"Jeff Liebermann" wrote in message
...
On Thu, 28 Feb 2013 19:39:11 -0800, "William Sommerwerck"
wrote:

Well, that's part of the problem. In a parallel effort, a different
friend and one of his accomplices are currently trying to troubleshoot
a non-functional Mercedes ML320. My guess is $200 in wasted money on
parts that were not defective so far. The problem is that despite my
advice on approaching the troubleshooting in a logical and systematic
manner, they've been floundering around for several days without any
useful results.



The problem with cars is that they flag up error codes that are erroneous.
If you have an intake air leak, for example, the Mass Airlow Sensor gives an
incorrect reading of how much air is entering the combustion chambers, so
the fuel is adjusted accordingly and erroneously, which changes the reading
from the Oxygen sensor.
The car will tell you the Oxygen Sensor or the MAF is faulty, which people
(including mechanics in garages who often don't have a scooby what they are
doing) will replace at great expense to no effect, but still give you the
bill.



Gareth.