P0137
- Powertrain
- Generic (SAE)
- Emissions
Diagnose soon
Usually safe to drive short distances, but the fault will not clear itself and can worsen or fail an emissions test.
O2 Sensor Circuit Low Voltage (Bank 1, Sensor 2)
This code is in our catalogue but has not yet been through editorial review, so the guidance below is limited to what our structured data supports. We publish deeper diagnostic content only after a code has been reviewed — here is why.
The downstream oxygen sensor signal is fixed at a low voltage. Either the catalyst is letting unburned oxygen through (sensor sees lean), the sensor itself is shorted to ground, or the catalyst is so degraded that the downstream signal mirrors a lean upstream condition.
A trouble code records what a control module measured. It does not identify which part failed. Test before replacing anything.
- Safe to drive
- Usually safe to drive short distances, but the fault will not clear itself and can worsen or fail an emissions test.
- Urgency
- Diagnose soon
- Will it pass emissions
- No
- Check engine light
- Solid
- Clearing the light
- A completed drive cycle is normally required before the monitor re-runs and the light can clear.
- Increased fuel consumption
- Possible rough idle or hesitation
Many vehicles show no symptom at all beyond the warning light. The absence of a symptom does not mean the fault is not real.
| # | Cause | How often | Component |
|---|---|---|---|
| 1 | Signal wire shorted to ground | Common | — |
| 2 | Catalyst degraded (often appears before P0420) | Common | — |
| 3 | Exhaust leak between catalyst and downstream sensor | Occasional | — |
Ordering reflects how often each cause is responsible in general, not a probability for your vehicle. Confirm by testing.
- Catalytic Converter
- Oxygen Sensor Downstream
- Definition
- Generic code set (SAE J2012 / ISO 15031-6) via the OBDexopen database, dedicated to the public domain under CC0-1.0.
- Diagnostic guidance
- Written and reviewed in-house. See our editorial policy.
- Review status
- Awaiting review
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