TJ won't start: What's wrong with my Jeep?

ObedaTJ

ObedaTJ

TJ Enthusiast
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Joined
Nov 1, 2018
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Location
New York
Okay so the other day I’m out, driving around everything is fine. Stop to get ice cream and turn the Jeep off. It won’t turn on. Sounds like it’s a dead battery, okay cool. At first I thought it was no gas but I know if it had no gas it would at least crank. So I got a spare gallon I had in my trunk and put it in there. It turned on, weird. I’m like okay this day might be okay, head home. On the way home the lights on the dash start to dim. My radio is off the entire time. My horn barely works. Thinking it needed more gas I rushed to a gas station turned it off and put more gas in it. Nothing, had someone jump start me, it turned on but I knew it would die soon, rushed my ass home and it turned off in the driveway. I didn’t mess with it after that.. Next morning my dad checks it out and says it’s the alternator okay so I go get a used one from a junk yard just to get me going for the next few weeks. Me and my dad replace it, still nothing. Then my dad is like it’s the battery, at this point I wanna tell my dad “are you serious” go to autozone and get a new battery. Pop it in, it starts. The gauge however would stay at 12 and then drop to 9 a few minutes later. I drove it 150 miles that day and then when I was getting home it started dying. I noticed when I put the new battery in it would have a slow crank.

My Jeep is a 2000 Wrangler 4.0

What should I do now, I don’t want to take it to a shop and replace the alternator when I could do it myself. My question is how would I know if it’s the alternator because I can believe that both alternators suck but the battery is brand new.
 
ObedaTJ said:
Okay so the other day I’m out, driving around everything is fine. Stop to get ice cream and turn the Jeep off. It won’t turn on. Sounds like it’s a dead battery, okay cool. At first I thought it was no gas but I know if it had no gas it would at least crank. So I got a spare gallon I had in my trunk and put it in there. It turned on, weird. I’m like okay this day might be okay, head home. On the way home the lights on the dash start to dim. My radio is off the entire time. My horn barely works. Thinking it needed more gas I rushed to a gas station turned it off and put more gas in it. Nothing, had someone jump start me, it turned on but I knew it would die soon, rushed my ass home and it turned off in the driveway. I didn’t mess with it after that.. Next morning my dad checks it out and says it’s the alternator okay so I go get a used one from a junk yard just to get me going for the next few weeks. Me and my dad replace it, still nothing. Then my dad is like it’s the battery, at this point I wanna tell my dad “are you serious” go to autozone and get a new battery. Pop it in, it starts. The gauge however would stay at 12 and then drop to 9 a few minutes later. I drove it 150 miles that day and then when I was getting home it started dying. I noticed when I put the new battery in it would have a slow crank.

My Jeep is a 2000 Wrangler 4.0

What should I do now, I don’t want to take it to a shop and replace the alternator when I could do it myself. My question is how would I know if it’s the alternator because I can believe that both alternators suck but the battery is brand new.
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What was the voltage gauge showing while all this was happening?
 
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Do you have a multi-meter? If not head over to Harbor Freight or autozone and grab one. You don't need a $300 fluke meter, you can get a cheapo for $15 for basic troubleshooting.

I would get the thing running and see what the output is at the alternator. Put the black lead of your meter on the negative battery terminal and the red lead from your meter on the terminal on the back of the alternator. This will give you the output voltage of the alternator and it should be somewhere in the high 13's, and if everything is working normally this should also be what you measure across both battery terminals while the engine is running.

If you get 13+ volts at the alternator and less at the battery, you have an issue between the alternator and battery.
 
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Okay so I don’t have a multimeter but I replaced the alternator and battery to be on the safe side. They weren’t the issue. Charged it up and still goes back down. It won’t hold its charge.

Now I’m getting a code. P1495
What does this mean?
 
Ok, so if you've replaced the battery and the alternator I would suggest grabbing a cheap meter and measuring some voltage.

So at this point the voltage gauge on the dash is reading low? Do you have the red battery light illuminated on the instrument cluster?
 
qslim said:
Ok, so if you've replaced the battery and the alternator I would suggest grabbing a cheap meter and measuring some voltage.

So at this point the voltage gauge on the dash is reading low? Do you have the red battery light illuminated on the instrument cluster?
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I never had the red battery light illuminate
 
Sounds like a bad connection either at the battery terminals or the other end of the ground to chassis, not allowing the charging system to do it's job. Other possibility is a dead short.
 
Edit: you need a multi-meter.

Leak Detection Pump P1495 LDP, not related to charging system, not to say that the low battery state didn't cause the computer to trip this code (unlikely).
Check voltage at alternator with engine running, should be at least 12.5 vdc (usually between 13 - 14 vdc) check again at battery terminal, make sure you put the lead on the terminal not the clamp for the cable. This will tell you if you have a voltage loss between the alternator and the battery.
 
