Q: P0420 code. Jeep wrangler 2011 with 111000 miles. Code disappears after appearing. Light lawnmover sound on acceleration

asked by on

Jeep is making a motorcycle/go cart type sound on cold start, when warmed up the sound subsides a HUGE amount and you can barley hear it, engine shoots P0420 code when gas is put in engine, also on occasion when driving, then it disappears about 50 miles later, and reappears. EGR valve has been replaced. I have noticed a gap between the manifold pipe and the down pipe under the jeep under the drivers side of the car. Also when the EGR valve was replaced was told manifold bolts were loose and they were tightened.

My car has 111000 miles.
My car has an automatic transmission.

The P0420 code relates to catalyst efficiency however many of the underlying causes of the code have nothing to do with a fault in the converter itself. To evaluate that code, among the data of interest are long and short term fuel trims and a mechanic would obtain that data from an automotive scanner. The reason the data are important is catalyst overheating from lean burn is one of the causes of P0420. In your circumstance it sounds like you might have an exhaust leak. For safety reasons, all exhaust leaks should be investigated and repaired before diagnosing the P0420 code or ANY trouble code. To have the exhaust leaks pinpointed, and repaired as necessary, the recommended service is an exhaust leak diagnostic. If you request that service, the responding certified mechanic will fix the leaks and then deal with the P0420 trouble code. If you have further questions or concerns, do not hesitate to re-contact YourMechanic because we want you to make the most of your repair dollars and help you to get the best possible results.

Was this answer helpful?
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details
  1. Home
  2. Questions
  3. P0420 code. Jeep wrangler 2011 with 111000 miles. Code disappears after appearing. Light lawnmover sound on acceleration

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Fair and transparent pricing

Get a quote

What others are asking

Q: Car Temperature Rising

You should first confirm that the temperature controlled radiator cooling fans are functioning. If they are not working, or not working well, that would cause overheating at idle. The only way to condemn a radiator, other than if it is...

Q: 42rle transmission driveshaft have different part numbers.

The best thing to do is cross reference the part number with the dealership and the parts store. Keep in mind, the part number on your jeep is from the dealership and not a local parts store. So if you...

Q: My car was recalled last year for power steering failure and it was fixed.

This is a vehicle safety issue. You can contact Ford Motor Company, at their main customer service number, and also contact the National Highway Traffic Safety Administration (NHTSA) Vehicle Safety Hotline at 1-888-327-4236 (TTY 1-800-424-9153), or go to www.safercar.gov. You...

Related articles

How Long Does a Heater Control Valve Last?
Keeping the right amount of coolant in a car is essential in keeping the engine at the right temperature. Failing to have the right amount of coolant or even bad elements...
P0240 OBD-II Trouble Code: Turbocharger Boost Sensor B Circuit Range/Performance
P0240 code definition Turbocharger Boost Sensor B Circuit Range/Performance What the P0240 code means P0240 is an OBD-II generic code triggered when the Engine Control Module (ECM) detects the intake boost...
How Much Does a Mechanic Make in Vermont?
Automotive technician jobs in Vermont have an average mechanic salary of $37k, with some mechanics earning a salary of $53k.