" Basically,
there is nobody in the system that knows how to troubleshoot a vehicle
without totally relying on the computerized hardware. The programming
is not intended to nail down the exact cause of a problem, only the
most probable causes, expecting the dealer to replace things in a
rational and logical order based on their experience. "

Not even that. I think they may have been trying to rake you over the coals.. As far as I know, there is no code for "catalytic convertor". the second O2 sensor is supposed to detect slightly less oxygen than the first one. This assures the cat is installed and operating. the codes them selves read something like "O2 sensor #2 reading rich", or lean. Anyone with a brain should logically replace that first. Incidentally, for this system to work, it MUST waste some fuel by making it over rich. If the mixture is stoichometric, the catalytic has nothing to do. But that is a bit easier on the valves and a few other components.

Catalytics either get clogged or burnt out. Something has to happen, prolonged driving with a misfire for example. I don't know about you, but when I drive, I want the car to run right. If it has a miss I can't stand it. If anything I can't stand it. If it burns oil I junk it. (that's why I prefer GM, seems their engines and trannies last, problem is they fell out of the damn car back in the 1980s)

You know, if the auto service business was like the consumer electronics service business, they would have pretty much had to put that cat in for free, or lied to you and put the O2 sensor in for free. Guess which. And let's not even get started about doctors, them ****ers cut off the wrong leg and expect to get paid. And that is pretty bad, because if you have one leg there ARE solutions whereby you can walk. If you have no legs that is it. I hope the guy they did that to is the richest MF sitting in the world.

But anyway, for a time I was the go to guy on hard faults in cars. (I also learned that you can CLEAN an O2 sensor) Buddy brings me his Cutlass, one of the last years you could get the bulletproof 4-151 engine. Good reliable car. Runs like ****. It REALLY REALLY acts like low fuel pressure. (a later paragraph will discuss that) Alot of cars had low fuel pressure and would start and idle, and crawl but not run. Slow fuel delivery was a big thing for a while. But that has been checked. It has also been to Mr. Goodwrench for a fifty buck diagnosis and they said to replace the engine.

They didn't know who the **** they were talking to. They were trained to replace parts for fifty bucks an hour, we degreed cams, we had cranks machined down a thousandth or two and had them hard chromed back up to size. This is like having a forged crank, in fact better in some way. the olman had a 283 that did 9,400 RPM with a Racer Brown roller cam, ONE RPM higher it would wipe out bearing number one. They tried many things but at 9,400 RPM the laws of physics takes over and there was nothing you could do.

So anyway I drives the car up down the street, it cannot get out of its own way. Checking things out, I find the two possibilities are this crank sensor which is a bitch to change, or it jumped time. I took the air cleaner off and revved it up, and during part of the stroke it was spitting the injected gas out the top.

I said "Tear down for timing chain". (This guy was also a competent mechanic but this was a tough case) He said that they said this car does not have a timing chain, it has gears.

The next day he shows up and throws the tensioner on my kitchen table. Doesn't have a chain eh ? What kind of gears need that kind of tensioner ?

Another time my ex-lawyer had this pickup truck, I forget the make and model but it was a cheapie. It had linear torsion bar suspension, which means all the front end parameters are different. He had a tow hitch on a tow bar on the front so he could tow it with his camper. He said this is the only truck I could find that you could back up without the steering wheel whipping to a lock. It would track, and back up nicely so he wanted to keep it. Go camping and take your car with you kinda thing.

Maybe a year or so before he had the timing belt replaced. It would intermittently run like ****, not start, whatever. Nobody could figure it out.

Turns out the dodo who did the belt had lost the woodruff key and replaced it with an American version which was a bit too small. Over time it sheared, and the crank went where it wanted. Literally like 180 degrees off.

Now that is hard to detect. But we did detect it. We had to drive it too, apparently the inertia of revving and idling made it do it. Eventually we caught it, at one time the timing marks are right, and then they are wrong. W T F !

The wrong woodruff key had already mauled the crank so we brazed one in. You don't want to weld something like that in case it ever needs a front crank seal, but the brazing, and we thought about this, would stop the movement which was responsible for the failure because it just kept wearing away at it. Every compression and then power stroke moved it as this key was between the crank and the damper.

OK, that is not necessarily consumer electronics but others had looked at the thing coming up with all the wrong diagnoses. So it already had brand new plugs, module, sensors, wires, high performance lugnuts, the works.

How come some people are responsible if their diagnosis is incorrect and others are not ?