battery light keeps coming on again

[flair1111]

ok so a few days ago i replaced my alternator because the bearings in it started seizing up making a horrible sound. i replaced the alt...belt and pulley tensioner. all was well until about 2 miles down the road and the bat light came on again. so i went to get it scanned at autozone. no codes came up and the bat checked out fine. guy said sometimes it take several cycles or drives to clean that light. i didnt think that was the case, yet no codes and all seemed to work well.

so today after leaving work with only about 8 miles since i changed the parts, the bat light comes on again. then the trans wouldnt shift past second, then the dash lights all came on. i drove into the parts store and it died. tried to recrank, and buzzzzzz, dead battery. i bought a new battery figuring i toasted the other one somehow and got a scan.

heres what pulled up.

p0622
p2503
p0700
p1684
p0562
p2100

is this something i can fix myself or am i screwed?

 

[flair1111]

one thing i need to mention, was a few days ago before i changed the parts out i noticed a burning smell. i assumed it was the belt getting hot due to a bad pulley on the alt. could this smell have been wires burning somewhere, and now its open causing the p0622 code?

now all the parts are new, and i still get the bat light. could i have a naked wire shorting out between the pcm and alt?

 

[renegade 04]

When the jeep is running see what the voltage is. It should be around 14.0 volts.

 

[tjkj2002]

P0562-system voltage to low


P0622-Gen field not switching


P1684-battery disconnected(no fix)


P2100-Throttle control motor(only for CRD's and '07 KJ's)


P2503-charging system low


P0700-TCM requests MIL turned on




You either got some really bad wiring,bad alternator(new does not mean it works right),or a bad PCM.

 

[Billwill]

I agree with renegade that you need to check the voltage across the battery while engine is running. Have you checked that the battery connections are clean and tight, the negative battery lead going to chassis is clean and tight both ends and the grounding lead from the engine to chassis is clean and tight both ends.

What year/model is your KJ? You sure you got the right part number alternator...2005/6 CRDs have built in regulators while other KJs have their voltage regulated externally by the PCM/ECM. If I know the year/model I can check the charging circuit diagrams for you.

Make sure the large connector on the alternator is clean and tight and make sure that the smaller plug on the alternator is clean and making good contact. I know on my Export 2002 CRD the large lead from the alternator rubs up firmly against a sharp metal bracket near the battery...I have added extra rubber tubing around the cable in this area to stop possible chaffing to ground!

With the battery disconnected try unplugging/re-plugging the connectors on the PCM/ECM as there may be a bad contact there on the voltage sensing line or the field control line to the alternator.

Putting a voltmeter over the battery should answer most of the above points...if the voltage stays the same while running as the battery voltage while turned off then there is a charge problem obviously....make sure the fusable link inside the large lead going from alternator to the battery has not blown...with ignition OFF you should read the same battery voltage on the large lug at the alternator as you do on the positive terminal of the battery if this fusable link is OK!

 

[k99jk99j]

the reman alternator market has alot of remans that aren't fit for sale. my first suspect would be a bad reman alternator. but i would try some more diagnosis first.

another thing you have to watch out for is the people that test alternators at these auto parts stores! just because you have a slip that says your alternator passed the test doesn't mean its a good alternator. you could have an intermittant problem.

 

[flair1111]

its an 06. ill have to wait until tomorrow to do a few tests. ill try all thats mentioned. i also suspect the alt, but i really wonder if the wire didnt burn up or the fuse blew as mentioned above. i did smell something burning before the light came on the first time. i just assumed it was my belt. the smell was accompanied by a very weird constant roar while driving home. the roar went away when i put the new alt on. ill post more after i run a few tests.

 

[libertybob]

Burning smell

Do Liberty's have a fusible link anywhere in the wiring harness?

 

[renegade 04]

yes, it is in the wire that goes from the alternator to the PDC.

 

[libertybob]

Fusible link

yes, it is in the wire that goes from the alternator to the PDC.

I would check the fusible link for the burning smell.

 

[renegade 04]

Your issue could be that the part of the ECM that controls the alternator field current is bad, and in that case you will need to wire in a old school voltage regulator like I did on mine.

 

[libertybob]

Voltage regulator?

Your issue could be that the part of the ECM that controls the alternator field current is bad, and in that case you will need to wire in a old school voltage regulator like I did on mine.

renegade 04, would you share how you wired in a voltage regulator to compensate for a bad PCM?

