FAO VW or Bentley technicians

[danny_p]

P codes  learnt that the hard way.

what the P code says , and what it actualy is  ,,,,, the differance can be inpressive

[dazzawest1987]

haha, really? i've got a vw dealer near me, i'll get my boss to take his car down there and get them to read the fault code quickly.

thanks for those documents topher, they'll be really usefull

cheers
darren

[Agreeable Slick]

They fire hot air In to the engine to warm the cats up when cold

Is this EGR or is there a seperate feed?

Only curious as most manufacturers have a injector spraying fuel into the CAT to aid heating and I can't work out how just firing hot air in to the engine would aid warm up as the exhaust would be much hotter than any kind of hot air that could be provided....

[topher]

the extra fuel is already there thanks to the warm-up enrichment (cold start/choke). the secondary air injection does just that, adds extra air after the exhaust valves. Bosch refer to it as thermal afterburning which sounds cool, but is rather dull its kind of like an egr system but is only active for about 30 seconds.

[dazzawest1987]

for slick quick description of operation,
The secondary air system reduces
exhaust emissions in the cold starting phase.
During a cold start there is an increased
percentage of unburned hydrocarbons.
The catalyst cannot process this quantity as it has
not yet reached its operating temperature and a
mixture must be present from lambda 1.
The level of oxygen in the exhaust gases is
enriched by injecting air behind the exhaust
valves. This causes afterburning. The heat this
releases brings the catalyst to its operating
temperature more quickly.