Code
P22B6
Generic
P — Powertrain
O2 Sensor Pumping Current Trim Circuit Low Bank 1 Sensor 2
Views:
UK: 18
EN: 43
RU: 19
AI status
Completed
Completed
100%
Causes
- Faulty wideband/UEGO O2 sensor (Bank 1 Sensor 2)
- Open, shorted, or corroded wiring or connector at the sensor
- Poor ground or reference voltage to the sensor
- Contaminated or aged sensor (soot, silicone, coolant, oil)
- Exhaust leak upstream of the sensor affecting readings
- Heater circuit fault (if integral heater affects sensor operation)
Symptoms
- Malfunction Indicator Lamp (MIL) or check engine light on
- Emission test failure or elevated tailpipe emissions
- Possible stored downstream O2 sensor fault codes
- Rare or minor drivability effects (downstream sensor usually not used for closed-loop fueling)
- Possible poor catalyst efficiency code (e.g., P0420) if sensor cannot verify converter
What to check
- Read freeze-frame and live data with a capable scan tool supporting wideband pump current
- Visual inspection of the sensor, wiring harness, and connector for damage, corrosion, or heat damage
- Check for exhaust leaks upstream of the sensor flange or gasket area
- Measure heater circuit resistance and supply voltage (if sensor has heater)
- Back-probe sensor signal and ground to verify reference voltage and continuity to PCM
- Check for related codes (catalyst efficiency, other O2 sensor codes)
Signal parameters
- Pump current (mA or µA) — expected non-zero range depends on sensor/condition; consult manufacturer data
- Sensor voltage or lambda output (V or lambda) from wideband controller
- Heater resistance (ohms) and heater supply voltage (V)
- Reference voltage and ground continuity to PCM (V)
- Response to induced air/fuel change (pump current should change when AFR is intentionally altered)
Diagnostic algorithm
- Verify the code is current; record freeze frame and live data. Clear codes and retest to confirm repeatability.
- Perform a visual inspection: check sensor body, wiring, connector, and nearby exhaust for leaks or damage. Repair any obvious faults.
- Ensure vehicle safety: allow exhaust components to cool before touching sensors.
- Check connector pins for corrosion, pushed-out pins, or melted plastic. Repair or replace connector as needed.
- Measure heater circuit (if present): with sensor disconnected, measure resistance. Compare to specification; check for heater supply voltage with ignition on.
- Back-probe the pump current/signal and ground with a scan tool capable of reading pump current. Verify the pump current is lower than expected under conditions where a change is expected (e.g., while varying AFR).
- Check continuity and resistance of signal/ground/reference wires from sensor to PCM. Repair any opens/shorts.
- Introduce a controlled AFR change (safe method such as propane enrichment or temporary fuel change per shop procedure) and observe pump current response — a healthy sensor will show a corresponding change in pump current.
- If wiring and heater are good but pump current stays low, replace the downstream wideband O2 sensor (Bank 1 Sensor 2).
- If sensor replacement does not clear the condition, check for PCM faults or require manufacturer-level diagnostics; consider PCM reprogram/replace only after all sensor and wiring checks are completed.
Likely causes
- Sensor internal failure or contamination (most common)
- Connector corrosion or broken wire between sensor and PCM
- Low or missing sensor reference/ground from PCM
- Exhaust leak near the sensor altering sensor environment
- Heater open or intermittent causing sensor not to reach operating temp
Fault status
Status
O2 Sensor Pumping Current Trim Circuit Low — Bank 1 Sensor 2. Downstream wideband O2 sensor pump current is lower than expected, indicating sensor or circuit fault.
Repair difficulty: Medium
Diagnostic time: 0.5-2.0 hours
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