P0137 on a Mercedes-Benz: Causes, Fixes & Repair Cost

🟢 Low severity · drivable

Safe to drive — this downstream sensor only monitors the catalytic converter, so a Mercedes with P0137 can be driven while you arrange the repair.

What P0137 means on a Mercedes-Benz

On a Mercedes-Benz, P0137 means the engine computer sees low voltage from the bank 1 downstream oxygen sensor, located behind the catalytic converter. This sensor only checks converter efficiency, so low voltage usually means a faulty sensor, damaged wiring, or an exhaust leak rather than a fuel-mixture problem.

Is P0137 common on Mercedes-Benzs?

P0137 is most often seen on higher-mileage Mercedes models where exhaust heat has degraded the post-cat sensor. Wiring in the exhaust area can also become brittle, and flex-pipe or flange leaks on older C-Class and E-Class models are a common companion to this code.

Commonly reported on: C-Class, E-Class, GLK, ML.

Symptoms

Check engine light on
Usually no change in how it drives
Possible exhaust tick from a small leak
Slightly worse fuel economy if a leak is present

Common causes

most common: Faulty bank 1 downstream oxygen sensor
common: Exhaust leak before the downstream sensor
common: Brittle or damaged sensor wiring from exhaust heat
less common: Corroded sensor connector

How to fix it

Fix	DIY?	Typical cost
Replace the bank 1 downstream oxygen sensor	Yes	$100–350
Repair an exhaust leak near the sensor	Mechanic	$120–400
Repair damaged O2 sensor wiring	Mechanic	$100–300