Hi all,

this is my first post here so please go easy on me. I don't have much technical experience with cars either, but I'm trying...

I get these errors on VCDS. I also have noticed that the water temperature drops randomly to half the normal reading and then may come back again to normal. Do you suggest that I start by changing the engine coolant sensor? Could the other problems also be related to that? I have found in other threads suggestions that they could be related...

Thank you for your help

Monday, 26 December 2011, 15:33:29:0

VCDS-Lite Version: Release 1.0

Control Module Part Number: 036 906 034 DF

Component and/or Version: MARELLI 4MV 4563

Software Coding: 00071

Work Shop Code: WSC 25255

Additional Info: TMBMD46YX33692782 SKZ7Z0B1621173

3 Faults Found:

16804 - Catalyst System; Bank 1: Efficiency Below Threshold

P0420 - 35-00 - -

16502 - Engine Coolant Temp. Sensor (G62): Signal too High

P0118 - 35-10 - - - Intermittent

17550 - Load Calculation Cross Check: Lower Limit Exceeded

P1142 - 35-10 - - - Intermittent

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Definately replace the coolant sensor, as it is being reported as having a problem and you have seen the coolant temperature display back that up. After that clear the other faults (print them out first - or save them).

Definately replace the coolant sensor, as it is being reported as having a problem and you have seen the coolant temperature display back that up. After that clear the other faults (print them out first - or save them).

Thanks for that! Will do it ASAP

16804 - Catalyst System; Bank 1: Efficiency Below Threshold

P0420 - 35-00 - -

All this one is the result of the % difference of reduction of emmisssions between the two lambda sensors. There has to be a minimum % reduction (cleaning) after the exhaust gasses pass throught the two cats. If it falls out of this range it tends to trip this code.

I had this problem as my emissions were very low on the tests (so not much to clean anyway) and the race cats could not scrub the emissions any cleaner to get the minimum % required between the two lambda sensors! I ended up ditching the race cats (200cell) and refitting the OEM ones and "strangulating" the engine in the process. Emissions have changed (so minor it's not true) just enough to produce the required amount of "scrub" and the code no longer trips!..