Hi all, first time poster in need of some input.

I own a 2005 Mazda 3, 2.3L Automatic, purchased used about 4 months ago. It's currently in the shop, and after three days of diagnosis the mechanic wants to replace the computer for a total of $600 (~$300 for the computer itself).

Here's the background info on the problem I'm having with the car. The car has run great since I got it. The Check Engine Light has been on since two weeks after the purchase; the diagnostic test revealed only a O2 sensor, and the mechanic recommended that I don't worry about it. So the light has remained on, and I have not had the O2 sensor replaced. The car ran great up until last weekend. I drove to my destination without any problems. When I got in the car to return home, the AT light came on and the car would only rev to ~2,000RPM. (It did not red-line at 2000, it simply stopped stayed steady at 2000). I checked the transmission fluid, there was only about 1/4 inch on the bottom of the stick, so I added some. Didn't solve the problem, but I drove it home since I was pretty close. It would only go about 20-30mph, shifting when it picked up enough speed. One of my friends recommended I reset the computer, so I did. The AT light did not come back on, however the problem persisted. I'm fairly optimistic it's not a mechanical problem with the transmission. I have never experienced any problems shifting or accelerating, and again, it seemed to run perfectly fine until this problem suddenly occurred.

I took it to the mechanic on Monday. He said he got a code from the computer for the Mass Airflow Sensor. They replaced it but it didn't solve the problem, so they removed it. At that time, the mechanic told me that he was concerned about the computer, since it appeared to be a "salvage" computer and appeared to have water damage. The carfax for the car is clean, fwiw, however the previous owner did make a few minor modifications, though I don't know why he would have replaced the computer.

At that point, with no other codes being registered by the computer, they started a 3 day diagnostic process testing the sensors and the wiring and connections. Throughout the process at various times, the computer registered several codes for various things from the transmission to engine problems, though the codes came and went. Also, the computer didn't register information or codes that it should have throughout the process.

For this reason, the mechanic said he was "as certain as [he] could be" that the computer needs replacing, for the price quoted above. I don't disagree with him, however I fear that the computer is not what is causing the problem above, but simply a means of correctly displaying the cause of the problem above. So that adds up to $600 for the computer, + $xxx for the real problem. I can afford one or the other, but not both.

So to save money, I want to know if it's reasonable for me to be able to purchase and replace the computer myself. I have a few questions about it, though.

-I only have the model number of the computer CURRENTLY in the car, which apparently is not the ORIGINAL computer. Can I purchase ANY 2005 Mazda 3 2.3L Automatic computer?

-Will the computer require programming before it will work? Or is it essentially plug-and-play?

-What is involved in properly replacing the computer? Is it correct that it is beneath the battery?

FWIW, I'm currently looking at this computer:
http://cgi.ebay.com/ebaymotors/ECU-E...ht_2213wt_1118

Thanks a lot for reading. I posted the full situation incase someone has some input on not only replacing the computer, but any other possible causes of the problem. Thanks in advance for any information.

 

Ill start by answering your questions

-If you do you have to make sure that the options match what you have, like abs traction control

-Yes it will require reprogramming, parameter reset, immobilizer reset among other things

-Yes it is under the battery, just a few bolts that hold everything down and pull the wires to the ecu

Given the problems i can see why he would say that, he may be on the right track, seeing how as the transmission and engine controls are in the same ecu, but ive got a few questions. Carfax says that the car is clean but it only knows what its told, previous owner could of had work done under the table, what are road conditions in your area, does the ecu model # match the vin (only a dealer would know). A number of things can cause the problem (i dont know what tests hes really done) it can be from a loose or corroded terminal(s), with the absurd amount of engine movement for the sake of no cabin vibrations and seeing how its an 05 there might be broken wire(s) anywhere along the harness (hopefully hes rules most of this out during his tests) working at a dealership, replacing the ecu is a last resort, and during my training its been known to not fix the problem. I hope for your sake you took it to the right guy but a diag resulting in needing a new ecu is not out of the question

 

