What it means
The Bank 1 Sensor 4 oxygen sensor signal is biased or stuck rich. 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 an oxygen sensor at the fourth designated sensor position on Bank 1; its location and function vary with the exhaust system. The control module monitors its signal and sets P01F7 when the reading stays rich or is biased rich under conditions where the signal should respond differently.
Common causes
Most likely first.
- Oxygen sensor failure or contamination
- Damaged wiring or poor connector contact
- Engine running rich from a fuel or air metering issue
- Fuel pressure or injector problem
Symptoms
- Check engine light on
- Increased fuel consumption
- Possible rough idle or hesitation
- Failed emissions test
How to diagnose it
- Use a scan tool to save freeze-frame data and compare Bank 1 Sensor 4 live data with the other oxygen sensors.
- Inspect the Sensor 4 connector and wiring for loose or corroded terminals, heat damage, or chafing that could distort the signal.
- Check the sensor and its signal circuit, power, and ground against the manufacturer's specification.
- If the circuit is sound, look for evidence of a genuinely rich condition, such as abnormal fuel trims or other stored fuel-system codes.
- Check fuel pressure and injector operation using the manufacturer's procedures if scan data points to excess fuel delivery.
Common fixes
- Secure or repair a loose, corroded, or damaged Sensor 4 connection or harness.
- Correct an air-metering fault that is making the engine run rich.
- Repair a fuel pressure problem or leaking injector identified by testing.
- Replace Bank 1 Sensor 4 if its signal remains rich-biased after wiring and mixture faults are ruled out.
Can I keep driving?
A short, gentle trip is generally possible if the engine runs normally, but the rich reading can increase fuel use and emissions and may damage exhaust after-treatment if the engine is truly running rich. Stop driving if rough running or power loss becomes severe.
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.