thoughts

Did you replace wit a NEW alternator?
did you disconnect all alt wires or just the 2 small (felds) wires?
Maybe check the diodes - a simple AC voltage check on alt wire. Leaking diodes skew the speedo & tach signals.
What if any codes did your scanner show?

 

Yes, i bought a brand new (aftermarket) alternator. The old one was charging good, but I thought maybe something was wrong with it anyway. So I got a new one, but it didn’t help.

Unplugging the two field wires (small connector) makes everything ok. I did a final test before going home just now, it’s still the same. Plugging it in and the fault returns. I loose every gauge, and every light comes on.
I’m thinking it must have something to do with the charging circuit in some way. The diodes should be ok on a new alternator.
I haven’t checked the fault codes yet. I only have a cheap obd scanner, but a friend of mine has a more professional system, I’ll ask him to help.

 

Btw… i have a parts car available. It’s the same engine, one year newer I think. Can I try the pcm from that car or will it require programming to work?

 

Thoroughly check the wiring between front doors and body on both sides. Remove the rubber boots and check wire by wire

 

I have done that, it seems ok. I know thats a common issue. But with only the ignotion on, everything is working, all Windows, locks, mirrors, everything. Also with the engine running and the plug at the alternator disconnected. Everything ok.

 

I do NOT recomend swapping PCM's .

The cades will help, the 2 small field wires we can check- do you have a DVOM ?

 

I do NOT recomend swapping PCM's .

The cades will help, the 2 small field wires we can check- do you have a DVOM ?

I did ohm the two field wires, found them at connector two and three at the pcm, and they were ok. Did not measure anything else.
I will recheck the charging voltage. I’m sure it’s not too low voltage, but thinking if it could be too high? Where do the pcm get the voltage input from? I can hear the alternator working, and it gets pretty hot very fast.

 

Very common problem I see with these in the shop, the pcb fails at the voltage regulator in the pcm and this is exactly what happens.

Your spare pcm should get you fixed up, you'll need to find a Tech that can flash it for you.

 

Very common problem I see with these in the shop, the pcb fails at the voltage regulator in the pcm and this is exactly what happens.

Your spare pcm should get you fixed up, you'll need to find a Tech that can flash it for you.

Is there a way to verify the problem on the pcm? I’m in Norway, and finding someone to flash it here may prove to be a challenge. I have no guarantee that the other pcm is good.

 

Look in the Jeep Liberty forum.

 

Changing the PCM on 3.1 TD is a bit more challenging than on gas WJs.
This piece of engineering has separate Bosch ECM which controls only the engine and is located under the rear seat and the PCM under the hood controls the rest. Both talk via bus.It has also SKIM nd its tied to both of these. Plug and play preprogrammed PCM not always works and in many cases you need a PIN code and DRB III to match the VIN. But its worth a try.
You can use an external regulator for alternator. It will work, will charge, but PCM will not know that and you will have some codes in the memory. If only the regulator is faulty and the printed circuit board inside is not toasted, it can be replaced. If anything else fails i have at least 3 or 4 3.1 PCMs lying here on the shelf.
Where in Norway are you located? My friend does NO, SWE spedition on a regular basis. Or GLS shipping is also not that bad.

 

Hi,

I just bought at 1999 WJ 3,1 diesel. I got it cheap as there were a few issues with it. Everything is now sorted, except an electrical issue which is driving me crazy.

To describe the problem, when starting the engine, everything is OK initially. Then the tach needle drops, then every other gauge drops and all the warning lights come on. It still runs. I also loose the window and door controls, overhead display and so on.

I have done a few checks already, I've checked the two connectors inside the passenger kick panel, all the ground points I could fine and so on. Then I found a guy on youtube with exactly the same issue, he changed the alternator and everything was OK.

So I tried to check a bit more, it turns out that if I disconnect the connector at the alternator, the plug with the two wires, everything is OK except the charging. It starts and runs as it should, all gauges OK (a little low on battery gauge naturally), no warning lights and nothing else. Windows and doors are working.

