Code
P1137
CHRYSLER
P — Powertrain
HO2S Bank 1 Sensor 2 Lean Or Low Voltage
Views:
UK: 25
EN: 43
RU: 31
AI status
Completed
Completed
100%
Causes
- Faulty Bank 1 Sensor 2 (HO2S) — sensor element or internal heater failure
- Open/short/damaged sensor wiring or poor connector/ground
- Exhaust leak upstream of the sensor (introducing excess air)
- Fuel system issues causing lean condition (low fuel pressure, clogged injector)
- Intake vacuum leak or unmetered air
- Faulty upstream sensor (Bank 1 Sensor 1) or MAF giving incorrect fuel trims
Symptoms
- Check Engine Light (MIL) illuminated
- Possible decreased fuel economy
- Possible rough idle or hesitation if upstream issues are present
- Failed emissions test or poor catalyst monitoring readiness
- No obvious drivability symptoms if fault is isolated to downstream sensor
What to check
- Read and record freeze frame and all stored codes (including pending codes)
- Compare live O2 voltages: Bank 1 Sensor 1 (upstream) vs Bank 1 Sensor 2 (downstream)
- Inspect sensor connector and wiring for damage, corrosion, or poor ground
- Visually inspect exhaust for leaks before Bank 1 Sensor 2 and around manifold/downpipe
- Check fuel pressure and perform injector balance if fuel delivery suspected
- Scan fuel trims (short and long term) and MAF/boost/vacuum data for evidence of lean condition
Signal parameters
- Typical narrowband O2 sensor voltage range: ~0.1–0.9 V (lean ≈ 0.1–0.3 V, rich ≈ 0.7–0.9 V)
- Downstream (Sensor 2) normally more stable than upstream; often centered near ~0.4–0.6 V when catalyst efficient
- Code sets when sensor 2 reports low voltage (lean) below manufacturer threshold (commonly < ~0.2 V) for a set time
- Heater circuit: supply ≈ 12 V with expected resistance typically a few ohms up to tens of ohms (refer to service manual for exact value)
- Upstream sensor should switch frequently in closed loop; downstream should show less switching if catalyst is working
Diagnostic algorithm
- Verify code and capture freeze-frame. Note engine conditions (temp, load, fuel trims).
- Inspect Bank 1 Sensor 2 connector and wiring for corrosion, damage, pin push-out, or poor ground. Repair any faults found.
- With the engine warmed, use a scan tool to monitor Bank 1 Sensor 1 and Sensor 2 voltages and compare behavior. Sensor 2 stuck low while Sensor 1 switches lean/rich suggests sensor/circuit or exhaust leak.
- Check heater circuit: with key ON, measure supply voltage and ground at the sensor connector; measure heater resistance with sensor disconnected and cold (compare to spec). Replace sensor if heater open/short.
- Perform a smoke test for intake/vacuum leaks and inspect exhaust for leaks upstream of Sensor 2. Repair leaks and retest.
- Check fuel pressure and flow. If low, diagnose fuel pump, filter, regulator, or faulty injectors.
- Introduce a controlled rich source (small propane puff into intake) while monitoring O2 voltages: upstream should go rich quickly; downstream may show a smaller change. If downstream never responds, suspect sensor or wiring.
- If wiring and fuel/air/exhaust are good and downstream still reads low, replace Bank 1 Sensor 2 with OE-specified HO2S. Clear codes and test drive to confirm code does not return.
- If replacement does not resolve, verify catalytic converter condition and perform ECM diagnostics or reflash if indicated.
Likely causes
- Damaged sensor harness or corroded connector on Bank 1 Sensor 2
- Vacuum or exhaust leak near Bank 1 exhaust manifold/downpipe
- Weak fuel pressure or lean fuel delivery to bank 1
- Failed HO2S element (sensor aged or contaminated)
- Heater circuit failure for the downstream sensor
Fault status
Status
HO2S Bank 1 Sensor 2 reports a sustained low/lean voltage. Possible causes include sensor or heater failure, wiring/connector issue, exhaust or intake leak, or lean fuel condition. Further diagnosis required.
Repair difficulty: Medium
Diagnostic time: 1.0-2.5 hours
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