Hello, first time posting so forgive any errors please.This all started with the common saying, bad things happen in threes... BATTERY, ALTERNATOR, RADIATOR.

A family member handed over their XJ to me after they found out I had my last car in a wreck. Everything on their XJ was fine, I upgraded my car deck to an aftermarket one and that was going fine. Just changed the bottom radiator hose and changed the radiator fluid. Next I changed the oil myself and that went fine as well. Minor leakage but what can you expect with a vehicle with 150k on it. Everything seemed to be going grand, as this was a free vehicle that looked very well maintained.

Hopefully someone has a solution for me. Per a friend's advising, I used the multimeter for checking continuity by placing my negative terminal on its post and leaving the positive terminal detached. Then I checked if it had any resistance but it showed an infinite reading and no value so there shouldn't be a short reading from the battery. I also took a reading at different times to see if the cell was getting a drain when the car was off after 20+ minutes then turning the ACCESSORY on. After 20+ minutes the battery multimeter value still showed a 12.57v so there wasn't really a drain going on. I'm leaning towards a charge issue but at this point I'm not sure what is the culprit. New battery, new alternator, new serpentine belt. I could start replacing a bunch of things like starting at the terminal wires and see where that goes but this is proving quite spendy already chasing this. So any suggestions would be great. Otherwise it'll have to be straight to a shop for me to spend hundreds for them to diagnose this problem. Thanks in advance.

Edward

 

Sounds like a charge issue. The battery voltage is good, so the next thing is to test the charging voltage. Just start the car and let it idle, and meaure the voltage at the battery terminals. You should see about 13.8 volts. If it's still showing the 12.57 or so, you are not charging.

The P1682 code is just telling you the charging voltage is too low.

If it's not charging, take the alternator to some place like Autozone. They will test it for free. If it fails, well, their Duralast brand is pretty decent. Just pick up the new one and pop it in.

 

Hey thanks for the response! Yeah I did say earlier that I took multiple readings after keeping it running and the readings from multimeter were 13.56v when charge works then drops to 12.9v at shutoff. That will dwindle to resting voltage of 12.51v eventually. Just when p1682 code comes out with CHECK GAUGES light the voltage goes from 12.51v to 12.41 w/ door lights on, to 12.29 w/ ACCESSORY on, to 11.53v when CHECK GAUGES light comes on, finally to 11.34v when engine electric fan turns on.

This is the 2nd alternator, 2nd battery, and 2nd radiator since I got it a few months ago. O'Reilly's said new battery and new alternator test good.

 

Before throwing money and parts into the Jeep, I would suggest you go through and clean and renew all grounds, connections, and the ECM connectors. You may also want to check your battery cables for hidden corrosion under the insulation. Visually inspect both the underhood fuse and relay box for corroded fuses and relays as well as the fuse box under the dash. Keep your eyes open for anything that may not look right and investigate. If all this doesn't correct your problem then you may have sensor or sensors that are faulty or an ECM problem.

Hope this helps

 

Yep. What he said. It's amazing the crazy things that poor connections can do, especially poor ground connections.

 

I recently chased down a parasitic-type drain that was quickly draining my battery dead. It was my rear wiper blade motor. Something was wrong with it.. Even when my ZJ was fully turned off, the rear wiper blade motor was still pulling a steady approx 200 miliamps. The rear wiper blade motor was even turned off..

I disconnected the rear wiper blade motor completely. Something I noticed after fixing the parasitic drain I had here at the rear wiper blade motor was with involving my alternator. Previously, my Jeeps alternator was only putting out 13.8V at best. With the fault removed at the rear wiper motor. I immediately noticed that my alternator began putting out a full14.25V to the battery with this rear wiper blade motor now being disconnected. The fault here in this circuit was not allowing my alternator to deliver its full charging voltage...

It sounds like you have one of two problems occuring. Or, maybe it is both.. There is either voltage drop happening somewhere. It could also be related to having too much resistance on your earthing, or in the ground.