SO... I ordered a new cheap alternator, but the fault remains the same. Unplug the connector, everything is fine. Connect it, and the fault returns. I'm at a loss here.

I took off the connectors at the pcm, and ohmed tthe two wires from the alternator to be sure that they were not broken,and they were OK. Plugged in the connectors again, put on the battery negative and started. The fault is now somewhat different! There was no corrosion on the pins, but I took them off a second time and put some electric spray in there, and reconnected. Then I quit for the day. When I started the car to drive it out of the workshop, it all seemed to work for just a little longer, before the fault came back. But this time it still was a bit different. But the solution is still right, if I unplug the plug at the alternator and start it up, everything is OK!

Can anyone please tell me whats wrong here??

Regards
Stefan

check for short on the electrical distribution box that holds all fuses and relays. check all door to body wiring to see if you have any possible shorts there. is it only when you have it in gear, and moving ? check all relays and the power going to each relays. is there and after market radio or power amps for radio? if so pull that in line fuse see if you have any issues after that is cut out. check all after market lights. look close for any issues with suspension and wires including trailer lighting,,,,good luck. i notice with my jeep if my battery is no good i have all kinds if issues....

 

This happens as soon as I start the engine. With only ignition on everything is OK. When starting the engine, oil pressure reads zero, within a few seconds, first the tach needle drops, all the other gauges drops down, and all the warning lights come on. I also loose door locks, power windows, the overhead display, stereo, heater and so on. If i stop the engine, remove the field connector on the alternator, and start it again, everything is OK. I got oil pressure, all the gauges are working, all warning lights go out as they should, doors and everything else works as it should. The only thing not working perfectly is that the alternator doesn't charge, as it has no field voltage from the pcm. The car looks pretty original, original stereo, and nothing looks to be added on. No aftermarket lights or anything. It has about 281000 km so it has been around for a while.

I will recheck the charge voltage (overcharging?) and pull codes today.

 

SK jeep
Could your description refer to STYER built WJ's AND a different wiring?


Attached 99WJ 3.1L. Jefferson plant USA.

 

SK jeep
Could your description refer to STYER built WJ's AND a different wiring?

@jtec
Basic wiring (except engine and EU spec lights ) is the same. Does not matter if Jefferson North or Steyer. The engine controller is kinda piggybacked to the US standard WJ.
Bosch ECM receives some signals directly from the engine mounted sensors and controls the inj. pump. Other signals are routed to JTEC+ PCM and shared with Bosch ECM via PCI bus
3.1TD was made from 99 to 2001, where (at least as far as i know) almost all MY 99 were made in the USA, Jefferson plant.
The 3,1TD lasted only 2 years , for MY 2002 It was replaceed by Mercedes Benz OM612 2,7litre inline 5 turbodiesel

The 3,1TDits a modular design engine - 3 to 6 cylinders with separate cyl. heads, made by italian VM Motori, that time majority of stake owned by Chrysler, 4cyl
2,5litre version used in XJ cherokee, ZJ Grand, GS minivan..... so it was quite a logical choice.
But it was sort of a "hot needle" design. Europe wanted diesel, 3,1 was the 1.st available for Chrysler so they went on.
Poorly mated to slowly obsolete A500 (44RE) auto trans using an adapter prone to cracking, software issues in design, lockup engages at speed of +103 km/h, because of a software error when converting miles to kilometres plus dozen other issues.....

 

skjeep is well versed in the 3.1L - i did not know of the separate bosch controller (ECM) interesting set up here.

But I read the PCM controls generator (AKA alternator) same old jeep set up.

What happens if you remove the large wire from alternator, does it act up with field plugged in ?
I am thinking a simple field wire check,
KOEO -connector unplugged check that one wire is battery voltage, the other has NO voltage.
KOER - still unplugged are the readings the same?

 

Quote "If i stop the engine, remove the field connector on the alternator, and start it again, everything is OK."

How do you fancy the idea of an external alternator regulator Gaffer?

