Modern vehicles have an advanced monitoring system for most of its components. If there is a problem with a certain part, the driver will be notified, first through the warning light on the dashboard and then with an error code readable with an OBD-II scanner. If you all of a sudden get a check engine light, and you notice rough idling, grab a scan tool and check your car. These symptoms may point to a P0135 code error.
So, what does a P0135 code mean? The P0135 points to a problem with a heated oxygen sensor circuit. The engine has several oxygen sensors, and the P0135 refers to the sensor one on Bank 1. That sensor is located close to the first cylinder. The problem can be in the sensor, fuse, or wiring.
The usual diagnosis and fixing of this problem is relatively straightforward. But, there are cases where some not-so-common reasons may cause this issue. Stay with us, and learn all about the P0135 code and how to resolve it.
Understanding the P0135 OBD2 Code
To fully understand the P0135 code, we must explain the importance of an oxygen sensor in your car. This component is often overlooked because it is not on a list of parts that are often replaced. But, its function is essential for the work of the engine and the emission control system.
What Does P0135 Code Mean?
The O2 sensors have heating elements that help them achieve working temperature as fast as possible. That way the sensor work as short as possible in an open-loop operation. Sensors that work in an open loop cannot do their work properly, resulting in a rich fuel mixture.
When the P0135 trouble code is detected, that means the heater circuit is short or has measured excessive resistance levels.
Importance of the Oxygen Sensor
The oxygen sensor is installed in all cars made after 1980. They are located in the emission control system, and they measure the amount of oxygen in a gas or liquid. They compare those measured values with the levels of oxygen in the atmosphere. The sensor sends information to the engine control unit (ECU), to tweak the air-to-fuel ratio.
When the oxygen sensor is working properly, it helps in achieving the best fuel economy and engine performance. When the sensor is not working properly that results in poor fuel economy and overall rough work of the engine.
Sneaky Causes of the P0135 Code
The causes for the P0135 code are relatively straightforward, but there are cases where regular inspection doesn’t resolve the issue. Some problems are attributed to the bad O2 sensor, and others to different vehicle components.
- Problems with a power control module. If the PCM is in trouble, it can do wrong readouts, resulting in different error codes
- Failed emission test. If you fail the test, the O2 sensor needs to be one of the first components to inspect
- Faulty engine coolant temperature sensor. This can be a hidden cause for a P0135 code on rare occasions.
Pesky Symptoms of P0135 Code
There are other rare symptoms that can cause damage to the car and lower its performance:
- Faulty catalytic converter
- Exhaust leaks.
Sherlock Holmes-Style Diagnosis for P0135 Code
Diagnosing the P0135 code demands some electrical knowledge and tools. If you want to try a DIY operation, get an OBD-II scanner and a multimeter.
Using an OBD-II Scanner
For the preliminary diagnosis, you will need an OBD-II scanner.
- Check the system with a scanner for errors
- Delete the errors and go for a ride
- Wait and see what errors will come back.
Analyzing The Scan Data
Sometimes the P0135 code will come in pair with the error code P0155. That happens when the sensor on Bank 2 is also in trouble. If there are other error codes, you should also pay attention to them and find out why they are showing up.
Fixing Error Code P0135: Step-by-Step
The diagnostic and repair process should start with the most common issues that are easier to notice and repair. From there, move to less frequent causes of the error.
Step-by-step Repair Guide
- Check the wiring and the connectors. If you notice any problems or rust, replace the wiring. Test the fuse on the heater circuit
- Clear the errors and do a test drive. Wait and see will the code return
- Check the exhaust system. Sometimes cracks or holes can cause problems with the O2 sensor. If there are problems, contact the mechanic
- Inspect the engine ground. It has to be properly connected. If there is any corrosion, install the new ground
- Examine the O2 sensor voltage. For this, you will need a multimeter. Normal values are between 0.1 and 1 volt. If there are problems with the voltage, check for a blown fuse and faulty wiring
- Test the catalytic converter with a vacuum gauge. When the engine reaches optimum working temperature, the measured value should be around 18 Hg
- Check the catalytic converter for dirt. If it is dirty, clean it
If the error code remains, replace the oxygen sensor. If even that doesn’t resolve the problem, the cause can be somewhere else in the electrical system or in the PCM.
