Error Code P0147: O2 Sensor Heater Circuit Malfunction (Bank 1 Sensor 3)

Error Code P0147 is defined as Oxygen Sensor Heater Circuit Malfunction Bank 1, Sensor 3. This indicates the PCM (powertrain control module, or also known as ECM or engine control module in some makes) tested the O2 (oxygen) sensor heater circuit at startup and determined a problem in Bank 1, Sensor 3 of the heater circuit. This usually happens when the current amperage in the rear heater circuit is out of its normal range.

This code is a generic code, meaning, it applies to all makes and models of vehicles equipped with OBD-II and made since 1996 up to present. Details on specifications of the trouble code and troubleshooting may vary from one make and model to another.

Definition

The Oxygen sensor contains a heating element which allows it to reach the optimum operating temperature quickly. It allows engine to reach closed loop faster and stay in closed loop at idle, which ultimately lowers the emission. This circuit is supplied with a 12V battery feed from either the PCM or ignition circuit (depending on the model of the vehicle) and a ground. The PCM monitors the time it takes for the sensor to become active after the engine starts. If it takes too long for the Oxygen sensor to reach the optimal operating temperature, then it will activate the Error Code P0147.

Common Symptoms

Error Code P0147 can be quite tricky, as it doesn’t cause the engine to run differently. This is because the oxygen sensor is simply used for catalyst efficiency, not for fuel control. It will of course, activate the Check Engine light, and in some cases, it may show poor rough idle.

Possible Causes

The most common cause of Error Code P0147 is the heater circuit at startup has excessive current draw, opens or shorts. Meaning, for this error code, the PCM detects short, open or excessive current draw in the oxygen sensor bank 1, sensor 3 of the heater circuit. The most common causes would be:

  • Bad oxygen sensor heater circuit
  • Bad oxygen sensor, defective rear most O2 sensor
  • Connections or wiring harness problem

How to Check

Mechanics diagnose this error code by scanning the PCM for codes and document the freeze frame data.

Then, they will rerun the oxygen sensor to find out if it fails again. If it does fail, mechanics usually performs the pinpoint test for the sensor.

They will test the power and ground connector end of oxygen sensor heater circuit. Measure the resistance of the O2 sensor heater circuit and replace the sensor if it’s the faulty one.

They will also check the sensor wirings and look for signs of faulty ones.

Lastly, they will clear and retest the systems for faults.

How to Fix

Repairs for this error code are pretty simple and straightforward. If diagnosis shows it’s the sensor at Bank 1 Sensor 3 that is at fault, then it should be replaced.

Wiring and connectors to the Oxygen sensor bank 1 sensor 3 should be repaired, if not replaced.

In some cases, the fuse to the heater circuit of the O2 sensor heater circuit must be replaced.

This code may cause the vehicle to fail on emission testing as Check Engine light is triggered, and catalyst monitor will not pass the test.

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