Engine fault code P0135: What you should do now

What causes fault code P0135?

Cars are complex. Fault code P0135 can have a wide range of possible causes, such as:

• the lambda sensor is faulty.
• the lambda sensor’s heating element has a short circuit or a faulty fuse.
• the lambda sensor’s heating element has excessive resistance.
• the electrical connection is poor.
• damage or corrosion to the connections of the pre-catalytic lambda sensor
• faulty pre-catalytic lambda sensor
• faulty coolant temperature sensor.
• The battery charge is too low.
• Your vehicle has the wrong pre-cat lambda sensor.
• The electronic control unit is faulty.

How does error code P0135 manifest itself and how can it be rectified?

The various causes mentioned above manifest themselves in different ways. You may notice it immediately via the engine warning light coming on in the cockpit or the error code being shown on the display. In addition, for example, fuel consumption may increase and the vehicle’s engine may run roughly. What you can do now:

• The lambda sensor circuit should be repaired if the resistance is too high or there is a short circuit. You should also check the relevant connections. Sometimes water can cause the heating element to fail. If a fault is found, replace the relevant parts.
• Check the voltage with a multimeter to see if the battery is supplying power.
• Check for corrosion around the lambda sensor, including, for example, the engine’s earth connection.
• If none of the above helps: replace the lambda sensor. Depending on the fault, the lambda sensor may not be repairable and will need to be replaced entirely. Depending on the vehicle, the sensor is available from 30 euros.
• If none of these steps have helped to resolve error code P0135, take your car to a garage you trust. The electronic control unit should be examined there.