P0420 on RAM
Catalyst System Efficiency Below Threshold (Bank 1)
P0420 on RAM vehicles indicates catalyst system efficiency below threshold (bank 1). Au7o has documented this code across 2 RAM models — most commonly on 1500, 1500 Classic. P0420 means the engine computer determined the catalytic converter on Bank 1 isn't cleaning the exhaust as efficiently as it should. The computer compares the upstream and downstream oxygen sensors; a healthy converter stores and releases oxygen, so the downstream sensor should read fairly steady, while a worn one lets its readings mirror the upstream sensor. When that efficiency falls below a set threshold, this code is set. While it most often points to a worn-out catalytic converter, it can also be triggered by upstream problems like a faulty oxygen sensor or an exhaust leak, so the converter isn't always the actual fault. Typical repair costs on RAM range from $100 to $1,500, depending on the specific model and root cause.
Common Causes of P0420
- •Worn-out or failing catalytic converter (Bank 1)
- •Faulty or aged downstream (or upstream) oxygen sensor
- •Exhaust leak before or near the oxygen sensors
- •Engine running rich or lean (fuel trim issues)
- •Misfires or oil/coolant contaminating the converter
- •Damaged or aftermarket low-quality catalytic converter
- •Faulty oxygen sensor wiring or connectors
- •Software/calibration needing update (on some vehicles)
P0420 on RAM by Model
RAM 1500(1 issue)
- Exhaust Manifold Bolt Breakage2009-2019
The exhaust manifold bolts on HEMI engines are prone to breaking due to heat cycling. Broken bolts cause exhaust leaks, ticking noise on cold start, and potential exhaust smell in cabin. The rear bolts on both sides are most commonly affected.
RAM 1500 Classic(1 issue)
- 5.7L HEMI Exhaust Manifold Bolt Breakage2019-2024
The exhaust manifold bolts on the 5.7L HEMI break due to thermal cycling, causing an exhaust leak with a ticking sound that is louder on cold starts and quiets as the engine warms up.
Looking for P0420 on a different make?
View P0420 across all makes →Frequently Asked Questions
What does P0420 mean on RAM?▼
P0420 stands for "Catalyst System Efficiency Below Threshold (Bank 1)." P0420 means the engine computer determined the catalytic converter on Bank 1 isn't cleaning the exhaust as efficiently as it should. The computer compares the upstream and downstream oxygen sensors; a healthy converter stores and releases oxygen, so the downstream sensor should read fairly steady, while a worn one lets its readings mirror the upstream sensor. When that efficiency falls below a set threshold, this code is set. While it most often points to a worn-out catalytic converter, it can also be triggered by upstream problems like a faulty oxygen sensor or an exhaust leak, so the converter isn't always the actual fault. On RAM specifically, this code is documented across 2 models.
What causes P0420 on RAM vehicles?▼
Common causes on RAM: Worn-out or failing catalytic converter (Bank 1), Faulty or aged downstream (or upstream) oxygen sensor, Exhaust leak before or near the oxygen sensors, Engine running rich or lean (fuel trim issues), Misfires or oil/coolant contaminating the converter. Specific causes vary by model and year — see the per-model sections below.
How much does it cost to fix P0420 on a RAM?▼
Repair costs on RAM range from $100 to $1,500, depending on the specific model and root cause.
Which RAM models have P0420 documented?▼
Au7o has documented P0420 on 2 RAM models: 1500, 1500 Classic.