Ground Wire, O2 sensor, or Fuel Filter

[sirpowwow]

I have a 2005 GT and over the last 2 days the check engine light began flashing.

I ran a scan and got so many codes, I'm not sure where to start. Today while driving the check engine light came on and kept flashing. I can start the car but it shuts off within 60 seconds. I was planning to swap out my O2 sensors but I'm beginning to think, due to the voltage errors, its a ground wire issue. I've never seen both O2 sensors failure errors and I've had a few mustangs.

If its an electrical issue, my first guess is alternator replacement however I'm not solid with electrical work. Curious what you lot think is the best place to start?

 

[TexasBlownV8]

All of those are not going to go "bad" at the same time! A ground or voltage supply issue is more likely. If there was recent work such as removing the transmission or headers installed, there is probably engine harness damage and a subsequent fuse is blown.
I would measure voltage at various points and diagnose accordingly. Whatever you do, DO NOT START BUYING AND THROWING PARTS AT ALL OF THESE..unless you want to waste time and money. Figure out what is going on first, or find someone who can diagnose electrical systems with you.

 

[Forty61]

I see multiple codes in there showing high voltage, I would personally start by verifying battery voltage with the engine both off and on, confirm all connections at the battery, alternator and all grounds. Go from there.. my gut would say failing alternator.

 

[TexasBlownV8]

I see multiple codes in there showing high voltage, I would personally start by verifying battery voltage with the engine both off and on, confirm all connections at the battery, alternator and all grounds. Go from there.. my gut would say failing alternator.

Good point there.
Check the voltage with engine running (and off), and see. If engine off voltage is over 13 volts, it could be a battery problem. If voltage is over 14.5 volts when running, especially if over 15, the alternator is overcharging/over-voltage and that can cause all kinds of issues. It's more common on the 4.0L where there are at least two different alternator / PCM setups for different year models, and the wrong one can create over-voltage and similar issues.

 

[sirpowwow]

Man, I got back to the forum a bit too late. I swapped out the cam position sensor along with the spark plug for cylinder 6. What's strange is now the engine won't turn over! The spark plug looked very burnt on the bottom half, almost as if oil reached it and burned. I'm not great at the electrical side of things, perhaps it's time to learn. So I'm not taking measurements from the wiring harness, just the battery terminals.

 

[Forty61]

I would not throw any more parts at it without actually diagnosing something.

To properly check your electrical system you're going to need a decent voltmeter, set to DC voltage. Measure at the battery terminals with everything off and write down your number, I would say then start the car and check it again but you said it won't start now so that needs to be figured out first..

Stick shift or auto? Ignition comes on but motor won't crank or you have no power inside at all?

If diagnosis is not your strong suit post a reply here with details on the car (trans, miles, mods) and what your resting (ignition off) voltage is at the battery as a start. I would also be curious if anything was worked on or changed before that light came on, that would help determine a problem that was introduced or a failure somewhere.

 

[Kev555]

With that many codes at once its most likely a voltage/electrical issue. i second what forty61 said don't throw any more parts at it until you diagnose the issue. Battery, alternator and earths checked first.