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Someone on another thread I was looking at said, "before trying to diagnose any electrical issues, disconnect the battery, and take all the ground leads off and clean up the connections." That'll rule out any bad ground connection issues.

The code — Error Code P1495 is defined as VAP Leak Detection Pump Solenoid Circuit Condition. This code pertains to a fault in the Leak Detection Pump.

Error Code P1495 refers to a problem in the vehicle’s leak detection pump, which is part of the emission system. This code is detected when the PCM (powertrain control module, also known as ECM or engine control module in other vehicle makes) determines that the solenoid did not change status when activated. Most often than not, this code appears when there is a bad leak detection pump.

I'm not sure if there's a way to test the circuit (because if it's good and you replace it, then you're just throwing parts and money into it for nothing), but I would at least take a look at it. Check all the connections with a multimeter. The FSM's or a Chilton have good information on finding and sometimes testing components.
Factory Service Manuals (on the TJ Resources sticky)
Youtube also has tons of good videos on how to test sensors and things like that. Theres this guy ScannerDanner on there that teaches at some community college and he has a lot of helpful stuff when it comes to electrics. (he is kind of long winded though, most videos are about 45-50 minutes)


My very limited experience would say a decent multimeter is about the best 20-30 bucks you can spend right now.

Oh, and if there's one thing I've learned so far, if you replace a sensor or any kind of component that talks to the PCM, ONLY use OEM parts. I'm sitting here with stalling/rough idling Jeep waiting on a TPS from the dealership cause I used an aftermarket one that failed after a couple weeks. As my grandpa says, "I can't afford to buy cheap"
 
What everybody else has said. Get a multimeter! You can't fix a problem if you don't know what the problem is. That used alternator could be n.f.g., or it could be great. Don't know without a multimeter. Could be a ground. Don't know without a multimeter. Trust me, it will be used again and again.
 
Goatman said:
What everybody else has said. Get a multimeter! You can't fix a problem if you don't know what the problem is. That used alternator could be n.f.g., or it could be great. Don't know without a multimeter. Could be a ground. Don't know without a multimeter. Trust me, it will be used again and again.
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Battery is good testing at 11.6 I checked the alternator and it’s also checking at 13. The alternator not the battery are the problem. Just changed the belt as well and same thing
 
Disconnect the negative and then the positive cable from the battery. Switch the mutli-meter to Ohms and check for a direct short on the positive cable to the chassis.
 
Just had it looked at by a few shops. They all said the same thing, bad computer. They checked grounds fuses everything is fine.

Where would I get one and could I install it myself?
 
Junkyard or Rock Auto has Mopar PCM's $$$ ouch. I personally have had bad experience with "A1 Cardone" and will not use their rebuilt computers, but that's just me, you will have to make your own judgement.
 
I was just in the Service Manual and looked at your code:
Capture.PNG


If your Leak Detection Pump circuit is actually shorted? Might be the source of the entire problem?
 
ObedaTJ said:
Battery is good testing at 11.6 I checked the alternator and it’s also checking at 13. The alternator not the battery are the problem. Just changed the belt as well and same thing
Click to expand...

Ok, so you read 13 something volts at the alternator while it was running and only 11.6 at the battery? This sounds like the alternator is working but it isn't making it to the battery.

Another simple check at this point is to ensure that the fusible link between the alternator and the battery hasn't blown or that you don't have another problem in that circuit. Disconnect the positive terminal on the battery and the terminal on the alternator and check for continuity between the two.

You'll be measuring for ohms here and should be getting a reading in the low single digits. If you get an open reading (or OL) then you have an open circuit between the alternator and the battery. See below, this is from your FSM. The highlighted path is the circuit between your alternator and battery. If you have good charging voltage at the alternator but don't have it at the battery then there is an issue somewhere in that circuit.

Capture.PNG
 
ObedaTJ said:
Battery is good testing at 11.6 I checked the alternator and it’s also checking at 13. The alternator not the battery are the problem. Just changed the belt as well and same thing
Click to expand...
Those numbers are low. The battery (while the Jeep is off) should be reading around 12.6 volts, and with the engine running, around 1-2 volts higher than that.
 
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11.6 on the battery means either the battery has a bad cell or the whole battery is mostly discharged. At that voltage getting it to crank and start is a surprise. Put a charger on that overnight to try and get it up to snuff. If it won't charge up to 12.6 by morning then you have a battery problem. A good alternator should be higher too, but that reading could be due to a battery fault or some other large voltage drain on the system.
 
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Okay not getting that code anymore. I swapped the battery out at an Autozone and there was nothing wrong with it but they replaced it anyways. I am still having the same issue. Checked grounds, checked all fuses, changed terminals. Alternator was replaced three times. Most of the guys that saw said it is the PCM. I ordered one on Flagship and they said it would ship within 1-2 business days. It’s been over a week and no update from them. I tried calling, emailing, nothing. I don’t want to go to my bank and chargeback just yet. How can I get in contact with them.
 
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