How can I fix code P0135?

Alton Alexander
By Alton AlexanderUpdated on June 4th, 2022

P0135 is an error code that typically indicates a problem with the oxygen sensor heater circuit in sensor 1. This error code can be caused by a variety of factors, including a blown fuse, a faulty oxygen sensor, or a problem with the oxygen sensor heater circuit. In some cases, the error code may also be caused by a problem with the engine control module (ECM).

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1. Check the oxygen sensor and wiring harness

  1. Disconnect the negative battery cable.
  2. Remove the airbag cover.
  3. Locate the oxygen sensor.
  4. Disconnect the sensor connector.
  5. Remove the oxygen sensor.
  6. Inspect the sensor for damage or debris.
  7. Clean the sensor and connector.
  8. Reconnect the sensor connector.
  9. Reconnect the negative battery cable.
  10. Replace the airbag cover.

2. Check for leaks in the exhaust system

  1. Remove the engine cover.
  2. Inspect the exhaust system for any leaks.
  3. If there are any leaks, repair them using the appropriate sealant.
  4. Replace the engine cover.

3. Check the air filter

  1. Remove the air filter.
  2. Inspect the filter for debris, cracks, or other damage.
  3. Replace the filter if necessary.
  4. Reconnect the air intake tube.
  5. Start the car and check for the P0135 code.

4. Check the fuel injectors

  1. Remove the fuel injectors as a whole by unscrewing the bolts that hold them in place.
  2. Inspect the inside of each injector for any deposits or damage. If there is anything wrong with the injector, replace it.
  3. Reconnect the fuel injectors to the fuel rail and check that they are seating properly. If they are not, adjust them until they are.
  4. Reconnect the fuel lines and check for leaks. If there are any, fix them.
  5. Start the engine and run it for a few minutes to ensure that the injectors are working correctly.

5. Check the ignition system

The first step would be to check the fuel system. If there is no fuel flow, the problem could be with the injectors, the pump, or the fuel rail. Next, check the spark plugs and wires. If there is no spark, the problem could be with the coil, plug, or spark plug gap. Finally, check the ground circuit.

6. Check the computer for codes

  1. Check the fuel system for leaks. This could be caused by a defective fuel pump, a clogged filter, or a broken fuel line.
  2. Check the airbag sensor for proper operation. If the sensor is not working, the airbag may not deploy in a crash.
  3. Check the engine for misfires and over-heating. A weak or faulty engine could be the cause of the code.
  4. Check the exhaust system for leaks. A broken or clogged catalytic converter could cause this problem.
  5. Check the ignition system for problems. A faulty spark plug could be the culprit.

If you didn't find success with an option above, then try:

  1. Check the emissions system