P1141

Code

BUICK P — Powertrain

HO2S Bank 1 Sensor 2 Average Voltage Level

Brand: BUICK

Type: P — Powertrain

Views: UK: 36 EN: 46 RU: 37

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Page language: EN

Faulty Bank 1 Sensor 2 oxygen sensor (contaminated, aged, or failed)
Damaged or corroded wiring or connector to the sensor (open, short to power/ground)
Exhaust leak upstream of the downstream sensor
Inefficient or damaged catalytic converter (bank 1)
Long-term fuel trim issues (rich or lean condition) affecting downstream readings
Heater circuit failure in the sensor

Check Engine MIL illuminated
Possible failed emissions test
No or minimal change in drivability in many cases (downstream sensor often not used for closed-loop fuel control)
Possible persistent long-term fuel trim anomalies
Reduced catalyst monitoring readiness

Read and record freeze frame and readiness status with a scan tool; note any related codes (upstream O2, fuel trims, catalyst codes)
Inspect sensor connector and wiring for damage, corrosion, or chafing; wiggle harness while monitoring for voltage changes
Visually inspect exhaust for leaks, especially near the manifold and catalytic converter
Compare live voltage traces of Bank 1 Sensor 1 (upstream) and Sensor 2 (downstream) with a scan tool
Measure heater circuit voltage and sensor heater resistance per manufacturer spec
Check long-term and short-term fuel trims for signs of lean or rich conditions

Downstream (B1S2) typical behavior: relatively stable voltage with small fluctuations; not the rapid switching of upstream sensor
Expected average voltage (typical): around 0.4–0.6 V when catalyst is healthy (manufacturer-specific thresholds apply)
Unhealthy readings: persistently low (~0.8 V) average or no variation over time
Heater resistance (typical for heated zirconia sensors): roughly 3–20 ohms (check vehicle spec)
Heater supply: battery voltage present at connector with PCM control to ground or switched feed as specified

Verify the DTC with a scan tool, record freeze frame and note any other stored codes (upstream O2, fuel trims, P0420, etc.).
Inspect sensor wiring and connector for damage, corrosion, loose pins, or water ingress. Repair or clean as needed.
Check for exhaust leaks upstream of the downstream sensor; repair any leaks before further testing.
Using a scan tool, monitor B1S1 (upstream) and B1S2 voltages simultaneously during warm idle and a defined drive cycle. Downstream should show a relatively steady voltage; if it mirrors upstream switching, the catalyst may be inefficient.
Measure sensor heater circuit resistance with the connector disconnected; compare to spec. Verify heater supply voltage and PCM switching with backprobe while engine running/warm-up.
Check short-term and long-term fuel trims and any related sensors (MAF, MAP, fuel pressure, injectors) for causes of abnormal air/fuel that could affect downstream voltages.
If wiring and heater are good and upstream sensor/engine are operating normally, evaluate catalytic converter efficiency (voltage correlation between upstream and downstream sensors, temperature, backpressure as applicable).
If suspicion remains on the sensor, replace Bank 1 Sensor 2 with a correct OEM or equivalent OE-quality sensor and clear codes. Re-test and perform a drive cycle to confirm the issue is resolved.
If the new sensor also reports abnormal average voltage, investigate PCM power/ground and consider professional PCM testing or replacement.

⚠️ Status

Bank 1 Sensor 2 oxygen sensor average voltage is out of expected range (HO2S B1S2 average voltage abnormal).

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 1.0-2.5 hours

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P1141 — HO2S Bank 1 Sensor 2 Average Voltage Level