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If your scan tool shows a stored P0147 code, this article should help you figure out where to start. Some engines will have two upstream sensors (one for each bank) and only one downstream sensor (where there’s a single light-off catalyst serving both banks). That third sensor is the focus of this particular code.

What Does the P0147 Code Mean?

Diagnostic trouble code (DTC) P0147 stands for “O2 Sensor Heater Circuit Bank 1, Sensor 3.” It is set when the powertrain control module (PCM) perceives the oxygen sensors to be taking longer than usual to reach operating temperatures. The code may also be logged if the PCM detects a potential problem with the oxygen sensor heater or its circuit.

a car's oxygen sensor
Code P0147 may be set if the PCM perceives the oxygen sensors to be taking longer than usual to reach operating temperatures.

“Bank 1” refers to the side of the engine that contains cylinder #1. “Sensor 3” refers to the downstream oxygen sensor located at the rear of the catalytic converter.

The oxygen sensor needs to be at a high temperature to produce a voltage. It uses a heater to swiftly reach the right operating temperature and maintain this condition during idle. As the sensor reaches the optimal temperature, the PCM monitors the voltage as well as the signal voltage for closed-loop fuel control.

During regular closed-loop fuel control operation, the PCM will add fuel to enrich the mixture when the oxygen sensor detects a lean condition in the exhaust. The PCM will reduce fuel or “lean-out” the mixture when the sensor detects a rich exhaust condition. The downstream oxygen sensor may also be used to monitor the efficiency of the catalytic converter.

The oxygen content of the exhaust indicates whether the engine has gone lean or rich. When the oxygen sensor detects that the engine is running rich, the signal voltage is high. If the engine is lean, the signal voltage decreases.

This fluctuation of predetermined voltage is sometimes referred to as activity or switching. It can be monitored with the oxygen sensor signal voltage.

The PCM determines if the oxygen sensor heater or its circuit is functioning properly. The P0147 code is logged when the PCM detects an issue with the performance of the oxygen sensor heater.

You can find more information that can help you execute proper DIY diagnosis and troubleshooting of P0147 in our technical discussion about the heating process of oxygen sensors.

Note: The definition of code P0147 may be different depending on the vehicle manufacturer. Consult the appropriate repair manual or repair database for the exact code definition.

What are the Possible Causes of the P0147 Code?

P0147 is a generic code, so it can have several triggers. Here are the most common:

What are the Common Symptoms of the P0147 Code?

You may notice the following symptoms if you drive a vehicle with a logged P0147:

bad oxygen sensor
A faulty oxygen sensor can trigger code P0147.

How to Diagnose the P0147 Code

For a quick and fairly easy DIY test for P0147, if you have an old O2 sensor that fits your vehicle, you can cut the wires off the sensor and connect a tail light bulb to the heater wires; those will be two of the four wires that are the same color. They’ll be a different color from the other two wires, which are signal and signal ground for the sensor.

Once you’ve created that tool, you can connect it to the wire harness so that if the heater is receiving voltage from the ECM/PCM, the bulb will light. Typically, the heater will begin to receive voltage as soon as the key is turned to the “on” position, even before the engine is started.

If you don’t see the light illuminate, you’ll need to check fuses and circuits visually to see what you can see. But don’t replace the ECM/PCM for this; usually, it’s wiring or connectors. But if the light does illuminate, remove the O2 sensor and check the resistance of the heater. It should be around 6 ohms or so. The heaters do fail open sometimes and that’s the most common cause of this code.

Take note that to avoid the possibility of engine damage, code P0147 should be resolved immediately. However, it may be difficult to diagnose this code because there are many possible triggers associated with it.

Keep in mind that the diagnostic and repair steps for this code should depend on the specifications of your vehicle. As all cars are built differently, they may require vehicle-specific diagnostic processes. Always refer to a repair manual before attempting anything.

If you’re still unsure of how to proceed after reading the repair manual, it might be best to leave the diagnosis to a technician.

How to Fix the P0147 Code

Code P0147 may be set in vehicles of varying makes and models. Therefore, you should refer to the factory repair information specific to your vehicle before DIY-ing any repairs. If you aren’t confident in your auto repair skills, it may be best to leave the job to a professional.

However, if you’re set on resolving this code on your own, make sure your automotive knowledge is up to date. Refer to a repair manual or an online repair database to learn how to resolve code P0147.

Any information provided on this Website is for informational purposes only and is not intended to replace consultation with a professional mechanic. The accuracy and timeliness of the information may change from the time of publication.

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