Vag Com fault reading

[bbewekim]

Component: MARELLI 4MV 5018
Coding: 00071
Shop #: WSC 00488
WVWZZZ9NZ3Y102783 VWZ7Z0B5625101

1 Fault Found:
16804 - Catalyst System; Bank 1: Efficiency Below Threshold
P0420 - 35-00 - -
Readiness: 0000 0000

car is a 1.4 100bhp.

cant pinpoint the exact problem anyone had any problems with similar faults?

Its the post cat lambda which is picking up the fault? Could it be the precat lambda failing?

 

[rocky2008]

bank 1 is the sensor befor the cat, mine flashes up with this problem from time to time

 

[meltonlad]

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

Special Notes
For 1.8T's experiencing this fault code, this thread may be useful: http://forums.vwvortex.com/zerothread?id=663057