03 P5 won't start

[jonesymj]

First off, I did search lol. Nothing bugs me more than people who don't. So I hope I didn't miss the simple answer somewhere, I swear I looked first!

So my 03 automatic P5 died while I was driving today. No bangs/booms or any catastrophic noises. Just died. Will not restart. Cranks all day long, but will not catch, doesn't even try.
Symptoms:
INJ/FIP fuse (30a pink one) in under hood fusebox is blown. Replaced it, and it blew again as soon as I turned the key back on to the IGN position.
Temp needle pins itself when I turn the key on to IGN position. I had only been driving for 5 minutes when it died this am, temperature hadn't even come up to normal, let alone overheating. The needle was acting normal until then. Car has been sitting for 5 hours now, I assure you it's not overheating. Temp needle still goes straight to maxed out when I turn the key on to IGN.
Code reader/scanner won't work. It says it can't connect to the system/vehicle. Tested it on a Dodge and a Lexus (just what I have handy) and it works fine on both of them, so it's not the code reader. And now I have to do the O2 sensors in my sister's Lexus, too lol.

So hit me with your ideas everyone. Obviously, the reason it won't start is a fuel problem. But why does the injector fuse keep cooking? Could this be the fuel pump relay? I'm open to suggestions, so let them rip!

 

[Ilikebikes]

Dead ECU?

 

[pcb]

INJ/FIP fuse (30a pink one) in under hood fusebox is blown. Replaced it, and it blew again as soon as I turned the key back on to the IGN position.
Temp needle pins itself...

You've got a dead short somewhere...

That fuse is for the "engine control unit" and probably supplies power to your OBDII port as well... No power in the port and your reader won't connect.... And it could easily make your gauges go wonky.

You probably had a wire wear through its casing and ground out or fall off and ground out.

You need to find where your short is.

 

[pcb]

You may have had a component like the fuel pump fail but they don't normally short out when they do.

 

[jonesymj]

@pcb I'm 6'6" dude... No way I'm short hahaha

Well I figured it was something along those lines, I was an auto-electric guy for a lot of years, I just hate chasing things like that down. I'll check over at the ECU, maybe I'll get lucky and it'll be an obvious one.

I appreciate the help so far, and keep em coming, folks... I'm car-less until I get it sorted, so I have lots of reading time available...

 

[MrGiggles]

Look over the wires to the fuel injectors, coils, and the crank sensor. Those all get the full 12 volts from the PCM, and would cause the fuse to blow if shorted.

 

[pcb]

I'm betting it's not the ECU... It's well protected and stays clean and dry.
I don't recall anyone here on the forum who has had an ECU fail.

It's probably a wire under the hood where it gets hot and cold and wet and has been bouncing around and vibrating for 15 years.

Try unplugging various components connected to that circuit and testing them for continuity.

(I'm still betting its a wire that wore through and grounded out)

Good luck chasing down your Gremlin... They're tricky little bastards...

 

[pcb]

So... For curiosity sake I went out my car and pulled my "INJ" fuse then turned my key to IGN and the Temp gauge went to max...

So that part is normal with that fuse being blown.

 

[jonesymj]

I'll go poking around the motor a bit in the morning, then... I didn't see anything obvious when I looked earlier, but I won't lie it was a cursory check over for just obvious things. Guess it's time to put on my "Capt. Thorough the Electro-gremlin fighter" outfit, and really go to it. Just like being back at my old job again... Sigh!!

And thanks for that test, pcb! That's one less thing I need to chase down.
2 Beer on me if I'm ever in your neighborhood lol!

 

[Hank3]

I had a stalling and no start issue last year. Troubleshooted for a couple months. Turned out to be a bad fuel pump relay. May want to check into that (short video clip and my troubleshooting saga in link below):

http://www.mazdas247.com/forum/showthread.php?123847050-P5-Won-t-Start-amp-Rough-Idle

We tested the fuel pump relay by itself and it worked fine (it was clicking), but once it's heated up, that's when it would cause the my P5 to stall; and subsequently no start as well until the car cooled.

 

[pcb]

I had a stalling and no start issue last year. Troubleshooted for a couple months. Turned out to be a bad fuel pump relay. May want to check into that ....

He's blowing his fuse though...

Unless some relay or other component has shorted out internally, then he shouldn't blow a fuse.

 

[jonesymj]

Update: Still no love.

Took the under hood fuse box out today, to start checking for broken or rubbed thru wires. Found that the White/Blue wire NEXT TO the White/Green (which, from the pic that pcb posted above is supposed to go to the ECU) is scorched/darkened. This wire is connected to (tested by continuity) the ECU relay in the under hood fusebox.

So here's the kicker... I found the White/Blue wire at the ECU, and the short goes away as soon as I unplug the ECU. Meter the Blue/White to ground with ECU plugged in? Continuity. Unplug the ECU, meter the same wire? No continuity. This is with the injectors, coils and pretty much everything else I can find under the hood, unplugged or disconnected.

I'm not trying to blow off the answers/suggestions that you folks have already given me, but is it just me or is the ECU starting to look like the prime culprit here?

 

[pcb]

.

I'm not trying to blow off the answers/suggestions that you folks have already given me, but is it just me or is the ECU starting to look like the prime culprit here?

OK... So how bout you disconnect the ECU plug in a new pink fuse and turn on the car.. .

If you still blow your fuse you know it's not the ECU.

 

[pcb]

Here's what the FSM says about a car that won't start...



Replacing the ECU is always the last thing they say to do.

 

[MrGiggles]

Update: Still no love.

Took the under hood fuse box out today, to start checking for broken or rubbed thru wires. Found that the White/Blue wire NEXT TO the White/Green (which, from the pic that pcb posted above is supposed to go to the ECU) is scorched/darkened. This wire is connected to (tested by continuity) the ECU relay in the under hood fusebox.

So here's the kicker... I found the White/Blue wire at the ECU, and the short goes away as soon as I unplug the ECU. Meter the Blue/White to ground with ECU plugged in? Continuity. Unplug the ECU, meter the same wire? No continuity. This is with the injectors, coils and pretty much everything else I can find under the hood, unplugged or disconnected.

I'm not trying to blow off the answers/suggestions that you folks have already given me, but is it just me or is the ECU starting to look like the prime culprit here?

Get a wiring diagram and see which wires are +12v outlets from the PCM. The fuel injectors, coils, and crank sensor would be examples of that. Probably the fuel pump and 02 sensor heater too.

Once you find that out, check each one of them for continuity to ground with the PCM plugged in. See if you can isolate it to one wire and then trace it.

 

[pcb]

This might help...

 

[jonesymj]

Mr. G: That's kinda what I was thinking, but wasn't sure what wires were supposed to meter what... But...
Along comes pcb with another wiring schematic! Thanks guys, you're making an unpleasant job about as easy as possible!