Blown PCM Fuse Causes A No-Start. But Why?

Added: 2026-06-02

[00:00:00]Gotta dodge Dakota blowing a PCM fuse.

[00:00:02]But why? Stick around, watch the video, and find out what I have to do to straighten this out. And it's not what I really wanted to do, but it's what I had to do. Here's the video.

[00:00:13]Hey everyone, how's it going? So, what am I working on now? I am working on that Dodge Dakota that I mentioned. Now, this vehicle I had worked on over a year ago, and it had a strange issue where it kept on blowing the PCM fuse. However, the PCM fuse splits out in three. It goes to the PCM. It goes to something inside. And then it goes to something else inside. I don't I don't remember what it went to. Uh the the forward control module, I think. But anyway, that's not important. So, what I did was it took a 10 amp fuse. So, what I did was I split it in three and I put 5 amp fuses in each. And all of a sudden, the car was fine. Wasn't blowing any fuses.

[00:00:49]It went over a year without blowing a fuse. Actually, I think it was a year and a half without blowing a fuse. All of a sudden, it got towed back in and it blew the PCM fuse. Okay, great.

[00:00:59]So, I double check my uh what I looked at originally and I double checked the wiring diagrams and everything else. And sure enough, that one wire from that lead goes directly to the PCM.

[00:01:09]So, let me just show you what I did.

[00:01:12]So, right here, oh, here's the car truck.

[00:01:17]>> This Dakota. So, right here, you see I split it and I got three fuses. I got PCM and I have FCM, forward control module.

[00:01:28]And then like I said, I forgot what the other one went to. The P wire must have or the tape must have fallen off or unless I just didn't mark it because I didn't really care at that point. So that fused there blew. That fuse goes directly to the PCM. So what I did the other day was I came down here and I took a look at it and I pulled it's the bottom plug here. I pulled the plug out and I ohm tested it to ground and it was grounded, dead ground. It's like, okay.

[00:01:55]Went to this side, obviously. Checked that end. Dead ground. Okay. So, it's grounded out somewhere. So, what I started doing was I grabbed the wiring harness. I can show you that. Grab the wiring harness at the back of the engine here. And I was watching the meter. And when I pulled up on the harness here, the short went away. All of a sudden, I couldn't get the short to come back at all. You notice I have the O2 sensor disconnected. I have this piece of mechanics wire here hooked to that connector down there only because otherwise it'll fall and it's kind of a real pain to get to.

[00:02:23]This covering on the harness has completely disintegrated all over the place. I'm going to try to secure the harness up a little bit. The problem is I can't get to the bottom of this harness to do an actual repair. The customer does not want to spend any money to do this. He wants to fix it as cheap as possible. The only way I could do this in all honesty and get back there is I'd have to pull the intake off. I could do it. I could pull the intake off and then I have access to the back of the wiring harness. Customer doesn't want to do it. So, I know a lot of people would say, "Oh, but you that's the way you should do it." I agree. And I absolutely do agree. The customer doesn't want to spend the money. So, what am I going to do? I'm going to do it as cheaply as possible. I spent an hour. He said, "Spend an hour to see if you can get to it." That's why I disconnected the O2 sensor to see if I could pull it up. I even disconnected the harness because the harness goes down to the transmission. I disconnected it down there to see if I could get enough to pull it up and I just can't. I can't do it. So, now we're going to basically run a wire. So, what I'm going to do is I'm going to plug that O2 sensor back in. I'm going to put this back up in the air. I'm going to plug the transmission wiring all back in. Um, I got to I basically lowered it down, too. the uh I took the crossmember bolts out, lowered that whole thing down so I could actually get in there and see if I could actually possibly get to the harness from underneath and I can't. There's just no way to do it. So, I can kind of see where it rubbed through. It rubbed through at like the very peak of the corner of the block in the transmission.

[00:03:49]I just can't get to it. Can't physically get to it. So, got to do what the customer is asking. So, let me start doing that. Let me just connect this up here and we're going to put this up in the air. I'll do everything I need to underneath and um then we'll come back up here and we're just going to run a wire and then hopefully we'll be done.

