P0137: O2 Sensor Circuit Low Voltage Bank 1 Sensor 2
A generic powertrain (engine and transmission) trouble code, same meaning on every brand.
Yes - the downstream sensor only monitors the converter.
Symptoms
- Check engine light, usually nothing else
Likely causes, most common first
- Downstream O2 sensor failure
- Exhaust leak near the rear sensor
- Wiring damage under the floor
Read P0137 yourself before paying for diagnosis
A basic Bluetooth OBD-II scanner ($20-40) plugs into the port under the dashboard and shows this code with live sensor data on your phone - useful both for confirming the fix and for talking to a shop from an informed position.
What is going on and how it gets diagnosed
P0137 reports low voltage from the post-catalyst oxygen sensor on bank 1. That sensor grades the converter's work and barely influences how the engine runs - hence the absence of symptoms.
The practical concern is inspection readiness and masking: a dead rear sensor cannot warn you about a dying converter. An unhurried but not indefinite repair.
Repair options and cost
Typical US independent-shop ranges, parts and labor. Dealers run higher; regional labor rates vary.
Cars that report P0137 most often
Based on mentions of this code in NHTSA owner complaints.
Frequently asked questions
Can I drive with P0137?
Yes - the downstream sensor only monitors the converter.
How much does it cost to fix P0137?
Typical US repair costs range from $80 for the simplest fix (downstream o2 sensor) to $400 in the worst case. The right number depends on which cause your car has - see the causes list.
Related codes
The codes closest to P0137. They often appear together, and telling them apart is usually what narrows the diagnosis.
Definition per SAE J2012 standard nomenclature. Symptoms, causes and costs are editorial guidance - always confirm with a diagnosis of your specific vehicle.