Recently I had my "Check Engine Soon" light come on in my car. I noticed that the car was idling low when I would first start it up in the morning, and over the next few weeks the issue got worse until it would idle so low that it stalled. However it would crank up again and would run fine for the rest of the day. Since I was getting ready to take an in state road trip, I decided to go ahead and have it looked out before heading out. The mechanic that I took it to (not one that I was familiar with at all) told me that the code that was given when he read it, was for the "fuel system". When I asked what that meant, he told me it could be a number of things and that they would just have to investigate the components until they found the issue. The next day they called and said that it needed a mass air flow sensor and some cam sensors. So these were replaced and the car seemed to be running better and the check engine light went off.
On Monday, while driving back from a friend’s house the light came on again (although I had not had any stalling issues as before). I took it to an auto-parts store to have the code read, and the particular one I went to told me that they did not do that because they had no way of actually being able to break down the general code and that my best bet would be to take it to a mechanic and have it read. So, since I was in my home town, I took it to my regular mechanic and he read the code and said it was a catalyst code. I explained to him what had happened two weeks prior and he told me that there were more specific codes that just one that said "fuel system", which seemed to align with what the guy at the auto-parts store had told me.
So, I ask, are there two different types of instruments for reading these check engine codes? For example is there one that is possibly a cheaper type that only is capable of reading general codes, and one that is a more expensive instrument that is not only capable of reading those general codes but also capable of going beyond such codes to specifically tell you that it is an issue with the mass air flow controller or the thermostat, etc.? Because it seems from what I was told by both the guy at O’Riely and my regular mechanic this is the case. He told me that his instrument could have called the fuel system main code and then called sub codes for the mass air flow controller and cam sensors.
My mechanic did clear the code and told me to go ahead and drive it and see if it came back on, just to make sure that it was not a fluke, but that if it does come back on that we would need to investigate why it was throwing a code for the catalyst components. I spent close to 900 bucks on the previous repair of the mass air flow sensor and cam sensor, so is it possible that since these guys at the shop that I had never worked with before, did not have the proper instrument to check my code and therefore replaced parts that really did not need to be replaced, when instead it was an issue with the cat instead? Would an issue with the cat components fall under a general code for the fuel system?
Also in the event that there was actually no need to replace those sensors, does anyone have some thoughts on how to proceed with possibly getting some type of refund or compensation from the people who did the original work two weeks ago?
I know this is lengthy, but just wanted to make sure to get as much of the background info out there as possible.
Thanks in advance for you thoughts, input and assistance!
2001
Nissan
Sentra (Base Model)
Steve: I am not sure that you grasped my question as your response addresses none of the questions and points that I posed. One being are there different types of code readers, could a cat code be encompassed under a general fuel system code and lastly, is it possible that the issue was actually with the cat in the first place, and by replacing the mass air flow sensor and cam sensor, all that was accomplished was a temporary "patch" instead of actually adressing and correcting the root cause to the problem. Being a doctor and a scientist I use logic everyday, especially when I am working on an Mass Spectrometer worth over a quarter of a million dollars….and from that mechanical experience I have learned that different instruments have different fault log types (which would be similar to the error codes that are thrown by car computers). Some models have fault logs that are very specific and some do not, which is why I posed the question about different code readers.
J M: First off, thank you for answering my main question regarding the difference in code reading instrumentation. That was the part that was somewhat confusing to me, as the first mechanic was telling me that the only information he was able to obtain was that the error code had to do with the fuel system and that was it. Whereas the second mechanic (which mind you is a more specialized and larger business) told me that his code reading instrument could detect specific faults that branch off of the general error code.
The reason I am wondering if I have a claim with the first mechanic is because he told me that there was no way for him to pull a specific fault (even after I asked him this point blank). So, instead they just fiddled around with it for days, and in fact the first day, they actually made the car worse. So, my issue is, that since he did not have the more specific code analyzer, who is to say that he did not replace the wrong parts?
EDIT: Also just to clarify, I have not had a new cat put on the car, as I just swung by my normal mechanic to see what the code was, and he said it was indicating that it was something to do with the cat. He cleared the code and wanted me to drive it and see if it popped up again to make sure it wasnt a fluke.
Basically, if the initial mechanic had told me the truth, that he did not have the instrument which measured the specific faults, then I would have taken the car somewhere else to begin with, end of story. Also while it was there I told them I had an oil leak, and they charged me for fixing it, yet my normal mechanic told me that I still had an oil leak. So putting all of this info together, makes me question the quality of troubleshooting on the part of the first mechanic, therefore, I simply am trying to find out if it is possible that the parts they replaced just patched the problem, basically just compensating for an issue with the cat.