So...My car is 2003 Mazda 6 3.0L V6 S (AT).I have problem with ECU,ECU number is "ECU PCM Brain Computer Engine BDD3 AJ58 18881 G 3.0L V6 S ECM".The thing is that Ecu's one of the cheap/micro scheme burned,and because of this one of the cylindrs stopped working(but car is still running).My question is next:Is there any difference and if it is what difference is between 2.3L ECU's cheap and V6 3.0L cheap???Can I use 2.3L ecu cheap for V6 3.0L???
SORRY FOR MY BAD ENGLISH I HOPE YOU CATCH WHAT I SAID

 

I really wouldn't think so. PCM's are usually very specific to a certain vehicle with a certain engine. With the Mazda PCM's being "untunable" I don't know that anyone could crack the code to install information relevant to your vehicle?

 

The only thing I can add is that Hypertech can add a power program (update) to the ECU of the 4 cylinder, but they can't do it to the 6 cylinder. The 4 cylinder may be reprogrammable, the 6 cylinder is not (requires a piggy back tuner).

 

Lol this is ironic to my post. JET can tune our mazda3's/6's ECU's. If you buy one off of ebay like I did, make sure every visible number matches. the PCM's are NOT compatible even 1 letter or number off will render your car inoperable. Once you get it, The dealer will need to flash your VIN number into the PCM as well as probably flash program it. You will need to bring all your keys with you as they will have to flash your keys codes in the the PCM as well. My Dealer charged me $65 for the keys and $125 programming the VIN so $190 total. you can by an Ebay PCM for what $200? $390 total Vs. $600

Your dealership might be able to look up your VIN number and tell you exactly which computer to get. IDK why or how someone put a v6 mazda6 computer into a 2.3L mazda3.

 

Hi there,
I know this is an old thread, but just wondering what happened in the end? Did you get the PCM replaced?

I'm having a similar issue with my Mazda 2, don't want to fork out $3000 unnecessarily, but not sure what my options are...

 

Hello there, hey its easy to replace the EC, I have a 2007 Mazda3 hatchback n mine is under the battery, it only take about 20 minutes to do, plus I bought my ECM for only $80 with warranty, you should google your car n it will show you how to do it, plus to get the correct ECM for your car call a Mazda dealer and give them the last 8 numbers or letters from your cars Vin #, let me know if this helped or if u need help locating an ECM, hope u get it going.

 

This may be a late response, but i own a 2015 Mazda 6 and was searching for a way to reset these CPU or ECU whatever and came across your issue. I owned a Ford Taurus 2016 a few years back and had a bad 02 sensor, and ignoring it was there worst thing i ever did. In case you are unaware, the 02 sensor tells the CPU how rich or lean to regulate the fuel. To sum it up, my faulty 02 sensor was telling my cpu to run to rich or lean fuel. What that did was burned up my catalytic convertor. I was driving home one night on the freeway, and had a complete loss of power while driving. Engine was still on, just no power no matter how hard i pushed the gas peddle. Engine was Screaming, but no energy. My car was slowing down. Long snd short of it, the fuel mixture that my faulty 02 sensor was sending to my CPU was to rich. Burned up my catalytic converter. No exhaust flow was getting past the CAT next to my manifold. When i found a spot to pull over, my CAT was glowing red. It was all downhill from there. I shared my story cause it sounded similar with loss of RPM , and a bad 02 sensor. If it helps, cool. Pay it forward. One last thing. After i pulled off the freeway. I too, could only drive sty snot there fastest was 15 mph.

 

The problem your having sounds similar to the problem I was having with my Mitsubishi Ellipse. My timing belt went out so I had someone fix it... shortly after that I couldn't go any faster than about 40mph (unless I was going down a step hill) I was told by many what it could be but I was convinced it was something to do with the timing belt.
. Anyways to make a long story short, I took the timing belt cover off and it was shredded. It actually has two and the guy only replaced one. So it still ran, kinda, if you want to call 40 mph running??
In doing the timing belt I also discovered the Cadillac converter had a hole in it. I did both then it ran great. I'm not sure if it was just one or the other that was the problem or both? But maybe just check both?
Hope this helps. It just sounded similar and nobody told me to check those, I just had a feeling and that feeling solved my problem.