Code
P1157
CHRYSLER
P — Powertrain
HO2S Bank 2 Sensor 2 Lean System Or Low Voltage
AI status
Completed
Completed
100%
Causes
- Faulty HO2S (Bank 2 Sensor 2) sensor
- Open/short or high resistance in sensor wiring or connector corrosion
- Heater circuit failure (open heater element or blown fuse/relay)
- Exhaust leak upstream of or at the sensor location
- Vacuum/air intake leak or restricted fuel delivery causing true lean condition
- Failing catalytic converter (affecting downstream readings)
Symptoms
- Check Engine Light (MIL) illuminated
- Reduced fuel economy
- Possible rough idle or hesitation if lean condition is severe
- Failed emissions test (high O2 readings, downstream sensor out of expected range)
- Possible stored freeze frame data showing low downstream O2 voltage
What to check
- Scan for all stored and pending codes; record freeze frame and live PIDs
- Observe live data: Bank 2 Sensor 2 voltage and compare with Bank 2 Sensor 1 (upstream) and Bank 1 sensors
- Check short‑term and long‑term fuel trim for Bank 2 (elevated positive trims suggest real lean)
- Visually inspect sensor and wiring harness for damage, corrosion, heat damage, or splices
- Perform a smoke test or otherwise check for intake/exhaust leaks on Bank 2
- Check fuel pressure and injector operation to rule out fuel delivery lean condition
Signal parameters
- Upstream (Sensor 1) HO2S typical switching range: ~0.1–0.9 V (rapid switching)
- Downstream (Sensor 2) HO2S expected: relatively steady ~0.3–0.6 V (slow/less switching); should not sit persistently below ~0.1 V
- Low voltage/lean indication:
- High voltage/rich indication: >0.8 V
- Heater element resistance (generic): typically low ohms (manufacturer specific) — commonly ~2–20 Ω; heater supply should be near battery voltage with key on
- Response: downstream sensor should show smaller amplitude and slower changes than upstream sensor
Diagnostic algorithm
- Retrieve freeze frame and stored codes; clear codes and perform monitored driving cycle to reproduce
- Inspect sensor and harness: look for physical damage, burns, pin corrosion, rodent damage and repair as needed
- Check for exhaust or intake leaks on Bank 2 using visual inspection and a smoke/leak test; repair leaks and retest
- Using a scan tool, monitor Bank 2 Sensor 1 and Sensor 2 voltages and Bank 2 fuel trims while creating a controlled rich/lean change (e.g., snap throttle, fuel pressure test) to see if Sensor 2 follows expected behavior
- Measure heater circuit: with connector disconnected, measure heater resistance and compare to spec; verify heater power and ground with key on
- Backprobe sensor signal while cranking/running: verify voltage levels and switching characteristics; verify no short to ground or Vbypass
- Check fuel pressure and adjust/repair if out of spec; verify injectors on Bank 2 are operating correctly
- If wiring or heater faults found, repair/replace harness, connectors, or fuses/relay as required
- If wiring and fuel system are good but sensor output remains abnormal, replace Bank 2 Sensor 2 with an OE or equivalent part and retest
- If symptoms persist after sensor replacement, evaluate catalytic converter efficiency and PCM/ground integrity
Likely causes
- Damaged or contaminated Bank 2 Sensor 2
- Broken wiring, damaged connector, or poor ground on sensor circuit
- Failed sensor heater element or heater power supply/fuse
- Exhaust leak at bank 2 downstream/exhaust manifold leak upstream that affects sensor readings
- Fuel system lean condition (low fuel pressure, clogged injector)
- Catalytic converter degraded on bank 2
Fault status
Status
The vehicle detected a lean or low voltage condition from the downstream O2 sensor on bank 2. This may indicate a sensor or wiring problem, an actual lean condition, or exhaust/catalyst issues. Service and diagnosis recommended.
Repair difficulty: Medium
Diagnostic time: 1-3 hours
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