Posted by marino pacini on February 12, 2007, 11:17 am
Hello guys got one i could do with some help please. this car has a history of mil light coming on but i suspect the fault has changed as the dealer fitted 2 cats 2 lambdas etc. came to us we code read it and got p0420 catalyst system efficiency below threshhold . and po555 throttle valve control position nominal vs actual comparison. cleared codes and road test they did not return so scanned actual values all appered good so asked him to try it. after 300 miles light came on and he called back in. po555 code back. checked wiring for breaks etc and advised by dealer to renew throttle housing at £300 plus. had one in stock. so told customer and he agreed. ( i should point out it is drive by wire system) well after 300 miles it comes back on and then every trip after first time. had it back sent it to vauxhall specialist to go on tec 2 he did a software upgrade and reset learning parameters. 300 miles later comes on again.any suggestions it never does it to us . always po555 code returns. thanks marino