What the OBD-II code p0135 means

Fault code P0135 – a step-by-step guide to diagnosing and fixing it

The meaning of error code P0135 – Oxygen Sensor Heater Circuit Malfunction (Bank 1, Sensor 1)
P0135
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P0135: causes, symptoms and repairs

The meaning of fault code P0135

The P0135 code is triggered when there is a problem with the oxygen sensor heater circuit on cylinder bank 1. It appears after the engine control module has detected a short circuit or high resistance in the component's circuit. If the sensor doesn’t reach a certain temperature, it will not function properly. The longer it takes to warm up, the more difficult it will be for the engine to achieve the optimum operating conditions.

Common causes

  • Damaged cables or wires, obstructing the power supply network. The insulation sheath of the wires can fray or melt, resulting in a short circuit.
  • A blown sensor fuse, caused by a power surge
  • A faulty engine coolant temperature sensor
  • A powertrain control module malfunction, although this is less common
Symptoms of code P0135

  • The engine runs rough, particularly while warming up
  • The check engine comes on, indicating that there’s a problem
  • The vehicle is less fuel efficient
  • There’s change of smell and the exhaust system sounds strange
Recommended repairs

  • To make sure that this isn’t a false error, you can reset the DTCs using an ODB2 scan tool. Take the car for a quick test drive to determine whether the fault is still there. If the check engine light comes on again, you will need to identify the underlying causes.
  • Inspect the housing of the oxygen sensor and look for signs of contamination or damage. To do this, you will need to remove the device. It is possible to clean it using a specialised cleaning agent for air flow sensor. It may also be necessary to remove deposits and grime from the electrical connector pins around the device.
  • You can visually inspect the wires and power supply cable for mechanical or thermal damage, however, it is advisable to check the voltage, even if the parts seem to be in a good condition. You can do this using a multimeter. If it doesn’t detect a voltage, you should check that this isn’t due to a blown fuse. The wires should always be examined first before the lambda device is replaced.
  • You can also use the multimeter to test the resistance of the heater circuit. Compare the readings with the standard values specified by the manufacturer.
  • Any defective components should be replaced. You may also want to check whether the engine coolant sensor is functioning properly.
Frequently Asked Questions (FAQ)

What does the P0135 code mean?


It means that a short or open circuit has been detected in the car lambda sensor heater on cylinder bank 1.

What causes the error?


It is typically caused by a sensor malfunction, a blown fuse, oxidation, or faulty wires.

Can I still drive my car or is it too serious?


Driving is advised against because this malfunction will affect the fuel mixing process. If the mixture contains too much fuel, it will continue to burn outside of the combustion chambers, increasing the risk of thermal damage to the catalytic converter and exhaust system.

How much will it cost to fix?


This will depend on the repair methods required and which parts are replaced. Replacing the sensor is fairly straightforward and it can take as little as 10 minutes. The labour costs should therefore be relatively low. You can prevent short circuits or wire damage from reappearing by checking the wires regularly, making sure that they don’t overlap or touch anything that could damage them or cause an interference.

The meaning of fault code P0135 is: Oxygen Sensor Heater Circuit Malfunction (Bank 1, Sensor 1). Find out what exactly this means, the symptoms and causes of the code P0135 and how to fix the malfunction.
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