ECU (fried?)
 

I didn't see a thread on this, but here is my questions, I was having issues with my display along with the radio, so I was reading thru threads to see what I could do and one of the threads said I should replace the battery so I did, now the bad thing is I put an optima yellow top in my car, but the old battery and the new battery were different, the positive and negative where switched, so I put on the terminals like I had the old battery and my car went crazy, I thought it was the viper car alarm system so I had a guy come out and check, and he said I switched the terminals and put them on backwards, I told him that I didn't know battery's switched like that, but long start short he said I could of blew my ECU so I went and got a new battery that fit with the terminals now, and the car won't start, I get power, but it won't turn over, so I bought a OBD2 and hooked it up and it's saying it won't connect to the car, I tried it on my Mazda 6 and it connected to the car, so my questions are is it the ECU? I replaced all fuses already and if it is the ECU where can I get one for a M/T?

First, start checking every fuse and relay. There are two banks of them, one in the driver's footwell kick panel and the other in the engine bay just behind the driver's side headlight.
Validate that all fuses and relays are good, nothing melted.

Next, have your starter tested OFF the car.

If they are all good then yes, you most likely fried your PCM (ECU). Expect a huge bill if you have a dealer replace it. If you manage to find one somewhere else, make sure it's the right part number for your specific trim/transmission/etc... You will still need the dealer to sync it up with the rest of the modules properly.

Also possible you damaged one or more of the other electronic modules in the car.


I recommend paying attention to battery terminal markings in the future.

Thank you, how can you tell if the relays are bad? Most of them are black and you can't look through them to see if they have blown, I was going to replace all of them but some cost like $20.00 or so and I think I have 8 to 10 of them

Also the only fuses that got blown were the 15a engine and the interior audio fuse

Get a multi-meter and test the continuity between relay prongs. You are going to have to do some research on what you need to be looking for on each relay. If you know the 12v side of a relay, you can also test that with the car battery to make sure it functions properly.

Replace those two fuses before digging into anything else. The engine fuse itself will prevent you from starting, and may be your entire problem.

That couple cent fuse may have saved you several thousand bucks.

dont forget about the mains fuse, 120A and underneath the mains harness at the fuse box ... easily missed.

I already replaced the fuses, I took all of them out and put new ones in just in case

And I followed that harness but didn't see the fuse do I have to disconnect the harness or take off the fuse box to get to it?

#1.

http://wiringcircuitdiagram.wiringdi...el-Diagram.png

I seen that but where number one is, is a harness connector, I didn't see a fuse it goes kinda up under the box itself

check this post out.

https://www.rx8club.com/rx-8-discuss...5/#post3036990

Yes that helps a lot thank, sorry I'm new on here and I did search for ecu but didn't find anything next time I will search everything going to see if I can find anything on relays

if the car has power then the 120A fuse is fine.

with the engine fuse replaced the car still does the same thing? does it crank at all? "turn over" means different things to different people.

Yea, I get power to the dash, but no power anywhere else except headlights and windshield wipers, won't crank at all, I reset my car alarm that still works, but I can't roll any windows down, sun roof, locks, heated seats anything and when I hook up my OBD2 it doesn't connect to the car at all

check the BTN fuse specifically and also the starter motor as described by RIWWP. i would also check the engine fuse again.

(i realize you already replaced all the fuses but a short caused by the reversed battery may be blowing the new fuses)

True I'm going to check the main fuse and see if it is blown and go from there I will keep you guys updated

Well if you are having a can bus issue and the fuses are good then you have serious issues. You need to get it properly diagnosed by a qualified technician.

before we assume that, he mentioned it wouldn't connect at all. i don't recall which fuse powers the datalink connector but if it isn't powering up the scanner then it doesn't necessarily mean there is an issue with the BUS or ECU.

since nothing works inside the car the datalink issue might be first on the list to go after. normally the cigar lighter fuse powers the datalink also but don't quote me on it in this case. i would simply check all the new fuses again.

my mistake, missed the part where you were getting some power to the vehicle.

Is the "engine " small fuse good?
What lights up in the dash.
Got a feeling this is going to be a real puzzle......hope not though.
Can bus issues in these cars are a black art.

they are on most every car, it's actually almost cheaper to just keep replacing modules until you find the one that is scrambling the data than to try and decipher the stream and figure out where the root failure is.

but module failures are relatively uncommon, i'm betting it's just a short somewhere that keeps popping fuses. which even that can turn into a nightmare quite quickly.

This is not a computer issue, check to see if power is available to your foot well fuse box. Also recheck the fuses down there. If no power is available then check at the main fuse box, it's probably the accessory fuse, but I'm too lazy to look it up. Somehow you are missing a substantial amount of power to accessories and when you fix that, everything else might work too.

you got the wrong battery. I had redtop and now Yellow top. what reversed terminal. I'm so surprised that people can be so retarded and get the wrong battery.seriously wtf ?

check everything and hope for the best.

thank you

for those who cant read, it means do NOT believe whatever the parts guy(nor their computers) tells u, lots of time they are wrong. u got the wrong battery cuz it probably told u a 24r or 34r will work, its wrong. most if not all japanese cars uses group 35 size battery.

another example is, when i tried to fix my 1991 fc that has a broken condenser for god knows how long, got most parts and needs a new drier(for those who dunno, drier on rx8 is part of the condenser assembly not a separated part), checked all local az/aap/etc, they listed the wrong drier, first i told the parts guy its wrong, the parts guy looked at me like i know nothing and assures me that its right, just to embarrass the shit out of him i told him to go ahead and order it. couple days later the part came, its wrong obviously, i took my old drier there and said "what part of this drier is the same as the drier u said is right? " he act stupid and was like no way hose. i told him exact what to order and another couple days later the right part came.

/storyends

so yep, do ur own research b4 ur buy ur next part