Lots of sensor errors

MLB

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Jun 25, 2016
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Hi folks,

I had an 06 Mustang V6 for a bunch of years, and in May, found myself the 09 GT I'd been longing for. 31k miles, everything works perfectly. Terrific car. Today is the first issue though:

I got about a couple hundred yards down the road and the low oil pressure warning goes off. Just about to shut it down, and the low brake fluid warning chimes in next. Then the TPS sensor error, and then Parking Brake On warning. After a few more seconds, all of the warnings and lights go away. Aftermarket radio working from an audio standpoint, but screen is stuck on backup camera with a blank screen. Car is running fine the entire time. Pretty sure everytihng didn't fall apart at once, but stopped to check the oil anyway. All good there. Start it back up, and just about every 60 seconds on the dot, all the error warnings repeat. I noticed that the turn signal has a weird pattern as opposed to the regular rhythm too.

So, I've had the car about 4 months, I added the Pioneer radio, Maestro system, backup camera, and a trunk release button about a month ago. All have been working fine since then. I'm thinking I may have mucked something up, but odd that it didn't occur right away.

Trying to figure out what is the common element between all of these sensors, first thing that comes to mind is a ground of some sort, or a problem with the BCM computer (ugh.) Two heads are better than one, and a few hundred heads have to be even better ;-) Anything jump out to you? I plan on backing out my camera and radio to see if that solves anything, but that's a messy job if it's not the issue.

Thanks for your advice!
Mark
 
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Bullitt95

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Jun 13, 2007
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Check the passenger side front footwell and SJB for any water intrusion. It's possible the cowl drains are blocked causing water to accumulate, which then finds its way into the cabin via the air filter.
 

MLB

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Jun 25, 2016
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Thanks. I had that problem with the '06, but this one is bone dry (thankfully). I'm leaning towards a ground or power quality problem. I'll isolate my radio work first though.
 

MLB

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Jun 25, 2016
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So, I disconnected the backup camera, and what looks to be an aftermarket progressive tail light board. No help there. Still the erratic blinker pattern. I'd imagine that if I took it for a ride, errors would be blinking away.

Before tearing my console apart again, I thought I'd disconnect the battery (reset the computer), clean up the terminals, and take another look. After a buzz and a chirp from the horn, the computer seems to have rid itself of it's malady and everything is behaving well again. A rather exhuberent ride around the block was a sucessful test.

Now to see if it comes back after a while...
 

MLB

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Jun 25, 2016
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Well, that lasted for a couple of weeks. Back to the blinking barrage of error lights. Will try a battery load test in the delusion that it will be a simple fix, and then will continue on to digging out my Mastro computer and radio to rule those out.
 

Bullitt95

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Jun 13, 2007
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Another thing to check for is a faulty alternator diode that could be leaking AC current into the main wiring harness. A simple AC ripple test (as described in YouTube) with a digital voltmeter will either confirm or rule out this diagnosis.
 

MustangIIMatt

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After doing the ripple test @Bullitt95 suggested, take your battery to be tested at one of the parts stores, they'll do it for free (and can even do it in-car). S197 cars are particularly prone to phantom faults when the battery is weak, even one that's still strong enough to start the car.
 

racerraj

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What Bullitt95 said about the alternator is worth checking. And most parts stores will test the alternator in the car too.
 

MLB

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Jun 25, 2016
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I'll learn about the ripple test. I thought I had a problem there when I read about 9vac blip every second or so, but my truck does the same thing, running or parked.

So I went to load test the battery after not driving it for a few days, and the battery was down to 8v. So, something could be draining it, but since it's likely over 5 years old, I ended up replacing it. All seems well again. We'll see how it holds up.
 
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MLB

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Jun 25, 2016
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Nope. My quest for (overly) simple solutions is coming to an end I think. I have a cheapo O-Scope kit that I put together a while ago. Tiny screen. Hard to see the waveform for the ripple test. Time to find a friend with some real electrical tools.

I was considering disconnecting the alternator to see if that eliminates the problem. Should be able to run off the battery for a short while, but sometimes it works for a day even as is. It will be hard to rule out the alternator without disconnecting it for a couple of days.