I think since you have such a large lack of proper voltage getting to your battery.. The starter would be something I would want to fully and thoroughly scrutinize to check it out. It is tied in closely to the battery and your Jeeps alternator by large gauge wires. If you are losing electrons here at the starter wirings, it could cause a drop in voltage being routed wrongly away from where it needs to go.. instead of the correct charging voltage being able to arrive fully and properly like it should to the battery.

I would want to use a voltmeter in order to closely examine exactly what is happening between the positive connection for output on/at the alternator leading to the battery. I would be looking for a voltage drop that may be occuring within this wire.

I would want to check the main engine compartment ground(s) too. I would be looking for an abnormally high resistance happening with and along the ground(s) wires themselves, and at their connections.

You might also want to take a voltmeter to all of the different fuses. Setting the meter to milivolts.. Touch each of the meter probes from the voltmeter to the location on the fuses utilized for testing.. to look for a draw of abnormal voltage that is possibly occuring on any one of the electrical circuits of your Jeep. It is possible you may find several circuits drawing your volts away (from getting to the battery from the alternator). Find out what all is located on each of the fuses. Turn those things on one by one (ie: headlights, turn signals, rear wiper blade motor, front windshield wiper blades motor, radio, etc..).. Find out what they are supposed to be, or not supposed to be drawing in millivolts (look up 'voltage drop fuse chart conversions table'.. to be able to convert their measurments of millivolts to their miliamps conterparts is how to know). Test them while the Jeep is fully turned off.. and then test all of the same fuses again, but this time with the Jeep on and running. Then, test them with their associated accessories turned to their on statuses.

I hope you can find the reason...

 

Hey thanks BruceB for the response!

So I'm really trying to focus on diagnostic checking the vehicle to get more of an idea of where the problem is before I go around checking every ground and all continuity in all the many harness to check at. I do know the p1682 code has already been tied to multiple areas but I'm getting more of a vibe that it is the voltage regulator is the culprit after speaking to a few folks about the situation for the p1682. I do want to reemphasize that the vehicle does charge the battery under certain conditions (i.e. the vehicle needs to be warmed up for a bit, then the ignition needs to be turned off and on several times until the voltage gauge indicates it is getting ~13v at which point I know the alternator is giving charge to the battery). I've even been told to check the voltage drop after warming up the vehicle and then turning it off for 15-20 minutes and then check multimeter readings with just the ACCESSORY on to see if I can see a voltage drop that gives off a significant enough tell. Or told by another mechanic to pull the AC adapter as it happens to do the trick with domestics from this time frame. But I'm suspecting it has more to do with charge than it has to do with a drain.

So, before I go into countless hours of continuity checking wires, cleaning off all grounds, or even replacing a new ECM or installing a voltage regulator kit I want to make sure it has more to do with one vs the other. The continuity check makes sense to keep doing if I wasn't sure if my battery was the issue for proper charging. But after replacing battery, replacing the alternator, we have to ask what could it be stopping the alternator from charging the battery in conjunction with the p1682 code. which makes me feel it's the voltage regulator that is the problem. Knowing that the car will charge the battery only after warming it up make it feel like we don't have a continuity issue as much as charge problem. Can you suggest a test to see if the voltage regulator doesn't have a role in the battery not charging?

 

As I understand it the voltage is regulated entirely by the PCM, which you seem to be aware of.

I have seen threads about bypassing this with an external regulator, and they may give clues on how to test for the fault

 

I myself bypassed the internal regulator with one from a dodge truck, and it works great. You ask if there's a test, well, not really but you could 'full field' the alternator just for a second or two and see if it charges at like 15 volts, I don't recommend that. The thing to consider is, is the battery capable of holding a charge or is it loosing charge; and I agree that if you replaced it a couple times it's more likely the regulator.
One thing that's confusing, you say 'voltage drop' when you mean that the battery voltage drops. That is not what voltage drop means. A voltage drop is measured Across something, some part of a circuit, to tell how much of the available circuit voltage is 'dropping' across that part of the circuit. Then according to Gustav Kirchoff's voltage law, the voltage drops in the circuit must add up to the driving voltage, or put another way, the driving voltage will drop around the circuit until the algebraic sum is zero.

Anyway...A fully charged battery will hold at 12.6 overnight, then take it down to AZ land and have them test it out of the car, if ok, I vote for the regulator.

