P0137 — Oxygen sensor signal is too low after catalytic converter
The oxygen sensor after the catalytic converter is reporting a voltage lower than expected. This usually means the sensor is not detecting enough oxygen in the exhaust, which can indicate a failing sensor, wiring issues, or problems with the catalytic converter.
Common causes
The cause is almost always one of a few things. Here they are — P0137 rarely comes from anything outside this list:
- Faulty oxygen sensor (bank 1 sensor 2)
- Damaged or corroded sensor wiring/connectors
- Exhaust leaks near the sensor
- Failing catalytic converter
- Engine running too lean or rich
Where to start
In the order a sensible mechanic would work — the cheap checks first, the expensive replacements only after:
- Inspect and repair sensor wiring and connectors
- Check for and fix exhaust leaks near sensor
- Test catalytic converter function
- Replace oxygen sensor if faulty
- Replace catalytic converter if needed
That is what holds for P0137 in general. From here it depends on your engine — tell me which car it is and what it does, and I will give you the steps for it: real procedures, torque figures and diagrams instead of general advice.
Why TorqFix for your car?
Above is what the code means and why it appears. TorqFix goes further — it gives you specific procedures, torque values, wiring diagrams and pinouts for your exact engine, not generic steps for every car. Real workshop data (127,000+ diagrams, 10,000+ procedures), interpreted by AI in your language.
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Code breakdown
🔧 Related repair procedures
- VW: Checking Lambda probe and Lambda control before catalytic converter
- AUDI: Removing and installing front exhaust pipe with catalytic converter
- AUDI: Removing and installing front exhaust pipe with starter catalytic converter
- AUDI: Removing and installing front exhaust pipe (right-side) with catalytic converter - vehicles with manual gearbox
- AUDI: Checking lambda probe and lambda control downstream of catalytic converter
- AUDI: Removing and installing front exhaust pipe (right-side) with starter catalytic converter and main catalytic converter - vehicles with manual gearbox or multitronic gearbox 01J
- AUDI: Removing and installing catalytic converter
- AUDI: Removing and installing front exhaust pipe (left-side) with catalytic converter - vehicles with multitronic gearbox
- AUDI: Removing and installing catalytic converter - vehicles with two turbochargers
- AUDI: Removing and installing catalytic converter with exhaust pipe - vehicles with engine code letters AVF, AWX
Who makes these pages, and how
TorqFix was built by a mechanic — after a 2,700 km drive with five roadside repairs that no diagnostic tool could explain.
The figures on this page come from manufacturer workshop documentation and are shown as they are. The page is assembled automatically from that data — it is not written by an AI. The AI works in the chat, where it answers for your specific car. It writes nothing here.
The same code can mean different things on different makes. Match the meaning to your make before acting on it.
Seen a figure that does not match your manual? Write to us — we correct it and note when. support@torqfix.com
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