 

[renegade 04]

First thing you will need is a spare alternator connector, I got mine from a junk yard.
here is a link for that
Buy CARQUEST by BWD Pigtails & Sockets PT2042 at Advance Auto Parts
Next you will need the voltage regulator connector.
CARQUEST by BWD Voltage Regulator Connector PT65: Advance Auto Parts
You will also need to get the voltage regulator.
CARQUEST by BWD Voltage Regulator R400P: Advance Auto Parts
Next you will want to run a ground from the alternator to the case of the voltage regulator.
Next run a wire from a switch ignition source like the radio to the terminal labeled I.
Next run a wire from the alternator positive lug to the terminal labeled A.
Next run a wire from the Black/white colored wire on the alternator connector to Ground.
Next run a wire from the Dark Green colored wire on the alternator connector to the terminal labeled F.
As a side not you will not need to use the Terminal labeled S.
Also note that you will have the battery light on, but there is a part called a field replacement module for that.
http://alternatorparts.com/external-voltage-regulator-high-output-alternator-kit.html
Also note that this is for a FORD voltage regulator not a Chrysler voltage regulator.

 

[flair1111]

ok just cleaned all battery connections as well as the ground.

im just learning how to use a multimeter, so this is neat yet, im kinda lost. i got a little over 12 v on my new battery. cranked it, and got less. so i understand this shows no charging is going on. pretty simple.

i did a diode test on the negative bat cable to where it grounds at the body and it passed. i also checked from the main lug on the alt and also got the same v reading as the battery so i now know the fusable link is good.

so now, how do i bench test the alternator? and how can i diode test the small wire that plugs into the back of it?

 

[tjkj2002]

ok just cleaned all battery connections as well as the ground.

im just learning how to use a multimeter, so this is neat yet, im kinda lost. i got a little over 12 v on my new battery. cranked it, and got less. so i understand this shows no charging is going on. pretty simple.

i did a diode test on the negative bat cable to where it grounds at the body and it passed. i also checked from the main lug on the alt and also got the same v reading as the battery so i now know the fusable link is good.

so now, how do i bench test the alternator? and how can i diode test the small wire that plugs into the back of it?

Can't bench test the alternator since it is computer controlled(voltage regulator is part of the PCM).

 

[renegade 04]

Sounds like a bad alternator, If you get the new one and it does the same thing then you will need to wire in the a external Voltage regulator.

 

[Billwill]

ok just cleaned all battery connections as well as the ground.

im just learning how to use a multimeter, so this is neat yet, im kinda lost. i got a little over 12 v on my new battery. cranked it, and got less. so i understand this shows no charging is going on. pretty simple.

i did a diode test on the negative bat cable to where it grounds at the body and it passed. i also checked from the main lug on the alt and also got the same v reading as the battery so i now know the fusable link is good.

so now, how do i bench test the alternator? and how can i diode test the small wire that plugs into the back of it?

I am not with you when you say "cranked it and got less"....while the engine is cranking the starter motor draws a lot of current so you expect the voltage to drop over the battery...as long as it does not drop below about 10 volts which indicates a bad battery. if the engine starts and runs then you expect that the voltage over the battery will go up to about 13.5 volts which means it is charging.

I am not sure what you mean by "diode test"....this setting on a Multi meter is used to test diodes.
I think what you are trying to do is a "continuity" test which means that you set the meter to "Ohms"...touch the red and black lead together to check that you are getting 0 Ohms or very near to it...then you check the continuity or resistance between two points ie. the negative lug of the battery to chassis where you would expect next to 0 Ohms....the positive side of the battery would need to be disconnected at this stage as when testing for resistance there should be no outside current involved. you can then do the same procedure with this time the negative lead disconnected and check from the positive battery lug to the alternator. Neither of these tests prove much though because you are drawing next to no current through the meter....under the 600 A or so that the battery carries while turning over the starter motor then even a slight bit of bad contact on the battery clamps causes a major voltage drop there.
You need to check that you have a very good, charged battery.
The battery terminals need to be clean and tight...use sandpaper to clean the contact areas. Do the same with the contact of the negative lead to chassis and both sides of the grounding strap that grounds the engine to the chassis.
All that these steps will do is ensure that while the engine is cranking...there is not such a large voltage drop that the PCM only gets about 10 volts supplied to it so that it cannot function.
The PCM controls the charging voltage by Pulse Width Modulation on the field coil of the alternator.....in other words the one side of the field coil should go straight to +12 volts from the battery while the "ground" side of the field coil is switched On/OFF continously in PWM mode by the PCM...the PCM sends a square wave of negative voltage to the field coil in varying durations...the more time the pulse is negative...the more current flows....the PCM can under heavy load switch this lead to ground completely to get maximum charge from the alternator....this is how you can actually Bench test the alternator..supply +12 volts directly across the field coil to get maximum voltage out of the alternator!

Let me post up some circuit diagrams with some marked positions of what you expect to get on your meter....I am assuming the Jeep starts and runs but does not charge?

I also assume that this is a 2006 KJ with the 3.7 L gas engine?

