What it means
The ECU detects an electrical fault in the heater circuit of the third O2 sensor on bank 1. Heater current out of range, indicating open/shorted heater element, blown fuse or wiring fault.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
How it works
Bank 1 Sensor 3 is the third oxygen sensor in the bank 1 exhaust path where fitted, and its heater helps it reach operating temperature after startup. P0147 sets when the module detects abnormal heater-circuit current, which can come from an open or shorted heater, a fuse, or wiring.
Common causes
Most likely first.
- Heater element open
- Heater fuse blown
Symptoms
- Check engine light on after several drive cycles
- Slightly increased fuel consumption during cold start
- Delayed entry into closed-loop fuel control
- Failed emissions inspection (lambda readiness)
How to diagnose it
- Confirm P0147 with a scan tool, save freeze-frame data, and note whether it returns during a cold-start heater check.
- Locate Bank 1 Sensor 3 from service information and inspect its heater wiring and connector for heat damage, corrosion, or chafing.
- Check the relevant heater fuse and power supply before replacing the sensor.
- Test the Sensor 3 heater element and its wiring for an open or short using the manufacturer's specified method.
- If the heater and wiring test correctly, check the heater control circuit at the module according to service information.
Common fixes
- Repair damaged Bank 1 Sensor 3 heater wiring or connector pins.
- Replace the blown fuse after finding and correcting the cause.
- Replace Bank 1 Sensor 3 if its heater element fails testing.
- Repair a confirmed heater-control circuit fault.
Can I keep driving?
The car is usually drivable if it runs normally, but cold-start emissions monitoring may be delayed and an emissions inspection may fail. Get it diagnosed soon if other engine symptoms or codes appear.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.