnose the P0135 code?
To diagnose the P0135 code, you’ll need a scan tool that can read DTCs. Here are the steps to follow:
- Use the scan tool to read the DTC and clear it.
- Start the engine and let it run until it reaches operating temperature.
- Use the scan tool to monitor the oxygen sensor’s voltage output. If the voltage output is not changing or is stuck at a certain value, it could be a sign that the sensor is faulty.
- Use a multimeter to check the resistance of the oxygen sensor’s heater circuit. If the resistance is outside of the manufacturer’s specified range, it could indicate a faulty sensor or wiring problem.
- Check the wiring for any signs of damage, such as frayed wires or broken connectors.
How do you fix the P0135 code?
If you’ve diagnosed the problem and determined that the oxygen sensor heater circuit is faulty, here are some steps you can take to fix the P0135 code:
- Replace the oxygen sensor: If the sensor itself is faulty, you must replace it. Be sure to use a sensor that is compatible with your car’s make and model.
- Check the wiring: If the wiring is damaged, you’ll need to repair or replace it.
- Replace the fuse: If the oxygen sensor heater circuit fuse has blown, you’ll need to replace it with a new one.
- Repair the ground connection: If the ground connection is faulty, you’ll need to repair or replace it.
The P0135 code indicates a problem with your car’s engine’s oxygen sensor heater circuit. It’s important to diagnose and fix this problem promptly to ensure that your car runs efficiently and produces as few harmful emissions as possible.
About the Author
This article was created with the assistance of AI technology to aid the author, John Cunningham, who is a seasoned Red Seal-certified auto technician with more than 25 years of experience in vehicle repairs. However, please note that John Cunningham has edited the content to ensure accuracy and quality.
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- How to use a fault code reader (video)
- Fault code reader I recommend for DIYers
- Fault code index page
- Beginner DIY maintenance page
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John Cunningham is an Automotive Technician and writer on Rustyautos.com. He’s been a mechanic for over twenty-five years and has worked for GM, Volvo, Volkswagen, Land Rover, and Jaguar dealerships.
John uses his know-how and experience to write fluff-free articles that help fellow gearheads with all aspects of vehicle ownership, including maintenance, repair, and troubleshooting.