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.
Definition per SAE J2012 standard nomenclature. Symptoms, causes and costs are editorial guidance - always confirm with a diagnosis of your specific vehicle.