[00:04:07]Let's do it. So there you see that's connected and I have uh the that wire out, that safety wire that I used, the mechanics wire. So we're going to put this up in the air and let's connect everything underneath. Okay, so let's see what we can connect here.

[00:04:27]SS23 other side over this side. This goes here.

[00:04:37]As you can see, I pulled the harness down.

[00:04:41]Get the harness back into position.

[00:04:56]Oh, hold on. Compressor's going. Let me stop.

[00:05:01]All right.

[00:05:07]Get the right correct connectors in the right spot.

[00:05:11]Can only put them on one way. However, the O2 sensors, you can switch sides.

[00:05:15]And I've seen people do that. And when you switch sides, man, does that create a problem.

[00:05:20]Creates all sorts of drivability problems.

[00:05:27]And I've seen it happen more than once, believe it or not.

[00:05:39]Okay.

[00:05:43]Somebody put a transmission in this thing and uh they actually routed that harness on the like kind of around the wire uh around the fuel lines which it should have been under the fuel lines but no big deal. It's not really going to affect anything.

[00:06:04]All right. So there's that. And then finally, what I got to do is I got to put the I got to put the uh crossmember bolts in.

[00:06:16]Let me do that.

[00:06:23]As you can see, I got one on each side.

[00:06:58]Okay.

[00:07:01]Reason for that was, like I said, I lowered it down. But then I tried to put it back up in the air, the transmission that is, so I could get the uh so I could get to the harness, but I still couldn't get to the harness.

[00:07:32]All right. Where did I put my 18 rock?

[00:08:09]Okay.

[00:08:14]All right. So, that part of the equation is done.

[00:08:22]All right. Let's let this thing down and let's run a new wire.

[00:08:28]Had to make a short. I apologize for that. So, here we are. We're back underneath the hood.

[00:08:33]So, I just want to find out which leg of that connector there. Whoops. Let me do this.

[00:08:41]Hold on one second. All right. So, what I want to find out is which leg of this connector here where the fuse is out.

[00:08:47]Which one has power and which one is not the power? Because the one with the power is the feed. The one without the power is the one that goes to that side.

[00:08:54]So, actually, I got to turn the key on first. Let me do that.

[00:09:03]Okay, key is on. You can see the meter, right? I believe. Yes, you can.

[00:09:12]Is that better?

[00:09:16]All right. So, I have 12 volts on the first one. I have nothing on the second one. So, the second one is the feed side, which is the furthest away from the battery. So, that's the one we're going to tap into. And then we have to go to the PCM.

[00:09:31]Oops. Then we have to go to the PCM over here. And we're gonna have to splice in the wire. And just so you could see, I brought my kit with me, my kit that I made. And yes, I did find my solderless um or my non-insulated butt connectors, and they are in there instead of those other ones. Like I said, the other ones are good in a pinch, but I don't like using them if I can at all avoid it.

[00:09:52]So, let me turn the key off. I don't want to disconnect the PCM with the key off. Uh with the key on that is and this is just a functional repair.

[00:10:09]It's not a permanent repair. You can see I had taken all the connectors off before. So Just opening this up so I can get in here to the wiring.

[00:10:42]Then I got to take this outer cover off.

[00:10:48]Now, this outer cover, I don't know what you can see. What you can't see. I know.

[00:10:51]I'm sorry.

[00:10:54]This outer cover has four tabs locking it down.

[00:11:05]One, two, three, four. And you kind of have to depress those and push up on it.

[00:11:10]But I need a small screwdriver or something. Actually, I might even be able to use >> the probe from this.

[00:11:24]Or is it up?

[00:11:26]I don't think it's up. I think it's in.

[00:11:30]No, no, no. It is up. It is up. I'm sorry.

[00:11:39]Here we go. These things are probably going to break. They get really brittle.

[00:11:43]I'm just trying to lift them up slightly and they're they're breaking.

[00:11:49]Yeah, they're just they're just falling apart.

[00:11:52]You know, the same thing that happened to the insulation for the wiring.

[00:12:00]Then again, I mean, the vehicle's 20 years old. Things like that happen. What are you going to do?

[00:12:06]All right. So now what I have to do is I have to find I had already made this up when I was here last time working on it and I know that it was this wire here which is this very first wire here which is this pink wire right here.

