Posted by ROGER JORDAN on March 14, 2008, 12:31 am
Hi all, This one is giving me some grief, repeatedly sets code 16556, sailed through MoT emissions test, no problems at all (sorry left the readings at work), after scoping lambda sensors and Maf meter decided to change Maf as output terrible, hash all over the place, replaced Maf with new (Fuel parts) and scope trace copybook perfect, (before anyone says anything about non genuine Maf meter , judging by the number of Bosch ones we all replace I don`t reckon they can be all that hot! )I will scan old and new Maf traces and post as they might be of use to someone, the pre cat sensor is switching perfectly at idle and 3,000 rpm but is definitely switching slightly high topping out at 0.9v or thereabouts although I have seen this on other vehicles with no problem, post cat is running steady at around 0.5v Ran the car for a couple of hours with Pico hooked up to coolant sensor with hardly a ripple in the voltage at full temperature around 0.5v as I have heard these sensors can be a problem, this one has the early black body rather than the later green one. Just bought Vag-Com so on a steep learning curve (vertical) short term fuel trim is jumping all over the place from -13 to +14 sometimes it takes a week to bring on management light sometimes three weeks and of course never when we have the car, we have the car at present while owner on holiday and I`ve bought the Launch CRecorder to test it, been on all week and sods law no problem. Throttle body is clean. Have fitted new NGK plugs and against my better judgement a new genuine pre cat sensor at dealers insistance, sure enough no difference at all, a case of shooting the messenger !! This is an ex sales car so the customer is not paying otherwise I would not have changed the lambda sensor, sorry for the long post but wondered if anyone had been down the same road, needless to say car drives beautifully. Best regards Roger. PS CRecorder looks to be a very good piece of kit for this sort of job even if you do go bog eyed studying all the data.