P0420 on a Jeep: Causes, Fixes & Repair Cost

🟠 Moderate severity · drivable

A Jeep with P0420 is drivable short-term, but off-road or highway use on a failing converter can worsen the damage.

What P0420 means on a Jeep

On a Jeep, P0420 means the rear oxygen sensor on bank 1 says the catalytic converter isn't cleaning the exhaust efficiently. The engine computer compares the front and rear O2 sensors, and when they read too similarly it sets P0420. On V6 models, bank 1 is the driver's side.

Is P0420 common on Jeeps?

P0420 shows up on Wranglers, Grand Cherokees, and Cherokees with higher mileage. Off-roading can knock the exhaust out of position and cause leaks, and the 3.6L V6 is known for oil consumption that can shorten converter life.

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

Symptoms

Check engine light on
Slightly worse fuel economy
Rotten-egg smell from the exhaust
Possible rattling from the exhaust after off-road use

Common causes

most common: Worn catalytic converter
common: Faulty rear oxygen sensor
common: Exhaust leak (including damage from off-road use) before the rear sensor
less common: Oil consumption from the engine damaging the converter

How to fix it

Fix	DIY?	Typical cost
Inspect the exhaust for leaks or damage and repair them first	Yes	$50–200
Test the rear oxygen sensor and replace it if faulty	Yes	$60–200
Replace the catalytic converter	Mechanic	$600–2300

Frequently asked questions

Can I drive my Jeep with P0420?

Yes for a short time, but it's best to diagnose it soon. A failing converter hurts fuel economy, and if you off-road, a damaged exhaust can be the real cause.

Why do Jeeps get P0420?

Higher-mileage Wranglers and Grand Cherokees commonly wear out the converter or rear O2 sensor, and the 3.6L V6 can burn enough oil to shorten converter life.

How much does it cost to fix P0420 on a Jeep?

A rear O2 sensor is about $60–$200, while a converter replacement is typically $600–$2,300 depending on the model.