[00:12:31]Now, what I'm going to do real quick is I am going to go look at the actual wiring diagrams again, and I'm just going to verify before I cut that open.

[00:12:40]Okay? And yes, it is the pink and gray wire. I just wanted to make sure before I go ahead and start cutting wires.

[00:12:48]Just opening up my little kit here.

[00:12:52]And what I'm going to do, I'm going to cut this up here.

[00:13:01]like that.

[00:13:08]You know what I didn't bring with me? I don't carry a lighter right now. So, I don't have a lighter on me to do the heat shrink.

[00:13:20]I'll have to see if I have one in my toolboxes. I still have my toolbox here.

[00:13:27]And as you see my non-insulated butt connectors, I'll put a link in the description for these things. These things are phenomenal, let me tell you. And this is all I use is this kind of stuff to do a repair.

[00:13:44]I don't use anything else for a permanent repair. That is if it's a temporary repair, I'll use something else.

[00:13:52]I will never use scotch locks for anything. Those things are just junk.

[00:14:05]Okay, that get a piece of heat shrink.

[00:14:17]And always try to find the smallest heat shrink you can possibly use.

[00:14:22]That's one size too small.

[00:14:35]Oh, that's the same size. Duh.

[00:14:42]It should be the right size.

[00:14:45]There we go.

[00:14:49]So, now what we're going to do is we're going to grab some wire.

[00:14:53]And do I have any thin red wire in my kit here? Yes, I do.

[00:14:58]I mean, it's thicker than what the factory used, but it's what I got.

[00:15:06]It's uh this is 18 gauge wire.

[00:15:11]That's probably um 20 gauge wire if I had to venture a guess.

[00:15:32]And whenever you're picking a a non-inssulated butt connector, make sure you pick the size that's going to work with the largest size wire you have. Because if you pick the smallest one and all a sudden you're stepping up in wire size kind of like what I'm doing here, you're going to run into a problem.

[00:15:54]Okay. So, that's it. That's perfect.

[00:15:58]What I'm doing is I'm using that jaw right there to create the crimp. So, now let me go see if I have a lighter or something that I can use on that. I'll be right back.

[00:16:09]And yes, I did have a lighter in my toolbox.

[00:16:15]Now, this heat shrink has the glue in it.

[00:16:36]So, there we go. Nice. Nice.

[00:16:39]That's all good.

[00:16:44]Be careful when you're using a lighter so you don't Richard Prior yourself.

[00:16:49]Some of you will have no idea what I'm talking about. Others will know what I'm talking about.

[00:16:56]All right, we're going to put this piece back on and then we're going to tape it.

[00:16:59]The tape will keep it in place. I'm not too worried about that.

[00:17:10]If I could find the end of the tape, I'd be happy.

[00:17:15]Let me back you up a bit. I know you're too close right now.

[00:17:33]Now, normally if like if this was my car, I would never do this. Um I would do this in a temporary situation, but I would prefer to run this correctly. I would take the intake off and do that.

[00:17:45]But like I said, you know, this is what the customer wants. The customer doesn't want to spend any money. So, I kind of got to do what the customer asks. You know, is this going to work? Like, is it going to last the life of the car? Yeah, it's going to. Is it possible another wire underneath there could wind up cutting through like wherever it's rubbing? Yeah, that's always a possibility and the customer knows that.

[00:18:04]We told them. So, but it's not my decision to make. It's the customer's decision. So, I can only do what the customer asks me to do.

[00:18:14]All right. So now what we are going to do now is we're going to run this wire across to this side.

[00:18:34]I make sure I cut enough off. I hope that way I can feed the wire in the right direction.

[00:18:48]So, what I usually try to do is I try to find like an original harness and I try to like go near it if I can, but unfortunately there's no harnesses up here. So, kind of like to go behind things if possible just to try to tuck it out of the way as much as I possibly can. I should have probably gone underneath that.

[00:19:12]Go underneath this. underneath this. And we'll try it that way.

[00:19:23]And obviously, you don't want to make it taut either.

[00:19:35]I don't know if there's a uh locking tab up here, but I don't know if it's or like a securing tab, but I think I'm going to have to zip tie to it. Let me get some zip ties. I'll be right back.

