What it means
The ECM detects a generic fault on the intake air oxygen sensor signal circuit on bank 1. A drifted or sluggish lambda sensor lets the mixture run lean or rich without correction — fuel economy and emissions suffer immediately.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
How it works
The Bank 1 intake-air oxygen sensor provides the control module with an oxygen reading used to assess mixture conditions for that bank. This circuit code sets when the module detects a fault in the Bank 1 sensor signal circuit and cannot rely on the reading for normal mixture control.
Common causes
Most likely first.
- Intake air O2 sensor failed
- Wiring or connector fault
Symptoms
- Check engine light on
- Increased fuel consumption
- Possible rough idle or hesitation
- Failed emissions test
How to diagnose it
- Record freeze-frame data and compare Bank 1 sensor readings with other available mixture data to see whether the signal is absent, erratic, or implausible.
- Inspect the Bank 1 intake-air oxygen sensor connector and harness for damage, loose pins, contamination, or contact with hot or moving parts.
- Check for intake or exhaust leaks near the sensor that could make its reported oxygen level misleading.
- Use a scan tool to watch the Bank 1 sensor signal as operating conditions change and compare it with the manufacturer's expected response.
- Test the signal, reference, and ground circuits for opens, shorts, or poor connections according to the wiring diagram.
- If the wiring and related leaks check out, test or replace the Bank 1 intake-air oxygen sensor as indicated by the manufacturer's procedure.
Common fixes
- Reconnect or clean the Bank 1 sensor connector and secure the harness.
- Repair damaged signal, reference, or ground wiring to the Bank 1 sensor.
- Repair an intake or exhaust leak affecting the sensor reading.
- Replace the Bank 1 intake-air oxygen sensor if it fails response or circuit testing.
Can I keep driving?
Short local trips are generally possible if the engine runs smoothly, but avoid hard acceleration if it hesitates or runs roughly. Continued driving with inaccurate Bank 1 mixture feedback can increase fuel use and emissions and may damage the catalytic converter.
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.