 

my thoughts are
1) testing field wires - a short could cause full field OR if the signal 12v wire is shorted to ground could it cause problems as PCM is shorted?

2) the large wire is open between alt and battery and shorted to ground - the field causes the alt to charge right to ground.

 

my thoughts are
1) testing field wires - a short could cause full field OR if the signal 12v wire is shorted to ground could it cause problems as PCM is shorted?

2) the large wire is open between alt and battery and shorted to ground - the field causes the alt to charge right to ground.

I tested the field wires, ohmed them between the connector at the alternator connector and the connectors at the pcm, they are ok.

With the connector on and the engine running the charging is fine, about 14,2V at idle, but the fault is present. Disconnecting the connector at the alternator everything is oK except the charging.

It would be interesting to see if "fooling" the alternator to charge with the connector off, would set off any faults or not.

 

I can't remember -
Have you looked at alternator DIODES - simple AC voltage check.
with ALT all plugged in - engine aat idle - probe field wires, 1 should be battery volts other will be @3 volts less. post if different.
Did you check codes?

 

Here's another alternator check for you St.

Turn off all accessories.
Remove plug at the back of the alternator.
Connect the male blades in the socket to your battery live.
..............3.2mm female blade connectors
..............exactly fit the males in the socket
Start engine.
An okay alternator will give you around 17v.
Turn engine off.

 

A thought - waterluver is the PCM go to member and he suspects a PCM issue. Pay attention.
Me I hate to condemn a PCM without testing and more testing.

I would unplug alt field wires, use a test light to jump the connector terminals, at idle the test lght should come on and flash. question is Did the engine act up or run smooth?

Thinking here is separate PCM from ALT and test the PCM driver alone.

 

A thought - waterluver is the PCM go to member and he suspects a PCM issue. Pay attention.
Me I hate to condemn a PCM without testing and more testing.

I would unplug alt field wires, use a test light to jump the connector terminals, at idle the test lght should come on and flash. question is Did the engine act up or run smooth?

Thinking here is separate PCM from ALT and test the PCM driver alone.

Waterluver does not deal with non -US PCMs Jt.
I can't remember exactly, but I think massive tax costs
and stuff getting lost in the post put the mockers on it for him.

 

OK, thanks guys! A bit on and off here, work and stuff..

But: Regarding alternator, i must assume that the brand new alternator is good, with no broken diodes or anything. I base that on the fact that the old one was charging, the new one is charging, and there is no difference at all with a brand new alternator.

I haven't tried messing with the field connectors on the alternator, I'm a bit hesitant to put 17 volts at the electronics. With my luck, something else would break from over-voltage. However, it would be interesting to see if I put a variable amount of voltage at the alternator, to get it to charge, if the car acts up or works fine. I know that with the connector installed, it charges just fine at about 14,2V. But the faults are there.

Disconnect the field connector at the alternator, it doesn't charge but no faults what so ever.

The engine doesn't act up in any way, it runs both with the connector removed and faults gone, or with everything connected and also faults present. Runs and drives.

I did try to get the codes, but not successfully. Both the expensive Wurth tester and the cheap ebay obd reader did not connect to the vehicle. The key on/off trick didnt work.

There is a US car workshop here, if anyone can pull the codes, he can. But I don't know when he gets around to it.

So, still any input much appreciated!

 

For codes no connection to scanner -

first thing to check is cavity 16 of OBD connector - should have 12v KOEO.
At every start does the CEL come on for @2seconds then go out?