Edit to add: I see that the 2006 KJ Gas model circuit diagram shows that on the field coil a Black wire goes direct to ground (via some connectors) while the Brown/dark green wire actually gets switched ON/OFF by the PCM!

Yet if you read the Theory of Operation that comes with the Service Manual that this circuit diagram is a part of they give the same explaination as I gave ie. that the Ground is switched ON/OFF....this is not new that there are major discrepancies in the Jeep documentation!

I am waiting to hear if this is a 2006 CRD or 3.7 Gasser before I post the diagrams with advice on what to check!

 

[uss2defiant]

he has a gas liberty.

 

[flair1111]

I am not with you when you say "cranked it and got less"....while the engine is cranking the starter motor draws a lot of current so you expect the voltage to drop over the battery...as long as it does not drop below about 10 volts which indicates a bad battery. if the engine starts and runs then you expect that the voltage over the battery will go up to about 13.5 volts which means it is charging.

I am not sure what you mean by "diode test"....this setting on a Multi meter is used to test diodes.
I think what you are trying to do is a "continuity" test which means that you set the meter to "Ohms"...touch the red and black lead together to check that you are getting 0 Ohms or very near to it...then you check the continuity or resistance between two points ie. the negative lug of the battery to chassis where you would expect next to 0 Ohms....the positive side of the battery would need to be disconnected at this stage as when testing for resistance there should be no outside current involved. you can then do the same procedure with this time the negative lead disconnected and check from the positive battery lug to the alternator. Neither of these tests prove much though because you are drawing next to no current through the meter....under the 600 A or so that the battery carries while turning over the starter motor then even a slight bit of bad contact on the battery clamps causes a major voltage drop there.
You need to check that you have a very good, charged battery.
The battery terminals need to be clean and tight...use sandpaper to clean the contact areas. Do the same with the contact of the negative lead to chassis and both sides of the grounding strap that grounds the engine to the chassis.
All that these steps will do is ensure that while the engine is cranking...there is not such a large voltage drop that the PCM only gets about 10 volts supplied to it so that it cannot function.
The PCM controls the charging voltage by Pulse Width Modulation on the field coil of the alternator.....in other words the one side of the field coil should go straight to +12 volts from the battery while the "ground" side of the field coil is switched On/OFF continously in PWM mode by the PCM...the PCM sends a square wave of negative voltage to the field coil in varying durations...the more time the pulse is negative...the more current flows....the PCM can under heavy load switch this lead to ground completely to get maximum charge from the alternator....this is how you can actually Bench test the alternator..supply +12 volts directly across the field coil to get maximum voltage out of the alternator!

Let me post up some circuit diagrams with some marked positions of what you expect to get on your meter....I am assuming the Jeep starts and runs but does not charge?

I also assume that this is a 2006 KJ with the 3.7 L gas engine?

Edit to add: I see that the 2006 KJ Gas model circuit diagram shows that on the field coil a Black wire goes direct to ground (via some connectors) while the Brown/dark green wire actually gets switched ON/OFF by the PCM!

Yet if you read the Theory of Operation that comes with the Service Manual that this circuit diagram is a part of they give the same explaination as I gave ie. that the Ground is switched ON/OFF....this is not new that there are major discrepancies in the Jeep documentation!

I am waiting to hear if this is a 2006 CRD or 3.7 Gasser before I post the diagrams with advice on what to check!

thanks for all the help. it is a gas 3.7 2006. and yes i meant a continuity test. it wasnt showing ohms or anything, just gave a beep if it was good. and i meant "when i cranked it i got less" i mean the voltage on the battery was showing less volts than before i cranked the engine. it didnt shoot up to 13 or 14, and its a brand new battery.still getting used to all the words and meanings. it seems i just need to pull the alt and go get a replacement. but id love to check more with the meter if i can so im not just guessing again. would be great to get it narrowed down a little more and have a reason.

 

[CactusJacked]

so now, how do i bench test the alternator?

Yes, contrary to unpopular belief, you can "bench test" the alternator. But instead of removing and mounting it to a bench, keep it mounted to the engine. What you'll be doing is called a full field test. There are 2 wires on the alternator plug, my year has a green and a tan/black stripe. One wire has battery power to it and the other is the duty cycle ground that gets activated by the voltage regulator in the PCM. Double check which is which on yours with the volt meter. Trace the ground wire (green in my case) back to the PCM and disconnect it there. With the engine running, touch this wire to ground, which will throw the alternator into a full charge mode, then see what your volt meter shows at the alternator. If your alternator is good, you'll be beyond the 14.5 volt neighborhood. If so, then you need to start suspecting you have a bad PCM, but that can be remedied (less expensively) by doing the aforementioned external regulator conversion.