P2503-00

[Conrad 16.5]

You bought a used alternator? Did you test the old alternator?

A simple test, if you have a voltmeter, is to check the voltage at the battery before starting the car. It should read in the vicinity of ~12.5v.

I just now checked the battery in my 2016.5 CX and it's a bit low at 12.2v. This is the original battery so it may be time to change mine out in the near future.

Now start the car and check the voltage at the battery. After a couple of minutes, it should jump to around ~14v. If it doesn't jump up, then your alternator is suspect.

An update on my low battery voltage.

When I checked the voltage of my battery at 12.2v, this was immediately after unlocking the car in order to pop the hood (CX hadn't been started for about a week). After about 30 mins I checked again and got a reading of 12.6v. I'm less concerned about my battery now but will be keeping an eye on it.

 

[edmaz]

An update on my low battery voltage.

When I checked the voltage of my battery at 12.2v, this was immediately after unlocking the car in order to pop the hood (CX hadn't been started for about a week). After about 30 mins I checked again and got a reading of 12.6v. I'm less concerned about my battery now but will be keeping an eye on it.

Yes, a week of inactivity is fairly significant, and the small, continuous, normal draw will pull any battery down to some extent over that period of time. The ongoing monitoring will tell you what you need to know about the health of that battery, and it may actually have a good bit of life remaining.

 

[yrwei52]

So, without any testing at all you decided to swap out the alternator?

Ok then...

Well, without a (cheap) multi-meter and after several tests by AutoZone and Interstate to his battery which turned out to be good, I think replacing the alternator is a right decision at this point. A used alternator from the salvage yard is cheap (still). And the error code P2503-00, the dash “battery” warning light (meaning: charging system problem), in addition to his CX-5 would die even if the car is idling, all indicate his charging system is having problems, not the battery itself.

Hopefully the OP will give us an update, and we’ll see if the used alternator would actually fix his problem.

 

[yrwei52]

⋯
What you did by leaving the car in accessory mode likely discharged it much more.

From my experience leaving my 2016 CX-5 in accessary mode for long, or even overnight won’t kill the battery. The system will turn off whatever the accessories automatically which are on in 25 ~ 30 minutes.

I did have an experience on other vehicles that leaving a dome light on for several days at the airport parking which killed the battery, couldn’t start the engine once we got back.

 

[Xitztyler]

Update soon : putting belt back on and putting connectors back on. I had to take tensioner out, I got the alternator in and out through the top.

 

[yrwei52]

Update soon : putting belt back on and putting connectors back on. I had to take tensioner out, I got the alternator in and out through the top.

Thanks for the update.

What year is your CX-5, and how many miles on it?

You should also check the tensioner as it’s very prone to leak. I may go ahead changing the serpentine belt and water pump stretch belt at the same time if these belts have never been replaced.

 

[madar]

Personally, if the battery is more than a couple years old, I'd just go buy a battery at Walmart and see if it fixes your issues before swapping alternators. The warranty on the current battery is probably pro-rated so you really aren't getting a free battery anyway and at some point your time is more valuable.

1000% agree. If the battery is over 4 years old all bets are off IMO. That Walmart battery is a good battery if you can find one. First rule of electrical diagnostics- always make sure you start off with a good battery. Best tool for testing batteries (any load tester):

https://www.amazon.com/dp/ (commissions earned)

 

[Xitztyler]

So I got my battery warranty out and also got a new alternator, battery light still on, I reset it with the obd2 scanner and it comes right back, should I drive a couple miles to see if it resets? Even though the obd2 cleared it and it came back?

Thanks for the update.

What year is your CX-5, and how many miles on it?

You should also check the tensioner as it’s very prone to leak. I may go ahead changing the serpentine belt and water pump stretch belt at the same time if these belts have never been replaced.

2016.5 120k

I got a multimeter I'm going to test battery alternator and ground.

So while running

Second that. Once it's running, it should be able to continue running on just the alternator.

