P0044 — HO2S Heater Control Circuit High (Bank 1 Sensor 3)

What P0044 means

The engine control module switches a heater inside the oxygen sensor so it reaches operating temperature quickly and reads exhaust gas accurately. P0044 sets when the control circuit for the heater of sensor 3 on bank 1, usually located after the main or second catalytic converter, shows higher voltage than expected. Typical causes are a failed heater element in the sensor, a wire shorted to voltage, or a faulty driver inside the control module.

Symptoms

• Check engine light on
• Slightly higher fuel consumption in some cases
• Occasional unstable idle
• Often no noticeable change in driveability
• Failed emissions or readiness test

Possible causes

1. Failed heater element in the bank 1 sensor 3 oxygen sensor
2. Heater control wire shorted to positive voltage
3. Corroded, damaged or loose sensor connector
4. Open circuit or poor connection in the wiring harness
5. Faulty heater driver inside the engine control module

How to diagnose

1. Scan for codes, note the freeze frame data, clear the code and see if it returns.
2. Inspect the harness and connector at bank 1 sensor 3 for chafing, heat damage, corrosion and moisture.
3. Confirm from a diagram which sensor is B1S3 on your vehicle so you test the right one.
4. Measure the sensor heater resistance with a multimeter and compare it to the service specification.
5. Check power supply and control signal at the connector with the ignition on.
6. Unplug the sensor and test the control wire for a short to voltage.
7. Look over the exhaust near the sensor for leaks or damage.
8. If the sensor and wiring are good, check the control module and its power and ground circuits.

Common fixes

• Replace the bank 1 sensor 3 oxygen sensor
• Repair the shorted wire or replace the damaged harness section
• Clean or replace the sensor connector
• Repair or replace the control module if its heater driver has failed

Questions and answers

Can I drive with a P0044 code?

Usually yes, for a short time. It doesn't normally harm the engine, but fix it soon so other faults don't go unnoticed.

What does B1S3 mean in P0044?

It is the third oxygen sensor on bank 1, the side of the engine with cylinder 1. It sits farther downstream in the exhaust, after a catalytic converter.

Do I always need a new sensor for P0044?

No. Check the wiring, connector and heater circuit power first. Replace the sensor if its heater resistance is out of spec and the wiring is good.

This is general information about the code. The meaning can differ between makes and models: a scan tool and the repair manual for your car will show the exact cause.