[MBFXHF]

Newbie to this forum,

I have a 2001 VW Jetta TDI with 186,000 miles. The check engine light comes on after driving one mile or more. I checked the ODB II, and received an error code of P0420. I had the motor replaced last year and it had the same error code before and after the swap. I replaced the EGR value and still the same problem. All help will be appreciated.

 

[chittychittybangbang]

Not sure but post moved to mk4 section since it's a specific technical question. Here is what ross tech's wiki says:

16804/P0420/001056 - Catalyst System; Bank 1: Efficiency Below Threshold

Possible Causes

• Leakage in Intake and/or Exhaust System
• Catalyst faulty
• Oxygen Sensor(s) faulty
• Oxygen Sensor(s) Control faulty

Possible Solutions

• Check Intake and Exhaust System for Leaks
• Check Catalyst
• Check Oxygen Sensor(s)
• Check Oxygen Sensor(s) Control
  • Perform Oxygen Sensor(s) Aging Check

 

[MBFXHF]

Thanks for information. I will check the catalyst. In the future I will try to post in the correct section.