What it means
The Bank 1 Sensor 4 oxygen sensor shows no expected signal activity. Sensor location and function vary with the exhaust system.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
How it works
Bank 1 Sensor 4 is the fourth oxygen sensor identified on the bank containing cylinder 1, with its location determined by the exhaust layout. This code sets when the module detects no expected signal activity from that sensor, which can result from a failed sensor, open wiring, a poor connection, or a heater or power-circuit problem.
Common causes
Most likely first.
- Oxygen sensor failure
- Open or damaged sensor wiring
- Loose or corroded connector
- Sensor heater or its power circuit fault
Symptoms
- Check engine light on
- Increased fuel consumption
- Possible rough idle or hesitation
- Failed emissions test
How to diagnose it
- Check freeze-frame data and Bank 1 Sensor 4 live data to confirm the signal is inactive and note whether the sensor was expected to be operating.
- Locate the sensor using service information and inspect its connector and harness for a disconnected plug, broken wire, heat damage, or corrosion.
- Check connector pins for a pushed-back terminal or poor contact, and check the relevant fuse if the design uses one.
- Test the signal wiring for continuity and check the sensor's power, ground, and heater circuit as applicable using the manufacturer's procedure.
- If the circuits and connections are intact, test Bank 1 Sensor 4 for failure.
Common fixes
- Reconnect and secure a loose Bank 1 Sensor 4 plug.
- Repair an open or heat-damaged wire in the sensor harness.
- Restore a failed power, ground, or heater-circuit connection affecting Bank 1 Sensor 4.
- Replace Bank 1 Sensor 4 if it produces no signal despite sound wiring and supply circuits.
Can I keep driving?
Driving a short distance is usually possible if the engine runs normally, but fuel use and emissions may increase. Avoid continued driving if it runs roughly or hesitates, and repair the fault before an emissions inspection.
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.