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P0134 OBD-II Trouble Code: O2 Sensor Circuit No Activity Detected (Bank 1 Sensor 1)

check engine light

P0134 code definition

The P0134 diagnostic trouble code is an indication that there is a problem with the oxygen sensor that is positioned before the catalytic converter and on the engine bank that houses cylinder #1.

What the P0134 code means

The oxygen sensor reads the amount of oxygen and fuel that comes through the exhaust to make sure the oxygen to fuel ratio is correct. The oxygen sensor sends that information to the power control module (PCM).

If there is an insufficient amount of oxygen in the exhaust, the power control module (PCM) will decrease the amount of fuel that is being used by the motor. This is important because if there is an insufficient amount of oxygen in the exhaust, the car will use more fuel and emit carbon monoxide into the air.

If there is an insufficient amount of fuel going into the exhaust, the power control module (PCM) will increase the amount of fuel that is being used by the motor. This is important because if there is an insufficient amount of fuel in the exhaust, the car will emit hydrocarbons and nitrogen oxides into the air.

What causes the P0134 code?

A properly working oxygen sensor millivolt reading moves up and down. When the power control module (PCM) detects that the oxygen sensor millivolt at a standstill, and not functioning properly, this will cause the P0134 trouble code. This trouble code can be caused by the following:

  • Faulty heater circuit
  • A wire that is broken or disconnected from the oxygen sensor
  • Corrosion in the connectors
  • Engine vacuum leak
  • A faulty power control module (PCM)

What are the symptoms of the P0134 code?

There are several things that you may experience in correlation with the P0134 trouble code:

  • The Check Engine Light on the dashboard may come on and the engine may stall.

  • You may experience the feeling that your car is running rough or that it is idling poorly.

  • You may also smell something similar to rotten eggs and/or see black smoke billowing from the exhaust.

  • There are times when a driver will not notice any of these symptoms, other than the Check Engine Light being on, but this is a rare occurrence.

How does a mechanic diagnose the P0134 code?

A technician will use an OBD-II scanner to diagnose the P0134 code. The freeze frame data should be captured in order to determine when the code was first set. At this point, the code should be reset and the vehicle test driven.

While test driving, the vehicle needs to reach normal operating temperature in order to see if the code comes back. If the fault code does come back, the wiring that goes to the oxygen sensor and grounds needs to be inspected. While inspecting the technician will look for breaks and corrosion. Live data should be observed in an effort to determine whether the millivolt valves are going low to high.

The oxygen sensor should also be inspected in order to determine whether it has power going to it and that it is receiving the proper signal voltage from the Power Control Module (PCM).

Common mistakes when diagnosing the P0134 code

A mistake that is commonly made when diagnosing the P0134 trouble code is the assumption that the oxygen sensor is the first thing that needs to be replaced without considering other possibilities.

Sometimes the oxygen sensor itself, is not the problem and there are other things that could prevent the oxygen sensor from working, such as the wiring to the oxygen sensor. The wiring should be inspected and ruled out as the cause before replacing the oxygen sensor.

How serious is the P0134 code?

It is not likely that the P0134 trouble code will prevent operation of the vehicle, in that it should start and run, but drivers may experience a lack of power.

Driving with a P0134 trouble code could cause damage to the catalytic converter but it would take an extended period of time to do so. What is most impactful with this trouble code is that it is common for there to be a decrease in fuel economy so the car will burn fuel at a higher rate of speed. For this reason, it is important to have a technician complete a diagnosis of the code, as well as making the necessary repair, as soon as possible.

What repairs can fix the P0134 code?

  • The technician should use a scanner to validate the fault code. After the fault code has been validated, it should be reset and a test drive should be performed. If the Check Engine Light returns with the same fault code, an inspection should follow.

  • The wires and connectors should be inspected for any damage. If the wires and connectors are damaged, they should be repaired or replaced. Reset fault code and test drive.

  • If the Check Engine Light comes on again and the technician gets the same code, the oxygen sensor will need to be replaced.

  • If the P0134 trouble code comes back after replacing the oxygen sensor, the exhaust pipe and heater fuse should be inspected to rule out possible damage of the two.

Additional comments for consideration regarding the P0134 code

Most commonly, the oxygen sensor itself will need to be replaced with a new one. However, before replacing the oxygen sensor, a problem with the wires and connectors should be ruled out.

It is important to reset the fault code and test drive the vehicle after repairing or replacing the wires, connectors, or oxygen sensor to see if the code comes back, before moving on to the next possible problem.

If the fault code still comes back after inspecting the wiring and/or connector(s) and replacing the oxygen sensor there are some less likely possibilities for getting this code. Some cars have a fuse for the oxygen sensor heater circuit and in this case, it is possible that the fuse has blown, although this is not common.

It is also possible that the exhaust pipe could have holes or excessive rusting. The last and least likely possibility for getting this code is that the power control module (PCM) is faulty and needs to be replaced.

Need help with a P0134 code?

YourMechanic offers certified mechanics who will come to your home or office to diagnose and repair your vehicle. Get a quote and book an appointment online or speak to a service advisor at 1-800-701-6230.

The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details
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