P2240Powertrain
Powertrain · SAE
Wideband O2 Sensor B2S1 — Pumping Current Circuit Open
Meaning
The ECU detects an open circuit on the pumping-current line of the upstream wideband (AFR) sensor, bank 2. Closed-loop air/fuel ratio control for bank 2 is not available.
Common causes
- Broken pumping-current wire or corroded connector on bank 2 side
- Failed wideband O2 sensor bank 2 (internal open circuit)
- Short to ground in wiring between ECU and B2S1
- Faulty sensor control module (IPCU)
- Damaged ECU driver output for bank 2
Symptoms
- Malfunction indicator lamp (MIL) on
- Open-loop operation on bank 2
- Increased fuel consumption
- High exhaust emissions (CO, HC)
- Possible bank imbalance on V or flat engines
Severity
High: without the AFR signal for bank 2, mixture control is not possible, risking damage to the bank 2 catalytic converter.
What to do
- Inspect the B2S1 sensor connector and wiring for mechanical damage, 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 B2S1 if wiring is intact
- If the fault persists, inspect the ECU driver output for bank 2