To the OP: This is a crude test, but If you can somehow get it started again, put a voltmeter on the battery terminals while it's running. It should read about 14.5 volts. If it's still below 12 volts, more than likely there's a problem with your charging system. May be nothing more than a blown fuse.
Good luck

so while vehicle running new battery reading 12.22 volts.
Reading 12.5 with vehicle off.
Quick question, what is the wire running across the alternator that goes under it to a plastic connector, it looks like a ground wire where a screw and metal are hooked up to the frame. When I tried taking that connector off I ended up breaking it, I put the metal wire back in to the plastic piece and snap the plastic connector back on the plastic tab where it goes, but I don't think it's secured enough.
How do I check for bad ground to see if this is the culprit?
Also what fuses would I check for?

 

[RedBaron]

How do I check for bad ground to see if this is the culprit?

Now you have a meter, set it to the Ohms (or Resistance) setting, put one lead on the battery terminal and the other on the engine block and see what reading you get. Should be 1 ohm or less.

 

[Xitztyler]

Now you have a meter, set it to the Ohms (or Resistance) setting, put one lead on the battery terminal and the other on the engine block and see what reading you get. Should be 1 ohm or less.

With vehicle off? Also when I do this it says 0.00, should it be reading something? Maybe my multimeter is not getting a good ground

No its reading high I think it's that one ground wire I'm talking about that ripped out im going to try to make a better connection with it

I'm using the bolt to the shock mount

The ground is fine I have no idea what else to check at this point

The thing is when the problem initially happended, the warning on my infocenter would pop up randomly at different times. Especially when I was putting a load on the engine. Voltage drops on battery when I put a load on right now to (checked with my multimeter). After the issue started I turned off car, went back 30 minutes later started it and everything was fine. Turned it back off and another 30 minutes later started it and problem came back. So it was working a little bit after the problem but now it's completely not working

When this mechanic I stopped by real quick was banging on my alternator with a prybar and hammer that's when the battery light stayed on permanently before it was coming on and off with infocenter warning

 

[Jmaz]

When this mechanic I stopped by real quick was banging on my alternator with a prybar and hammer that's when the battery light stayed on permanently before it was coming on and off with infocenter warning

WTH?

 

[Xitztyler]

Well I live in like city area so mechanic was on the way to where I was going lol

 

[Xitztyler]

I think I fried the ecm by leaving accessory mode on to long I might need a reflash

 

[Conrad 16.5]

I'm done here, good luck.

 

[Jmaz]

I think I fried the ecm by leaving accessory mode on to long I might need a reflash

I wouldn't entertain that idea because I think the chances are remote if even possible. Stay away from the ECM unless you really want to screw things up. Instead concentrate on good battery and good alternator without getting into any side detours. And stay away from any "mechanics" who beat on alternators. That was a tactic reserved for starters. As I said in a previous post, this shouldn't be difficult. Good luck.

 

[wlong01]

I wouldn't entertain that idea because I think the chances are remote if even possible. Stay away from the ECM unless you really want to screw things up. Instead concentrate on good battery and good alternator without getting into any side detours. And stay away from any "mechanics" who beat on alternators. That was a tactic reserved for starters. As I said in a previous post, this shouldn't be difficult. Good luck.

Truer words were never spoken. Spot on advice.

 

[Xitztyler]

Thanks quick question guys, since I bought a salvaged alternator, and I know i have a new battery. How can I truly test the alternator alone? Without finding open circuits within alternator and battery. I'm just trying to do a sole alternator test. I have a multimeter. I just want to see if the salvaged alternator is working? Or I can put my old one back in

 

[Odrapnew]

Take alternator out and bring to a parts store that tests them.
If you have the old alternator, you could bring that as well.

 

[Xitztyler]

Where is the voltage regulator in these cars? Are they built in with the alternator?

 

[Buzzman12]

Where is the voltage regulator in these cars? Are they built in with the alternator?

Wow. Are you sure you should be doing this yourself?

Cars haven't had external voltage regulators since the late 60's, early 70's.
Voltage regulators were built into the alternator when car manufacturers stopped using generators, back in the 60's.
Some new cars don't even have regulators built into the alternator anymore. A lot of modern cars are now regulated through the ECM.