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Model specific boards => Golf mk4 => Topic started by: Tim1111 on 02 October 2012, 21:18
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Hope someone can help me sort a problem on the wife's Golf (2003 1.6 16V - BCB I think from memory).
Emissions light has come on 3 times in the past month. I've cleared it each time and it stays off for about a week or so then reappears. Each time it throws up 3 codes:
16555 - P0171: Fuel trim - System lean (Bank 1)
16786 - P0402: Exhaust gas recirculation flow excessive
16804 - P0420: Catalyst system efficiency below threshold (Bank 1)
She had a hole in the front exhaust which I've bandaged up hoping that was the cause (apparently not as it's just come on again :cry:). But still get the occasional chugging on idle (bounces up and down between 600-900 rpm, rather than it's usual constant 700ish). I also noticed when I drove it on the motorway the other day on a long journey that occasionally (happened twice in about 2 hours) the revs dropped off momentarily - cruising along then the revs dropped down to about 2500 then returned to normal all in less than a second.
One other point to note is that the light seems to come on after I've driven it (may be coincidence or could be my heavier right foot :whistle:)
Anyway, over to you guys. Can someone point me in the right direction of possible causes to investigate?
Thanks for your help
Tim.
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I've been pointed in the direction of these on another forum:
http://wiki.ross-tech.com/wiki/index.php/16555/P0171/000369
http://wiki.ross-tech.com/wiki/index.php/16786/P0402/001026
http://wiki.ross-tech.com/wiki/index.php/16804/P0420/001056
It looks like from these likely causes could be:
•Leakage in Intake and/or Exhaust System
•Catalyst faulty
•Oxygen Sensor(s) faulty
•Oxygen Sensor(s) Control faulty
•Exhaust Gas Recirculation (EGR) Valve stuck open/leaking/faulty
•Exhaust Gas Recirculation (EGR) System leaking/faulty
•Wiring and/or Connector(s) from/to Exhaust Gas Recirculation (EGR) Valve faulty
•Mass Air Flow Sensor (G70) defective
•Intake System Leak(s)
Question is, would any of the above be likely to trigger all three codes each time and therefore be the most likely culprit?