P2237Powertrain
Powertrain · SAE
Wideband O2 Sensor B1S1 — Pumping Current Circuit Open
Meaning
The ECU detects an open circuit on the pumping-current line of the upstream wideband (AFR) sensor, bank 1. Closed-loop air/fuel ratio control is not possible.
Common causes
- Broken pumping-current wire or corroded connector
- Failed wideband O2 sensor (internal open circuit)
- Short to ground in wiring between ECU and sensor
- Faulty sensor control module (IPCU)
- Damaged ECU driver output
Symptoms
- Malfunction indicator lamp (MIL) on
- Open-loop operation, incorrect mixture
- Increased fuel consumption
- High exhaust emissions (CO, HC)
- Possible power loss
Severity
High: without sensor signal, mixture control is not possible, risking catalytic converter damage and elevated emissions.
What to do
- Visually inspect the B1S1 sensor connector and wiring for breaks, corrosion, or shorts to ground
- Measure resistance of the pumping-current circuit from connector to ECU (should be < 1 Ω)
- Check sensor heater supply voltage
- Replace the wideband O2 sensor if wiring is intact
- If the fault persists after replacement, inspect the ECU driver output