More car chaos

[Pixilated]

Last Saturday the 'check engine' light went on in my car. I called out for my Sunday shift as I had no idea how serious it was. On Tuesday, the light went out, of its own accord. As per normal, it flashed on for a nanosecond when I turned the key and immediately went off. I took the car in anyway, to a mechanic recommended by a coworker.

The mechanic hooked it up to an electronic scanner and said it could be one of two things (I can't remember the specifics). One would cost $400 to fix, the other $100 to fix. Of course, it could be a loose gas cap, which would cost even less than $100. So I made a second appointment so they could put it up on the hoist (mechanic's suggestion) and confirm which it was.

Second appointment: I bring the car in ... and they hook it up to the scanner again. There doesn't seem to be any paperwork at ALL from that first appointment.

And NOW they're telling me it will cost $800 to fix.

How about ... no.

I told them (truthfully) that I didn't have $800 at the moment and would have to get back to them. Then I drove to the mechanic from whom I'd bought the car. I had a fairly minor issue with him a year or more ago, but at this point I had a bigger problem with this recommended place. I'm taking the car in to Mechanic #2 next week (the light hasn't come back on).

[Arcus]

Always remember that most of the big chain auto parts stores have code readers and most (at least around me) will check the codes for free. A quick google search will give you what problem tripped it. Just don't blindly trust what google says to replace because many things can cause a code.

[Pixilated]

Always remember that most of the big chain auto parts stores have code readers and most (at least around me) will check the codes for free. A quick google search will give you what problem tripped it. Just don't blindly trust what google says to replace because many things can cause a code.

I wasn't charged for either scan. But I am quite skeptical that the first scan indicated a problem that should cost a maximum of $400, and then they decide it needs yet another scan (apparently having no record of that first one) and suddenly the cost of the repair has doubled. I mean, if I go back there in a couple of weeks, will a third scan suddenly indicate that the repair price is now $1,600?

I did see a number of things on Google that could be causing this -- ill-fitting gas cap being the most common -- but I took them as basically suggestions.

[Nunavut Pants]

Modern cars have pumps and pressure sensors that they use to check how air-tight the gas tank (including the cap) is. They pump air into the tank (or out?) and the pressure sensor sees the pressure in the tank change. If it doesn't change, or doesn't change enough, they turn on the Check Engine Light (CEL) and set a code. Assuming the code is for the evaporative emissions system or similar, the cheapest possible problem is the gas cap not sealing correctly. With lots and lots of luck, it's just not on all the way. With less luck, the seal inside it is torn or otherwise failing and the cap needs to be replaced.

If it's not the cap, it could be a bunch of different things. The tank (very unlikely unless it has rusted out), the fuel filler, the fuel lines, the evaporator system lines, the filter in that system, the pressure-testing pump, the pressure sensor .... Or the wiring that connects all of that stuff to the "brains" of the car. Just seeing the code does not always tell you which thing has the problem, though some mechanics just replace whatever the code says is wrong...