Silver Bullets don't make for a real diagnostic routine

In one of the classes I present I have a point where I paint a little picture for the techs and the shop owners and it goes like this.

Picture you have a 2005 Chevrolet Malibu come into the shop and its setting a P0101 Mass Airflow sensor performance. You test the system and confirm the sensor has dropped out of calibration, replace it and road test the car confirming that it is indeed repaired.

Now imagine nineteen more Chevrolet Malibu's and every one of them set that same P0101, and every one of them is repaired by replacing the mass airflow sensor. "How do you approach the twenty-first Malibu that shows up at the shop setting a P0101?"

In your perspective Steve, (Steve is a moderator on another forum) and in the ideas of anyone who works like you are thinking, you would replace the mass airflow sensor and ship the car. But what if that doesn't fix this car and the light comes back on setting the same code? In that customers eye's they got ripped off, you don't know what you are doing, and they would be correct. (Never mind the fact that you got it right twenty times) The correct answer for that twenty first Malibu should have been to test it exactly the same as you did the first one, and the nineteen in-between and the details would have led you to find the restricted exhaust, or whatever caused the volumetric efficiency of the engine to fall below design expectations. That by the way is what the code really means which is that the airflow being reported by the mass air sensor at a given engine speed and throttle opening is below the threshold value. Sure a sensor under-reporting the airflow will generate that code but its not the only reason that could happen.

The trap here is someone who pulls the code, and throws the part if they get it right can be really fast and can in fact make themselves more money while they are risking getting caught doing sloppy work. The tech who stays disciplined in his/her approach gets it right every time, but since that takes longer, they actually in many cases make less money by the end of the week. What's worse is when that twenty-first car comes back, shops often direct that not to the tech who did the first repair, but to the one who will make sure to figure out what is wrong and solve the problem. Oh, and since its a comeback that means the customer likely isn't getting charged so there is no diagnostic time to be paid and that means the tech isn't getting paid either, well at least not directly. When I worked at the dealership they would promise to "make up the time" by giving me pre-delivery inspections, or other gravy tickets. (The same kinds of work that have grown to be known as wallet flushing)

As far as finding sites dedicated to mechanics that you mention, there are other sites that you likely have never been to that don't advise techs to rely on silver bullets. In fact we prove why trying to do that hurts them as well as the customer and the trade in general. As part of a group (Edmunds) that tries to advise consumers correctly it makes no sense to continue to promote poor habits as if they are really valid. More than 50% of what I do each day is something I've never seen before and likely won't see twice in my career. That's why problems like the fuel pump wiring harness issue mentioned wouldn't even be a note-able event. Nine months the guy fought with that problem that should have been addressed in under an hour. I do blame the perspective that having to rely on someone seeing that failure before in order to solve it is what it took. That's totally false and misleading for the consumers.

Imagine diagnosing a loss of communication between the computers on a Mazda where the chip in the transmission controller that drives the communication signal is failing and causing it to send out a pulsed wave that steps on other modules communication bits. Now also understand that the body computer also acts as the connection hub for the high speed CAN "STAR" network that this is crashing and multiple modules connect to it in ganged plugs. On that car it just so happens that the PCM shares the same plug as the transmission controller, and since the PCM has one of the termination resistors in it so disconnecting that plug shuts down the entire bus the moment that it is disconnected. On top of that, once the network shuts down the problem disappears and it then will take up to half an hour of operation for it to re-occur. That's the kinds of problems that guys like me often deal with today, and tonight I'll be demonstrating how to figure that car out to the techs that are in the class I'm teaching. Just taking the idea that the network is crashing and saying that the transmission controller needs to be replaced isn't good enough because that's what fixed that one car. As a shop you'll make yourself and your tech look foolish when that doesn't work the next time because there is a different cause for the loss of the network. That's the way a techs job really is and the silver bullet stuff needs to be put away with the points and condensers.

#Silver Bullet, #silver, #bullet, #CAN, #wallet flushing,