CPU no.2?
 

Hi there trying to find my electrical demons in my car at them moment that have come out of the blue. I have seat belt warning light flashing and beeping randomly,,, random working of power windows and the other day i had the key warning beeper goin off all day. Studying the wiring diagram i beleive that maybe CPU no.2 is to blame anyone know where this is in the car and what it looks like because i cant find it anywhere in the service manuals?

Doesnt matter just found it,,, post can be deleted. thanks

Tiger 18,
I wouldn't delete it just yet. I think you need to change the title to reflect the problems you are having. It's threads like this where you describe a problem and hopefully wrap it up with a solution. Others might have experienced something similar and already have the answer for you...or down the road others experiencing the same problems can search and find this thread helpful in solving their problem.

My 2 cents.

Steve

ok, well ill look into my problem and pos back when i fix. I beleive the CPU no.2 has become faulty.

Just did a good search now of the forum and it turns out that CPU #2 is definatley the cause of all my quirky problems,,,ill replace and post back

I had a faulty CPU #2, but my only problem was that the car wouldn't start through the key ignition. (and I think the alarm wasn't working either). Got it switched out and cranks first turn every time.

I'll throw this photo in for future searchers.

Driver kick panel:

Attachment 711371

There are a few post with the same issue than yours (and mine actually) and they seem all related to CPU#2. Everybody's issue seems a bit different though but has the seat belt light in common for sure...

https://www.rx7club.com/3rd-generation-specific-1993-2002-16/cpu-2-function-693012/

My issue is that only the seat belt light goes awol. It goes on + beep if the seat belt is not on and it goes on and no beep of the seat belt is slotted in. The rest is fine.

I have not replaced ECU #2 yet

Good luck and let us know.

experience something similar.

if the alarm trips from CPU #2 will it keep my car turning on?

the link below is mine and have listed all everything that could be
https://www.rx7club.com/3rd-generati...start-1030102/

I have successfully repaired my CPU #2 by replacing the capacitors on the board. Very similar to the common method of repairing the speedo/odometer.
If I remember correctly, my symptoms were a constantly flashing seatbelt light, and also the factory alarm would not arm properly.

Andre was it hard to repair? and where can i source parts for it? or would any alarm shop be able to fix it?

Was easy to repair with basic soldering skills needed. You remove the case, inspect the board and write down all the specifications of the capacitors. There may be 7 or 8 different "sizes". I like to order mine from "Digikey" company on the Internet. I replaced them all even though I could only see damage to a couple of them. The capacitors are cheap so I always buy extras.

Andre, if you posted a writeup on that, it would be an instant sticky. This is a problem you see on so many FD's and so many people just cycle through these things and keep paying $20 on used ones when they could just do a simple fix it themselves.

I know I still have an extra CPU #2 at work in my toolbox that has not been repaired yet. I've also been down the used part route without success. I know that I still have the extra capacitors from when I repaired my other one. So on Monday ill try to get some photos and a list of the capacitors if that would help.

@ Andre The Giant dude that would be awesome if you can make a write up on that.
and by the way, when you opened up CPU#2, can you totally tell from a visual check that the capacitors were gone bad. or did you have to check it with some sort of multimeter???

I could see some electrolyte had leaked out a tiiiny bit on one capacitor lead/ the circuit. But since they literally cost pennies I just replaced all of them. I checked at work today and I still have all my extra capacitors, and the order sheet with part numbers. I opened up my extra CPU#2 and realized that I actually did replace all the caps already and forgot about it.
Side note: when I was first diagnosing my nonstop flashing seatbelt light, I plugged in the CPU with the case removed (bare circuit board) and went to town with my DMM attempting to trace the circuit and narrow down the failed component. Anyone with electrical experience knows this is a terrible idea, including me, but I did it anyways and ended up pulling too much current through something. It wasn't happy, whatever it was, and so in a tiny puff of smoke it burned up. I never did figure out what I damaged. But by that time I already had an extra used CPU with different symptoms so I put that one in. Moral of the story is don't try to use a multi meter to test components on a circuit board, especially while its powered up.

I totally forgot the stuff at work today so ill try to remember to bring it home tomorrow and take pictures etc...
On a positive note, I consider this repair a lot easier than re-soldering the caps on the speedometer/odometer which I've also completed.

Here's the first thread I found that helped me the most with repairing my CPU#2
https://www.rx7club.com/3rd-generation-specific-1993-2002-16/blinking-seat-belt-warning-light-fix-940893/

Remove the single screw in the center of the back cover.
Start by prying the top edge of the back cover outward.


Attachment 494245


Then pry each side to release the tabs.


Attachment 494246


The back cover should come off now by sliding it upward.
The circuit board should be loose and should come straight out the back of the case. If it is stuck, tap the case on a table and the board should fall right out. You don't want to pry on the board and crack it, or bend the pins for the connector.
Take a look at your CPU board. The components are labeled. You should inspect capacitors: C1 C2 C3 C5 C6 C7
I found leakage from C5 and C2
Note: my capacitors appear different because they are already replaced.


Attachment 494247



Attachment 494248


Here is a list of the values of the replacement capacitors I used, and my Digikey invoice with part numbers. I used all Nichicon caps of the same type for consistency.
C1: 47uF 16V
C2: 10uF 16v
C3: 220uF 16v
C5: 0.47 uF 50v
C6: 22uF 16v
C7: 3.3uF 50v



Attachment 494249


Practice de-soldering and removing the caps on some old electronics, and then practice re-installing them. The new caps must be installed without overheating them with the soldering iron.
5 out of the 6 caps are polarity sensitive positions. The capacitors have a vertical stripe on the side to designate polarity. It lines up with the printed mark on the board.
Also you can see in one image above that the new caps are folded over to a horizontal position, this is to get them to fit back into the housing. They are larger than the caps they replace.
One of the key points for success is to make sure that you solder the cap lead to BOTH SIDES of the board. There is a contact pad on the top, and the bottom, the bottoms are easier to solder than the top joints.

