P0043
HO2S Heater Control Circuit Low Bank 1 Sensor 3
Oxygen sensor heater
Generic OBD-II
Medium
What it means
P0043 means the ECM detected low voltage in the heater circuit of the Bank 1, Sensor 3 oxygen sensor — a deep-downstream sensor. The internal heater brings the sensor to operating temperature quickly so it can read exhaust oxygen accurately. The car still drives fine, but the fault trips the check-engine light and blocks the emissions readiness monitor from completing.
Medium
Can I keep driving? Yes — the car drives normally, but the affected oxygen sensor warms up slowly, so expect a check-engine light and a likely emissions-test failure until it's fixed.
Common symptoms
What you'll notice
- Check-engine light on
- Failed or incomplete emissions test (readiness monitor won't set)
- Slightly reduced fuel efficiency
- Usually no change in how the car drives or feels
Common causes
Most likely first
- Failed oxygen sensor heater element (Bank 1, Sensor 3)Likely
- Short-to-ground or open in the heater control wiringCommon
- Corroded or loose connector at the sensorCommon
- Blown fuse feeding the heater circuitLess often
- Faulty ECM/PCM driver (rare — check wiring and sensor first)Less often
How to diagnose & fix
Work through it in order
- Read freeze-frame data and confirm the code is current, not a one-time glitch.
- Inspect the Bank 1 Sensor 3 connector and wiring for corrosion, chafing, or a loose pin.
- Check the heater fuse, then measure heater element resistance against spec.
- Verify power and ground reach the heater connector with the key on.
- If wiring, fuse, and power are good, replace the oxygen sensor. Clear and re-test.
FAQ
Quick answers
Is it safe to drive with P0043?+
Yes. This is a sensor-heater fault, not a running problem — the engine drives normally. Just fix it before an emissions test, since the readiness monitor won't complete.
Can I just clear P0043?+
It will clear, but it returns once the ECM re-tests the heater circuit. The underlying wiring or sensor fault has to be repaired for it to stay off.
Related codes
Often seen with P0043
Read & clear P0043 yourself
Scan your car, confirm the code, and clear it once it's fixed — with OBD DashX on your phone.
✓ Verified name — SAE J2012 / ISO 15031-6Guidance reviewed by OBD DashX