Hey all,
About a month ago, I got a 2005 Mazda 3 Hatchback. The Check engine light has gone off in total about4 times. Once, there was actually a problem(maybe the emission control valve or something?). The other times, it was a fluke and there was no code recorded. So anyway, I thought those problem was solved last Friday because the dealership rebooted the "black box" that controls those codes, but the CEL went on again yesterday. According to them, the next step would be to replace that black box. So here are some questions:
1) Is the "black box"(not sure of it's technical name) definitely causing the CEL to go off for no reason? I'm afriad that this is a problem intrinsic to the car that will not go away. I'm worried that even if the black box was replaced, the CEL will continue to go off. Essentially, I'm afraid the car's a lemon.
2) The dealership said that I shouldn't go to an auto repair shop to have them read the code because they can delete it etc. Is this good advice? Right now, I am 70 miles away from a mazda dealership, and I'd like to be able to know what's wrong without having to drive all that way(I won't be able to make it to the dealership for at least a week).
3) How long will it take to replace the black box? Do you think that it could happen while I wait if I arrange it with them beforehand? I'd like to, as the dealership is so far away from me.
4) Should I be concerned about driving with the CEL on(for perhaps even a month or so)? Assuming it is driving normally, etc.


Thanks a lot
Matt

 

Matt,
I am taking my '04 in for the second time in a week tomorrow for the same issue.
The "black box" is generally known asthe ECU (Electronic Control Unit,) but Mazda seems to call it a PCM (Programmable Control Module,) and it should only take minutes to replace, unless they have to re-flash it, which I'm told could take 1.5hrs to download the new software into it.

After mine was in overnight from Monday to Tuesday, the CEL came on after only 25.2 miles of driving and I'm only a little better now than I was then. The car does run better now than before, but the light is driving me crazy.

I will write back after I get home again tomorrow and let you know the short-term outcome.

 

Of course the dealer does not want you to go to an auto repair shop that is not them - they do not want to lose your business!

As is indicated in the article below, some auto parts stores will read and interpret the code at no charge. If I was experiencing frustration with the dealer, that is whatI would do.

http://www.consumerreports.org/cro/c...1205/overview/

What I know works is, disconnect the battery for five minutes, then reconnect it. This will reset your CEL (turn it off), and may even reset your ECU (I have heard the ECU resets itself if it is disconnected from the battery for more than a couple of minutes). If the problem is real (or your ECU is wonky), the light will come back on. It's not like you'll lose anything.

 

i have that same problem! i first noticed it yesterday that my check engine light came on. My dad suggested that the gas cap might have been loose and after attempting that the CEL was still on. ANY SUGGESTIONS???

 

Reset the codes with either a reader (borrow from a local auto parts store) or disconnect the battery as directed above. Once the code is tripped, the light will stay on until reset. (This helps in catching intermittent issues that come/go, the code would be saved to indicate what was working wrong.)

 

I have had the same problem with my car Mazda 3 2005 about 2months ago my car started acting funny
so I brought it in to the dealership and they cound not find the problem so far my car has been in 6 times and still is not fixed

 

One thing I'm sure of and that's that the MAFsensors on these (same one as used on some Toyota's) are very sensitive. It may simply be dirty as they do get that way over time. You might try carefully removing and cleaning it w/rubbing alcohol.TREAT IT LIKE YOU WOULD AN EGG, not roughly!! Reset the PCM/ECU by disconnecting the battery for 10-30 mins, reinstall the MAF and that just might take care of it.
After my second trip to the dealer they discovered that the NEW MAF they installed was faulty and replaced it again!!
So the outcome of my problem was 2 fold: 1) Reflash the PCM/ECU w/the latest software. And 2) replace the faulty MAF sensor. After 2-1/2 months and 1500 miles, so far so good.

 

Does not sound promising that the ECU fails. Is this something common to '05 or is it a chronic Mazda issue?

 

Not the ECU.That can be (easily) updated w/new software byany dealer. The MAF sensors are sensitive to dirt and rough handling. They need to be cleaned very carefully so as not to damage the sensor itself.