(More info to come later)

@ Andre

thanks for the posting up bro.:icon_tup::icon_tup::icon_tup:

Can the car be run without the #2 box in it. I did some research several years ago while the car was sitting and now I can't remember. Mine is going crazy and I just want to pull everything I possibly can out to prevent future failure.

If anyone needs them I have some good black boxes/CPU #2s :icon_tup:

Can someone please tell me the part number for the CPU #2?
I would like to get it replaced.

It is for a 2002 JDM RX7

Thanks alot:nod:

On a RHD car these are mounted horizontally and just to the right of the steering column. You can see/remove it by lying on your back in the footwell.

aka: "Package" and/or package/case footprint :)

Good thing is it's all thru-hole; SMT pad base soldering isn't as easy.

A little bump here:

On a manual transmission model, it appears that of the two plugs at the bottom of the CPU, only the right-hand one gets something plugged into it. The left-hand one does not. (Behind the guy's finger in this picture) I'm asking because I took my CPU2 out a while ago and I don't remember.

Is that correct?

Thanks,

David

Attachment 640254

Great thread! My problem was the horn would blow whenever I turned on the headlights. Plus the lamps for the driver door lock and ignition lock stopped working. Replacing the caps per this thread solved the problems.

But I have a correction. Digikey part number 493-1769-ND in the cap list for C6 is for a polarized electrolytic cap. However, Mazda used a bi-polarized (also known as non-polarized) cap for C6. Be sure to purchase a bi-polarized cap for C6. Bi-polarized costs only a few cents more than polarized.

with almost 6,3" this one cracks me up as i did this yesterday. you feel like alice in wonderland down there!

lol...yeah, try being 6'1" and uh...portly.

Looking for answers.

I am experiencing issues with my car where it doesn't want to start at all. I'm not sure if this is tied to the CPU, may be failing. I replaced my starter, bypassed the security relay and clutch switch. I also checked my ignition switch and replaced it with a working unit. The car still doesn't want to turn over. I'm not sure if the CPU is causing the car to not recognize that I am trying to start it. I also notice my windows won't go up or down. I checked all my fuses and did notice one was blown the B2 Fuse. All the other ones were fine.
NEED HELP!

I saw atkinrotary has one in stock, but before I shell out 315 dollars I would like to know what the CPU controls.
https://www.atkinsrotary.com/store/9...1-67-560B.html
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Problem solved. Main fuse was blown but had no visible damage which was weird. CPU is working fine.

Pure Gold!
 

Andre The Giant,
Great post. Been suffering from crazy seatbelt buzzer that stays on and the seat belt warning signal that flashes ALL THE TIME. Now recently I get this Click, Click at about the same rate as the flashing seat belt. What is that about? Discovered it is the "Starter Cut Relay". What does that have to do with the seat belt? Discovered the CPU #2 thread on failing caps. I changed them all and life is good. The seatbelt buzzer is on for a short time and then both the light and buzzer go off.... like when the car was new. The clicking from the Starter Cut Relay has gone away.

For sure C5 was bad with the lead eaten off at the base of the capacitor and I believe C1 had some material exiting the leads at the cap base. .

That information should be at the top of the list for "How to fix obscure problems" list.
Thanks for the info.

Mike

Yeh CPU 2 has a lot of issues and my soldering is novice at best and those things are getting pricey (one CPU 2 or one EWP kit)....so I deleted it in favor of a Programmable Logic Controller

My car developed a problem where I would hear a relay clicking at around 1Hz when the ambient temperature was cold (below 5'C).
(The indicators/hazard lights continued to function correctly. These click slightly faster than the clicking from the fault)

The clicking occured once the ignition was on, with or without starting the car. It would continue clicking for 1 min - 5 minutes
depending on how cold it was.

When the relay was clicking, the window winders would only work when the relay was on.

This forum/thread helped me resolve it, so I am adding pics and information for people with later model cars.
My car is a 2001 RB-S (manual, JDM). It has a F110 cpu 2 (BCM).

I located a faulty electrolytic capacitor by connecting the main circuit board to the loom, without the case, and then
sprayed each capacitor in turn with a little freeze spray. The problem appeared when I sprayed C4, and stopped when
I put my finger on it, heating it up.

Here is a list of the capacitors and their values -
C1 47uF 16v
C2 10uF 35v
C3 220uF 16v
C4 0.47uF 50v
C5 22uF 16v (bi-polar)
C6 3.3uF 50v
C7 33uF 16V

I replaced all except C5 (for which I sourced a spare of the wrong value).
This resolved the problem, and the BCM is functioning properly, including on cold mornings.


https://cimg1.ibsrv.net/gimg/www.rx7...c19b162feb.jpg
F110 exterior
https://cimg5.ibsrv.net/gimg/www.rx7...15f90bc29e.jpg
No bad solder joints visible
https://cimg9.ibsrv.net/gimg/www.rx7...623441d9da.jpg
No visible leakage from capacitors, or bloating
https://cimg7.ibsrv.net/gimg/www.rx7...2d44a9999b.jpg
Using freeze spray, located fault to C4
https://cimg9.ibsrv.net/gimg/www.rx7...0df3ceaf2b.jpg
After capacitor replacement
https://cimg3.ibsrv.net/gimg/www.rx7...4b329f3295.jpg
After capacitor replacement

Would love to see details of your PLC replacement.