[00:19:47]I move you over here a little bit because otherwise you're going to get to see the big silverback gorilla's back the whole time.

[00:20:29]Okay, that's one.

[00:20:31]Now I move you this side.

[00:20:50]This way.

[00:21:16]Okay.

[00:21:18]So, now I come over here and try to go underneath all of this nonsense, which can be a little tricky. I'm just trying to feed it into an area where I can actually work.

[00:21:40]Hing me a little bit.

[00:21:58]Come on.

[00:22:10]All right. So, now we're on this side.

[00:22:16]So, now what we're going to do is we're going to do the same thing. We're going to cut that wire there and we're going to splice that in.

[00:22:24]So, I know it's this wire and it's this side of the fuse. So, I can take that off of there. I don't care about that anymore.

[00:22:42]Then what we're going to do is we're going to cut this as close down as we can.

[00:22:51]Now on this side, what I'm going to do is I'm actually going to No, I'm not I'm not worried about that. That's right. I'm going to leave the wire hanging open. It doesn't matter because we're not using the wire ever again. It doesn't split off and go anywhere else. It's only for this. So, I'm not concerned about it getting corroded or anything like that because it really doesn't make a difference. It truly does not.

[00:23:22]So, same thing.

[00:23:25]I hope you can see what I'm doing. Let me go get a butt connector.

[00:23:31]Uh, where' I put my butt connectors? Put them right here.

[00:23:40]Let me see if this one will fit this because this black wire is the largest wire.

[00:23:46]So, and it fits fine. Okay.

[00:23:49]And let me get a piece of heat shrink.

[00:24:05]So now see what I'm doing there. I have that.

[00:24:12]If you're if that connector that you have has a slit in it, go to the opposite side of the slit with that um dimple there that does the crushing.

[00:24:25]That's uh because if you don't, what'll happen is it'll fold over in an odd way and it may not make a good contact.

[00:24:33]or a strong contact, I should say. It could be it could actually come apart at some point.

[00:24:39]So, just something to keep in mind.

[00:24:54]And usually I try to keep the crimps on the same side. It doesn't have to be like that. That's just me how I am. That's what I do.

[00:25:24]Okay.

[00:25:26]So, now that should be all good to go.

[00:25:32]I hate these aftermarket fuses. You can't read them and the colors, you know, they're supposed to be yellow or orange or whatever. Sometimes the yellow is the orange and it's just like I I can't stand them. But what are you going to do? That's what that's what I have available to me at the moment.

[00:25:52]All right, let's uh back up a minute.

[00:26:04]All right, let's see if we pass or fail on this.

[00:26:18]Okay, I call that a win. I still have to put the airbox and that in. So, let me just do that real quick.

[00:26:29]That's why you hear that air sound.

[00:26:43]You see what I'm doing over here?

[00:26:49]There we go.

[00:26:54]didn't quite go the way I wanted it to.

[00:26:56]It popped out the grommet over here. I didn't want to do that.

[00:27:05]I didn't realize the middle bottom piece for the grommet was stuck on the screw.

[00:27:12]There we go.

[00:27:25]Let me just trim off these two zip ties.

[00:27:35]And that's about as pretty as it's going to get because I don't have anything to really attach it to over there. And it's fine considering the rest of this truck.

[00:27:50]Go a little bit back here.

[00:27:59]All right.

[00:28:02]Continue with set airbox.

[00:28:26]I was never a fan of these Dodge air boxes. I'll be honest with you.

[00:28:33]To me, they always fit hokey.

[00:28:47]the tube back in.

[00:28:49]Need an 8 mm for that and a 10 mm for the other end.

[00:29:16]That's all. All right, let's start it up again. Make sure everything's good.

[00:29:31]All right, perfect.

[00:29:35]I'm happy. Customer will be happy, too, because um we were able to fix it.

[00:29:40]Stayed within his budget. So, all right.

[00:29:43]Well, that's it. Hope you got something out of that. Um if you could hit that like button. If you could, please subscribe. Tell your friends about my channel if you could. Um really like to uh boost up my numbers as much as I possibly can, especially since I'm not really working too much anymore. All right, guys. Have a great day and keep wrenching.