P2243Powertrain
Powertrain · SAE
Wideband O2 Sensor B1S1 — Reference Voltage Circuit Open
Meaning
The ECU detects an open circuit on the reference voltage (Vref) line of the upstream wideband sensor, bank 1. The sensor cannot generate a stable Nernst signal and AFR measurement is compromised.
Common causes
- Broken Vref wire or corroded connector
- Failed wideband O2 sensor (internal Vref open circuit)
- Short to ground or to power in the Vref wiring
- ECU Vref supply out of tolerance or absent
- Damaged or loose Vref pin at the ECU connector
Symptoms
- Malfunction indicator lamp (MIL) on
- Incorrect or absent AFR signal in diagnostics
- Open-loop operation
- Increased fuel consumption
- Elevated emissions
Severity
High: without reference voltage the sensor cannot correctly measure the air/fuel ratio, negatively affecting emissions and the catalytic converter.
What to do
- Inspect the B1S1 sensor connector and Vref wiring for breaks, corrosion, and shorts
- Measure Vref voltage at the sensor connector with ignition on (typical value 2.5 V or as specified by the manufacturer)
- Check wiring continuity between sensor connector and ECU pin
- Replace the wideband O2 sensor if wiring is intact
- If the fault persists, check the ECU Vref output