Oxygen (lambda) sensors

P0135 Front oxygen sensor heater not working

By: Diagno editorial team · Updated: 2026-10-15

P0135 means: Front oxygen sensor heater not working. The oxygen (lambda) sensor has a built-in heater so it warms up quickly. OK to drive, but have it checked soon. The repair usually costs about €60–250 in Estonia. The most common cause: sensor heater element has failed (most common).

Is it safe to drive?OK to driveOK to drive, but have it checked soon.

Typical repair cost€60–250parts and labour in Estonia

What it means

The oxygen (lambda) sensor has a built-in heater so it warms up quickly. If the heater fails, the sensor doesn't work while the engine is cold and fuel consumption may go up.

What could be wrong

1Sensor heater element has failed (most common)
2Fuse has blown
3Wire or connector is melted or broken

What you can check yourself

Check the lambda heater fuse in the fuse box. Make sure the sensor wire isn't touching the hot exhaust pipe. You can do the simpler checks yourself.

How we fix it

We measure the heater resistance and power supply
We replace the fuse or repair the wire
We replace the oxygen sensor

Standard SAE description: O2 Sensor Heater Circuit Malfunction (Bank 1 Sensor 1)

Want a definite answer?

Bring the car to our workshop in Estonia for diagnostics. We read the fault codes, test the sensors and tell you what is wrong. Repair price depends on the work involved, generally €45 per hour.

Book a diagnostic check

Questions

What does fault code P0135 mean?

Front oxygen sensor heater not working. The oxygen (lambda) sensor has a built-in heater so it warms up quickly. If the heater fails, the sensor doesn't work while the engine is cold and fuel consumption may go up.

Can I drive with code P0135?

OK to drive, but have it checked soon.

How much does it cost to fix P0135?

Roughly €60–250 in Estonia. The price depends on exactly what has failed and on the car.

How is P0135 fixed?

We measure the heater resistance and power supply. We replace the fuse or repair the wire. We replace the oxygen sensor.

Based on AI combined with our hands-on workshop experience and knowledge. This information is general and prices are approximate (Estonian workshop rates). The same code can mean different things on different cars. Only an inspection of the car gives a definite answer.