Code
P0157
LAND ROVER
P — Powertrain
low circuit voltage of the sensor P215 (bank 2 sensor 2)
Views:
UK: 21
EN: 29
RU: 34
AI status
Completed
Completed
100%
Causes
- Faulty bank 2 sensor 2 (downstream O2 sensor)
- Shorted signal wire to ground
- Open/poor connector or corroded terminals at the sensor
- Heater circuit failure (open/short) in the sensor
- Exhaust leak upstream of the sensor
- Failed catalytic converter affecting downstream sensor output
Symptoms
- Check Engine Light (MIL) illuminated
- Reduced fuel economy
- Possible failed emissions test
- Rough idle or hesitation (if related to broader sensor/heater failure)
- Stored freeze-frame data showing low O2 voltage on B2S2
What to check
- Read freeze-frame and monitor live data for bank 2 sensor 2 voltage and heater status
- Visual inspection of sensor, connector, and harness for damage, corrosion, or exhaust soot
- Backprobe sensor signal with a multimeter or scan tool while engine is at operating temperature
- Measure heater circuit resistance and check for battery voltage at heater connector with key on
- Check for continuity and shorts between signal wire and ground or battery
- Inspect for exhaust leaks upstream of the downstream sensor and around the catalytic converter
Signal parameters
- Typical oxygen sensor signal range (zirconia narrowband): ~0.1 V (lean) to ~0.9 V (rich)
- Downstream (post-cat) sensors often show less switching; expected steady-ish voltage ~0.4–0.6 V when catalyst is working
- Low-voltage fault threshold commonly below ~0.1 V (vehicle-specific)
- Heater circuit resistance (typical range): ~2–20 ohms depending on sensor — consult vehicle spec
- Heater supply: battery voltage present at heater feed with engine off and key ON (relay/fuse dependent)
- PCM reference and ground must be within normal battery and ground voltage ranges
Diagnostic algorithm
- Retrieve and record freeze-frame data, pending/related codes, and battery voltage.
- Perform a visual inspection of Bank 2 Sensor 2 harness and connector for damage, corrosion, water intrusion or soot.
- With engine warmed up, monitor B2S2 voltage with a scan tool. Note if voltage is stuck low (
- Backprobe the sensor signal wire and confirm low voltage at the harness. Compare to sensor body ground and PCM ground.
- Inspect/verify PCM ground(s) for integrity on bank 2 circuits.
- Test heater circuit: with key off, measure resistance across heater terminals and compare to spec; with key ON, check for battery voltage on heater feed and proper switching when engine starts.
- Check wiring continuity from sensor signal to PCM and for short to ground or battery using an ohmmeter; repair any short/open found.
- If wiring and heater are good, if possible swap with the other bank’s downstream sensor (if same part) to see if code follows the sensor (only if identical and swapping is safe for diagnosis).
- If sensor behaves correctly when swapped or wiring checks out, replace the sensor and clear codes. Re-run diagnostics and verify proper operation of B2S2 live data.
- If low voltage persists after sensor replacement, investigate PCM outputs/inputs and catalytic converter condition (efficiency) as a root cause.
Likely causes
- Damaged/shorted sensor signal wire or corroded connector
- Failed downstream O2 sensor
- Heater element open or wiring fault preventing proper sensor operation
- Exhaust leak or catalyst damage changing expected sensor voltage
Fault status
Status
P0157 — O2 Sensor Circuit Low Voltage (Bank 2 Sensor 2). Sensor signal is below expected range; possible short to ground, sensor or heater fault, wiring/connector issue, or catalytic/exhaust problem.
Repair difficulty: Medium
Diagnostic time: 0.5-2.0 hours
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