P0138 on a Jeep: Causes, Fixes & Repair Cost

🟢 Low severity · drivable

Safe to drive — this downstream sensor only monitors the catalytic converter, so a Jeep with P0138 can be driven while you arrange the repair.

What P0138 means on a Jeep

On a Jeep, P0138 means the engine computer sees high voltage from the bank 1 downstream oxygen sensor behind the catalytic converter. This sensor only monitors converter efficiency, so high voltage is almost always a faulty sensor or a wiring short rather than a rich fuel mixture. On V6 Jeeps, bank 1 is the right-hand bank.

Is P0138 common on Jeeps?

P0138 is most common on higher-mileage Jeeps as the downstream sensor fails, and off-road exposure can make wiring problems worse. Grand Cherokee and Wrangler models with V6 engines see it most, and mud or water in connectors can cause odd voltage readings.

Commonly reported on: Wrangler, Grand Cherokee, Cherokee, Compass.

Symptoms

Check engine light on
Usually no change in how it drives
Possible reduced fuel economy
Sometimes no noticeable driving symptoms

Common causes

most common: Faulty bank 1 downstream oxygen sensor
common: Sensor wiring shorted to power
common: Mud, water, or corrosion in the sensor connector
less common: Failing catalytic converter

How to fix it

Fix	DIY?	Typical cost
Replace the bank 1 downstream oxygen sensor	Yes	$70–250
Repair shorted sensor wiring or a corroded connector	Mechanic	$70–280
Replace the catalytic converter if it's failing	Mechanic	$800–2500