I'd like to like to regroup -
"it charges just fine at about 14,2V. But the faults are there."
what are the faults?
How does jeep run - what issues when alt plugged in -

The 2 last test I suggested - reply 27 above.
The Alt diode test is a fast easy - just set DVOM to AC voltage clip on batt terminal of alt with eng at idle.
The other test to bridge the alt connector with a test light - EASY FAST

My thinking -
" i must assume that the brand new alternator is good, "
ASSUME acronym guessing makes an *** of U and ME

 

For codes no connection to scanner -



I'd like to like to regroup -
"it charges just fine at about 14,2V. But the faults are there."
what are the faults?
How does jeep run - what issues when alt plugged in -

The 2 last test I suggested - reply 27 above.
The Alt diode test is a fast easy - just set DVOM to AC voltage clip on batt terminal of alt with eng at idle.
The other test to bridge the alt connector with a test light - EASY FAST

My thinking -
" i must assume that the brand new alternator is good, "
ASSUME acronym guessing makes an *** of U and ME

I’ll check the obd connector next time I get around to work on it🙂

To regroup:
When I start the car with everything connected, like it should be, it starts out as normal. Glow process is a few seconds, then it can be started. After starting, oil pressure gauge does not work. Then I loose tack, and the other instruments follow, as well as all the warning lights come on. I also loose functionality of the power windows, overhead display and a few other things. Charging is good at 14,2v but the gauge is dead.

if I stop it anddisconnect the plug (field wires) on the alternator, I can start it up like normal. Every light come on initially, also CEL, then goes away, like it should. When the engine starts, I have normal oil pressure, all the gauges are working, all the warning lights go out one after the other, doors/windows, stereo, everything is like normal. Voltmeter in the instrument cluster shows about 12v or thereabout, as the alternator is not charging. But everything else is normal.

 

Is there a way to put a video in here?

 

If you run a diesel this will do the business for you: -
V17.04.27 wiTech MicroPod 2 for Chrysler Diagnosis & Programming Multi-language

 

Does this manual take you where you wish to go please Sk?

Jeep Grand Cherokee WJ. Manual - part 591

P591 "On the following pages, a list of DTC’s is provided for the 3.1L diesel engine."

 

FOCUS - we are straying off the reservation

Issue - is alternator when field connected sy-t* happens.

* oil pressure gauge does not work. loose tack, other instruments follow, all the warning lights come on. loose functionality of the power windows, overhead display and a few other things.

 

FOCUS - we are straying off the reservation

Issue - is alternator when field connected sy-t* happens.

* oil pressure gauge does not work. loose tack, other instruments follow, all the warning lights come on. loose functionality of the power windows, overhead display and a few other things.

Thanks Jt

 

My thoughts / my 2¢ try to ID what could be the cause of issues. divide and conquer.

PCM controls the ALT field - So seperate ALT from PCM -find out which one is causing issue.
Simple fast and my favorite FREE,
A test light into alt connector HARNESS side, then jump terminals, enough of a load that PCM will ground field.
1) no change the system stilll goes to S**t. suggests PCM is cause

2) system works good none of the issues - Suggests ALT is cause.

And we get a focus point..... and I can get back to bourbon sampling.

 

My thoughts / my 2¢ try to ID what could be the cause of issues. divide and conquer.

PCM controls the ALT field - So seperate ALT from PCM -find out which one is causing issue.
Simple fast and my favorite FREE,
A test light into alt connector HARNESS side, then jump terminals, enough of a load that PCM will ground field.
1) no change the system stilll goes to S**t. suggests PCM is cause

2) system works good none of the issues - Suggests ALT is cause.

And we get a focus point..... and I can get back to bourbon sampling.

My thoughts are still to connect the alternator to an external controller Jt.

What reasons have you against that route to divide and conker please?

 

The external controller is LAST ditch if PCM is the problem child.
That will set codes for field circuit, although I have heard there is a work around .

I am thinkinh 1st determine what is cause o f problem PCM or ALT.
And I think my test idea is faster than time to reply , and yeah I am old and slow.

 

Thanks Jt

The man who sells the external controller I posted earlier can provide a work around where it's needed.

 

OK guys, this problem is solved!

I had to get the car to a amcar specialist shop with the proper diagnostics tools. Turned out the fault was the PCM. I had a spare one, which they programmed and that solved all the problems.

Thanks for all your input, it was a puzzle.

 

Thanks Stef

I bet you feel as pleased as a pig in clover now don't you?