P0137

Code

Generic P — Powertrain

O2 Sensor Circuit Low Voltage Bank 1 Sensor 2

Brand: Generic

Type: P — Powertrain

Views: UK: 38 EN: 75 RU: 156

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Faulty Bank 1 Sensor 2 (downstream O2 sensor)
Open or shorted wiring/poor connector (sensor to PCM)
Corroded or contaminated connector pins
Exhaust leak upstream of the sensor
Fuel delivery problems causing a lean condition (low fuel pressure, injector issues)
PCM fault (less common)

Retrieve freeze frame and live data for O2 sensors and fuel trims
Compare Bank 1 Sensor 2 voltage to Bank 1 Sensor 1 (upstream) while engine is at operating temperature
Inspect sensor connector and wiring for corrosion, damage, pin push‑outs or water
Backprobe sensor signal and ground with a digital multimeter or oscilloscope
Verify fuel pressure and check for vacuum/exhaust leaks
Check heater circuit power/ground for the downstream sensor (if equipped)

Typical narrowband O2 sensor voltages: ~0.1 V (lean) to ~0.9 V (rich).
Downstream (sensor 2) usually shows a more stable voltage near mid‑range when catalyst is working; sustained voltage < ~0.1–0.2 V can trigger P0137 depending on OEM thresholds.
Expected sensor heater resistance (varies by sensor): commonly a few ohms to tens of ohms; heater current often ~0.5–1.5 A — consult vehicle spec.
Response should not be a constant low voltage; long steady low (

Read and record all stored DTCs, freeze frame, and live O2 sensor data. Note operating conditions when code set.
Visually inspect the Bank 1 Sensor 2 connector and wiring for damage, corrosion, or disconnection. Repair any damaged wiring or connectors.
With engine at normal operating temperature, backprobe the sensor signal wire and measure voltage while monitoring upstream sensor and fuel trim. Confirm sensor 2 is consistently low compared with sensor 1.
Wiggle wiring harness and connectors while watching the signal for intermittent changes to identify broken wires or poor contacts.
Check continuity between sensor signal and PCM pin; check for short to ground or 12V. Repair any wiring faults.
Verify heater circuit: with key on (engine off) check for correct supply voltage and measure heater resistance. Repair heater circuit if open.
Inspect for exhaust leaks upstream of the sensor and repair as needed.
If wiring and exhaust are good, check fuel pressure and injector operation to rule out a true lean condition.
If all circuits and vehicle systems are good, replace the Bank 1 Sensor 2. Clear codes and road test to confirm repair.
If code returns after sensor replacement, consider catalytic converter condition and PCM diagnosis.