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sachipahath

Mazda Bj5 Ecu Problem

Question

guys i am having continues problems with my bj5 ecu. the main one is that the unstable rpm meter. some times the rpm goes up & down when its idling. pls help me to resolve this.do i have to replace the ecu? where can i find one? and my car is a 1.6cc manual.



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How are you sure that the problem is with the ECU? An erratic RPM could be due to other reasons such as a failing Idle Air Control valve.

Edit: Didn't see that your question was answered in the duplicate thread. Hope mods will merge threads.

Edited by Davy

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Guys,

I will be taking over this thread to discuss an issue with my brothers Mazda BJ5W triptronic VVTi engine. Few weeks back he had experienced a sudden engine shut down while he was driving (from panadura to Townhall). few seconds after when he cranked the engine it had started again and had been running smoothly for few days.

Then again about two weeks back, car suddenly stopped near Mt lavinia area after a drop in the RPM (no matter how hard you accelerate RPM doesnt go beyond 1500-2000 or so) and the car stopped with a vibration. Then again after few minutes it became normal. But this time we took it to a mechanic but the issue was not there at the time it was taken to the mechanic. Mechanic also had a test drive, did a scan but nothing came up. However mechanic observed that there's a oil leak from the engine and he assumed it might be due this oil leak that the crank sensor has been malfunctioning.

So we replaced the crank oil seal and tapered covers, also fix a new crank sensor and started running again.

After few days running (two days to be precise) the issue came again. Same way the car stopped after dropping in the RPM and vibration. This time since I was also there at the car I told my brother not to take the key out but keep cranking the engine and if the engine start again keep running with the problem until i get a mechanic. So we were successful and i managed to get a mechanic with a scanner while the issue was there and after the scan attached error report was produced.

https://www.flickr.com/photos/[email protected]/27332286162/in/dateposted-public/

https://www.flickr.com/photos/[email protected]/27332286262/in/dateposted-public/

Then again the CAM sensor was replaced but the issue was still there. Later the Air flow sensor was replaced (After replacing the old CAM Sensor). However non of the above has been successful.

Can the experts here assist me to overcome this issue as we are clueless of what else to do.

Regards,

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Was the car subjected to recent flood waters? Because when I look at the diagnosis report, it looks like some kind of loose connection/leak in electrical wiring/connectors/fuse because the car has produced errors in almost all the sensors which are seemingly unrelated.

With the engine running try to emulate the fault by shaking the wire harness inside the engine bay and under the dashboard. If you fail to find a clue, check the electrical connections beginning with the battery terminals. Remove the fuses, plugin type relays and visually check them for discoloration, cracks, dirty contacts etc. There are several grounding connections on the engine block. Check if they are loose or corroded. Check for loose connectors particularly those under the hood and the one at the ECU. I do not think focusing on the things indicated in diagnosis report will help you to home in on the actual issue. Could be a problem with ECU but first we need to eliminate other possibilities.

Edited by Rumesh88
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Somebody has stolen a Sampath bank POS machine paper roll :P

Edited by NRX

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Somebody has stolen a Sampath bank POS machine paper roll :P

No. scanned by a Sampath POS machine.

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These could be very old faults as well, clear the codes and run for about week and see. The cam position sensor and engine knock sensor failures are common in all bjs.

Like Ramesh has suggested it's very odd for all the sensors to fail, were there any electrical issues in the car before? It seems like all the sensors are fried. If you can find someone with a good electronic background and check the voltages to the sensors from the ecu

Edited by The Stig

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Hi guys, thanks for your responses. Rumesh thank you again for extending your helping hand. Car was not subjected to floods rumesh. I shall PM you some details. Highly appreciate if you can reply.

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Rumesh I tried messaging you but couldn't get through. Is there a good place we can take the car to have a look at all what u have said. Cos I don't think the current mechanic has a clue of what's going on.

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I too have a BJ5W car with ZL-VE SVT engine (manual transmission).I too faced the similar situation approximately six months back. Ran to few mechanics from whom i got false diagnosis, decided to do it on my own. After a few trial and error, found out that two out of four ignition coils were faulty. M***A asked 27k for a recon set. However, managed to find em brand new(genuine) from Panchi (D*h*n*y*k* ) for 15k. In my case, I suspect the cold weather during December, and parking the car under a broken roof gutter caused this, So, check your ignition coils as well. Just my 2 cents.

Edited by similarnames
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hi guys,

Just returned from the mechanic. We brought the car home from there as the issue has never been come up when it was there. However after we brought it to my office, I observed that when it is pedaled gradually (say from initial RPM to 3000, gradually pedaling so that RPM also raises gradually), RPM indicator shakes while it is raising. and during certain intervals it suddenly drops (say about 1000 RPM drop). I have been repeating the same thing over and over 3 or 4 times and the RPM started dropping continuously until it no longer raise and the engine stopped.

Now my brother is getting ready to take the car to M*z*na. I hope it wont give trouble while going in the heavy traffic in Nugegoda, kohuwala area.

Regards,

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I've been running a BJ5P with a ZL-VE SVT engine for more than 7 years now. About 4 years ago something similar happend to me

and the reason was a busted ignition coil. Replacing it solved the issue at that time but after two weeks

same issue occuered again and the diagnosis was that the second ignition coil pack has followed the fate of the other. :-) So, had to

replace it as well. Since then had no issues and the car has been running smoothly without any issues (for nearly 4 years now).

Therefore i suspect you might have faced the same issue. So, how about checking the ignition coils as mentioned by 'similarnames' as well?

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