This issue has been bugging me for a week and I'm stumped

This issue has been bugging me for a week and I'm stumped.

I have checked the voltage and ampage on the battery, it is good. I have replaced the alternator through warranty for a new one even when the last one tested good and I have cleaned the battery terminals real good. I've checked all fuses and relays and they are good. Checked the starter wires and they are good and tight. SJB is dry as the desert and so is the carpet around it.

What is happening is the computer seems to reset itself when any kind of electrical stuff is being used. Even when I open the doors and the window automatically comes down an inch or so. It doesn't start period now and no power appears to come on EXCEPT the flashing anti theft light right now. Before, no power came on period. Everytime I try to crank the car with the key, it either does nothing at all or I hear that sound the instrument cluster makes when you reset the ECU.

Yesterday, it worked just fine. I drove it for a couple miles with no gremlins and started it up and off a dozen times. Then I park in the garage, close the doors and hit the lock on my key fod and bam, all power goes out. I try disconnecting my battery and instead of my alarm going off when I connect the negative terminal, it clicks nonstop as if it's trying to off but can't.

This all happened last friday when I was parked, driving home from work and out of nowhere the car's computer started resetting itself while the car was driving but the actual motor wasn't turning off. I made it just far enough home in my driveway then the car wouldn't turn back on again until tomorrow when I disconnected the battery and let it sit for a couple hours. The day after, the motor was turning off while the same symptoms were showing though. All dummy lights like ABS, TCS go on, gauges reset, radio resets, lights turn off and on and you get that braking feeling.

video is second post

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Here is a video of what it is doing right now, and you can clearly hear the noises and computer clicking. One of the clicks is me constantly turning on the lights which causes the computer to reset ( or the use of any electrics it appears ).

How do I go on about finding the problem? I'd hate to take it to a mechanic and get charged an arm and a leg.
Car in question is a 2006 Mustang GT. Tuned but ran fine for 11k miles since the tune until now.

no one?



I would try an ECU that is known to be working.

fuck me, those are like $400. My shit only has 115k miles, what would cause it to go bad? One day it ran like a champ then the next it took a massive shit.

I think it's totally fucking fucked mate, big time

What car.

If everything is fine but the ECU resets each time something electrical is being turned on it might mean there's something adding extra resistance or there's an electric leak somewhere. Overall i think that all this shit of having the ECU link with everything in the care makes it way more expensive to fix and a bitch to do so.

old age and duty cycles can make some electronic components (like relays, capacitors, transistors) in ECU go bad (or out of tolerance).

since you claim that you have properly checked the electrical system and its all good, one would suspect ECU - or any other electronic control unit for that matter, might have gone wrong.

also disconnecting any third party electronics might help with troubleshooting.

Symptom is consistent with a bad connection.

As an example, a friend had a 1990 Mustang LX 5.0 and when it was a year or so old it developed a similar thing where it would occasionally clear the clock and radio presets. Battery checked out fine, starter ran at good speed, amperage draw on starting was in the normal range. After putting up with it for some time he decided to get more in depth with diagnosing it and eventually found that the negative battery cable connection to the timing cover on the engine was just ever so slightly loose and you could move the cable end under the bolt with some decent effort. Tweaked the bolt down to where you couldn't move cable end any more and no more problems. IIRC what put him onto it was the voltage between the battery ground and engine was like .2 volts cranking instead of less than .1. Really subtle and most techs would never find that until it got a lot worse.

Fuck man, there are over 50 grounds all over the car. Where the fuck do I start? What is a bad ground? They ALL have a bit of surface rust but not much. How do I know which one is shitty?

>which one of thousands
That's the trick isn't it?

Still, it seems like your case is on one of the more important circuits, such as the negative cable to engine connection, so I'd start there and just clean the connection with a wire brush etc. If that doesn't fix it then you'll probably have to get into pinpoint diagnostics with a good digital meter and wiring diagrams and using the "voltage drop" method of looking at circuits while they're on. Should be plenty of youtube videos on how to do that.

tl;dr it might not be easy



Didn't we already fucking told you how to fucking fix it?

You can also try taking off one relay or fuse at a time and see if that eliminates the problem. I've used these method a couple times and helps me out to get closer to the circuit that's causing the problem.

Will try that

Anymore ideas?

That's pretty much it man, once you know what circuit is messed up you gotta inspect ot and see if any wires got damaged or loose grounds/terminals. Check grounds and voltage drops with a meter.

Other than that it would be to start changing components but thats expensive. Just be patient while troubleshooting or you can miss an obvious thing.

So basically try starting the car taking off one relay at a time and seeing where at goes?

Anymore ideas?

That's it buddy. You have to decide what is worth more to you, your time to find the issue or the money the shop is gonna charge you.

your vid makes me think you have an ECU going bad

Replace the thick cables that go from your battery to everything else. Both of them. Dremel the bolts they connect to and make them shiny in order to ensure the connection is solid. That's the easiest and cheapest thing you haven't tried yet.

These cables could be corroded inside of the plastic sheathing, it happened to me and produced the worst and most confusing series of electrical gremlins I've ever encountered.

>tfw was showing off my new car to my friend
>he turned on a cabin light for something after we parked
>leave door open and wander around talking about it open bonnet etc
>close door and forget about the light
Charged it up again overnight

Less than a month later
>buy some baguette and sandwich shit late at night from a store, put in passenger seat
>drag shopping bag through driver side, scrape roof with baguette a little
>battery dead the next day
>find out the baguette hit the cabin light switch
>charge it again
I just know this battery is gunna pack up early. I've mistreated it pretty badly.

>not driving leds