Not sure if the 99 has the Battery Temp Sensor, if so that would also affect charging somewhat, probly not to the extent you are having.

 

I might add that the internal regulator by Chrysler was a blatant attempt to save money and go cheap with an IC integratged into the PCM instead of the stand alone regulator, and a horrible design flaw that is bound to fail. heh my 2 cent

 

Voltage drop is very easy to check for too. It would take barely a minute to do.

Turn all possible accessories on, with the Jeep running. Put the red dvom lead on the neg battery post. Put the black lead of the dvom touching to the alternators metal casing. Manually move the throttle body plate to open the throttle up to approximately 2000 rpms. Look for a voltage drop. That's it. Your done...

Any reading greater than 0.1 - 0.2V dc = 'probably most likely' a significant enough voltage drop is occuring for on the ground side... (would have to actually read a specs sheet to know this value. I believe it is zero though?).

Then, you can check for voltage drop next at the positive side of things. Which is also a very simple thing to do at the positive battery cable side.

Does anyone think the 'fusible link' may cause these symptoms? I do... I would be checking it.

You definitely want to go at it with a plan. But, sometimes you just have to start testing to begin ruling things out.

When it is getting crummy charging voltage, I would do the full field test.... That'll help determine a fault at the PCM for the regulator possibility. If it gives you a full on charging output from your alternator when you do this test.. Then, you know that was the problem. If it doesnt? Well, then it is not a helpful enough test.. to keep that in mind. It could point it out though if it were at the PCM. Otherwise, it could be multiple other things...


You could run the Jeep for awhile and then grab hold of your positive battery cables. If they are really hot! That indicates too much resistance is occuring...

 

We assume you meant "Look for a voltage drop" and not a 'resistance reading'; and that you meant 0.1 - 0.2 VOLTS DC. Actually, such a reading might be normal, I would check the FSM to see what the allowable drop is between the two points you mention with 'all possible accessories on'.

Full fielding the alternator might harm something like the pcm. Also it is tricky because one of the little tiny way up underneath field connections is the ground, if you put 12v to that instead of the other one, you'll have a spark show while laying under a running vehicle.
Much easier to drive to AZ and get a computer printout of the diode function too.

 

Now that I think of it one side of the field is always hot, the other is the pulse width modulated ground signal from the PCM, so if you wanted to full field it you would identify the pcm ground signal, disconnect it from the pcm, and connect a full ground to the alternator . But don't do it.

 

My experience with voltage drop started like this. I was driving along and the Jeep "bucked" at around 45 mph.. Immediately the check engine light cam on and the voltage meter indicated very low volts. I forget the exact code, but it referenced to a signal interruption in the cam sensor. I cleared the code in a parking lot and the Jeep started right up, voltage was normal and I drove home. Two days later the Jeep would not start, though it would turn over and got the same code. Again, cleared the code and the Jeep started right up. I replaced the cam sensor thinking that was the problem, About a week later the Jeep wouldn't start, had no codes or check engine light, and the OBDII port was dead. Went through a very thorough diagnostic of the electrical system and sensors (this is the link to that story, https://www.cherokeeforum.com/f2/sen...roblem-251669/) . Ended up that the PCM had failed. I ordered a replacement PCM and, knock on wood, haven't had a repeat of indicated problems.
My advise is that you really have to start out with the basics of diagnostic tests to isolate the PCM/sensors/electrical problems or you can go the more expensive way and replace parts until everything is back to normal. That is what stealerships do anymore for diagnosing a problem. There is more than a wealth of information just on this site as well as on the internet. Key is to be patient, keep a sense of humor and be thorough. Like BlueRidgeMark states, don't just think the connection is clean, take it apart and make sure.
hope this helps

 

Yes sir. I amended my post above to reflect correctness to the matter.

If it is a fault due to the regulator function of the PCM? It would be a relatively simple fix to bypass it here at the PCM completely.. Bypass it to add in an external regulator instead. This would fix the problem (if it is the reason..), and it could be considered the same as adding an upgrade. As the PCM controlling the regulator function is far less superior to the externally controlled regulator units from what I understand.