No comm 5 volt checks out

I have a 2008 mazda speed3 and I am having issues communicating with the system. I checked 5 vokt ref on a few sensors and it checks out. I repinned the port and still not communicating. All my fuses seems to be good. While testing the obd fuse blew and I had to replace it, no issues there. So if my 5 volt ref checks out, I can here the pcm clicking, I have 12 volts everywhere I checked. Could my pcm still,be bad or am I missing something. Also trying to find the wiring diagrams as I don't have fancy tools to pull them up. Any help would be appreciated. I towed my car to the dealer because my theft lock light was rapidly flashing and I dont have a second key. Before I took it in I just assumed it wouldn't communicate because of the theft lock. Wish I had fixed this at home but the dealership has allpwed me to come take a look at the wir8jf myself. I'm already out $450. They want another 150 just to tell me what's wrong without actually fixing anything. Is it poss8ble my computer is bad or could it still be a short. I know my main battery ground is good, I also have power running to everything ive looked at. I'm at a loss rofht now. Everything I've found is referring to a bad 5 vokt ref, but what if the 5 volt ref checks out?

There can be a network issue. You're gonna want to check the ohms on the can-bus and scope it to see what's going on.

With the car off, and having been off with the key out of the ignition for at least a minute or two, take a multimeter on the resistance setting and put the leads in pins 6 and 14 on the OBD port. It should read about 60 ohms if the CAN network is operating normally. Anything much different than ~60 ohms indicates something wrong with the network.

Are you using a global OBD scanner, or one that can communicate with other modules on the network?

Just a standard obd2 reader, one of those single line led screens. I talked to a few mechanics, one suggested that I may have a short in pcm ground or battery to block. I'll be going back to double check a few things tomorrow and I will follow your advice. I'm still fairly new to the electrical side of automotive repair so this is turning out to be a huge learning experience. I know I have power to the pcm, I can hear a rapid click, which is what made the mechanic I spoke to think it's a ground issue. I have 12v power to the port but I have zero voltage on the comm line,to the port. I finally got my hands on a wirinf diagram so that should help me figure out what wires are my grounds to pcm. The mechanic said he believes the can bus ground is separate from the 5 volt ref. I am going to replace the negative cable and fuse box positive, last year I had to replace my positive cable to the starter because it had shorted out. The positive to fuse box is barely long enough to reach the post clamp, it's basically under tension so it needs to be replaced anyways. I'll check tye back side of my fuse box. The previous owner removed the engine balancer for increased oil capicity, pretty typical to,see done on a speed3, so it,definitely has a lot of vibration in the engine bay. I know I'm rambling but I'm trying to consider all options.

First off what exactly does "repinned the port" mean? And why was it done? Also have you connected your code reader to this vehicle successfully in the past? If it's an older one it might not be CAN capable.

PCM powers & grounds, or shorted 5V, could take the PCM offline but shouldn't take down the entire network. Did the dealer say whether they couldn't communicate with anything on the HS CAN or just the PCM?

Sorry for the misunderstanding. Sports Cars like mine wont run without tuning so we use a Cobb tuner to run orgrams and gauges from the obd2 port, dlc. After a while the pins can become loose. So you take the wires out of the back and put new pins on or tighten the connection down. They were definitely pretty loose. I reinstalled the pins and now the scanner fits in tight to the point its hard to disconnect it. I was hoping that would fix it. Did nothing.

No there is zero communication. He said the fathest he got was checjing the fuses and establishing there is power to the scan port but no communication whatsoever, ref voltage was good everywhere I checked it. Leads me to believe there is a ground short on the pcm or to the battery itself. When I was there I didnt consider a main battery ground short, it could make sense. I didn't load test it. I could even be losing power from a bad positive to fuse box.

I'm going to go by first thing in the morning and check the wires I mentioned and do the ohm test that was reccomended in an earlier comment.

A couple years ago I replaced the starter because I had power everywhere in the system. I jad the fan, lights, stereo running and everything worked, the positive battery cable had a short in a fusible link. So small you Couldn't see the break in it. Point is I know that as strange as it seems a bad battery positive or battery ground issue can cause all sorts of problems. The fact I have had the battery in and out of that car as many times as I have, and the fact I have high vibration makes me really think ite a shorted ground. I meber did test body ground, just block ground, the system very well could be a body ground. If my scan tool,powers up I can probably assume I have a good ground on the port but that grounds out separate from the pcm. Please understand I have a $50 multimeter and a $30 scan tool and a couple test lights. Nothing fancy. After hours of searching I finally found an online wiring diagram, I wasn't about to pay $200 for the book. Everything about a sports car is expensive so I have to save money where I can. Im still learning the electrical side of things so I apologize if I am not being clear.

www.eautorepair.net for your wiring diagrams which is significantly less for your diagrams.

Awesome I'll check the link out, that will help a lot, the diagrams I did find aren't very readable on a phone so I'll check those out. I wasn't abke to spend a whole lot of time on it today. Basically just rewired the negative battery cable since it was looking orettt bad, it did jot help. Iwanted to apply a heavy load to the system so I used a jumped wire on the starter relay. The entire electrical system went haywire. It turned my a.c. on high, turned the cooling fan on amd I could here vlclicking in multiple locations throughout the engine bay. The positive wire is very stiff so I am wondering if there might be an issie there as well. I woke up much later than I leant to so 8 was only there maybe 30 minutes, most of which was s9ennt taking the 5 miles of electrical tape of the wires so I could get the negative cable out. While I was in there I noticed everything 9s s9aked in break fluid and I have a minor break in my clutch brake line, so maybe that has something to do with it as well, I'll go back in the morning and retest the can bus and see if I have continuity. I still think there has to be a major short for my car to act the way it did when I tried jump starting it from the relay.

Also despite a theft deterrent lock on the system I can hear the fuel pump operating which I thought was supposed to be shut down by the theft deterrent. Idk. My check engine light is on om the dash so it makes me think the pcm is operating. Again the pcm itself has a very rqpid clicking comeing from it. Probably about 6 clicks over second and every few seconds there is a pause for about half a second then it starts the process over. I have a humming sound coming from my throttle body but even with the sensors unplugged it doesnt change the communication issue.

If I don't have continuity at the port for can, whay would that mean? Sorry if I'm rambling.