Check Out How to Fix P0135 Engine Code in 2 Minutes:
Replacing the Faulty Oxygen Sensor
Replacing the sensor is not too difficult if you have experience with a car mechanic.
- Park the car on a flat surface and raise it on the jacks
- Locate the sensor. The sensor is installed on the exhaust pipe going away from the motor to the back of the vehicle. It looks like a spark plug with a black cable coming out of it
- Unplug the connector’s wiring. Locate the small tab on the end of the plug. Push the plug down and pull it out
- Find a proper size spanner and unscrew the sensor. Usually, it is a 3/8-inch ratchet wrench fitted with a 7/8 socket. If the sensor is stuck spray it with penetrating oil
- Prepare the new sensor. Add the anti-seize gel to the sensor threads
- Turn the wrench clockwise to secure the sensor. Do not overtight it
- Connect the new sensor with an electrical connector.
Dealing with Wiring and Connector Problems
Wires and connectors are exposed to the elements, dirt, and debris. That can cause faster wear and even corrosion. Bad wiring and connectors will lead to problems with the sensor. The problem can be in open or high resistance values, or a short circuit somewhere in the sensor.
There is a way to fix bad wiring, but you need to have some electrical knowledge and experience. If you want to fix it, you will need to do a bit of rewiring. That can be a time-consuming job that you can leave to the mechanic. If a short circuit happens inside the sensor, the whole sensor needs to be replaced.
Preventive Measures
You cannot do much to prevent the problem with the oxygen sensor. Usually, the problem is in the wiring. You can do a visual check from time to time. Sometimes the wires can fall onto the hot exhaust parts. There they melt and they are badly grounded.
Tips for Avoiding Future Occurrences
Common issues that will cause the P0135 code are the faulty wire harness and problems with the fuse and the connectors. Check them regularly to avoid problems. Also, check that the wires are not in contact with anything that can cause a short circuit.
Regular Maintenance
Talk with your mechanic to inspect the sensor when the car is raised on the jack. The mechanic can also check the grounding of the engine. That way, you will minimize the chance of problems with the oxygen sensor.
FAQs
Can An Exhaust Leak Cause P0135?
Yes, an exhaust leak can cause the P0135. A leak will result in a faulty readout by the sensor.
Can You Drive with a P0135 Code?
Yes, you can drive with a P0135. But you will experience excessive fuel consumption, rough idling, and black exhaust gases. If you avoid resolving these issues, you are risking internal engine damage and increased labor costs.
Where is the Fuse for O2 Sensor?
It depends on the model of the car. Sometimes it is in the fuse box under the hood or the driver’s side dashboard. One way to identify it is by its rating. Depending on the car, the fuse for the oxygen sensor is rated between 15 and 30 amps.
How To Fix P0135 Code After Replacing O2 Sensor?
If replacing the O2 sensor didn’t resolve the P0135 code problem, there are other issues to address.
– Checking and fixing any problems with the wiring
– Checking the engine ground. If the ground is bad, replace it
– Check the exhaust for leaks. A bad exhaust will lead to problematic readouts of the sensor
– Inspect the catalytic converter. Clean it if it is clogged.
Need More Help with a P0135 Code?
Fixing a P0135 is usually a simple job. In most cases, all it takes is to fix the wiring or replace the sensor. The sensor costs between $200 and $300, and the wiring can be a bit pricier. But do not let this problem slide. It will grow over time, causing problems for the combustion process and the whole engine.
If you are not up to resolve this yourself, contact a mechanic. He will properly diagnose the issue, and you will not lose any sleep over this problem. Sometimes, the best thing is to let a professional do his job.
