2007 Jeep Grand Cherokee 3.0D mystery charging\CAN\overcharge problem

Hello everyone!
Just got my new "project", want to fix it and keep it, like that truck. but need some help\info

2007 Jeep Grand Cherokee 3.0D 4x4 - with electrical issues (it's what the previous owner said)

Story:
2-3 months ago guy used that truck, and at some moment he saw on the dash warning light "service 4x4", truck stopped moving, transmission stopped shifting, all dash lights was like "Fleshing Christmas lights". He dropped the truck at the dealership, The result of the dealer inspection - "damaged wires on CAN system somewhere, they ask about 15-18 hours (140$ per hour) to fix it..."  The owner decided to sell it for cheap...

When I checked the truck - scanned all systems, was a tons of codes for "No communication...." with  amplifier, steering control module, radio, ABS module etc.
I bought it and now it sitting in my garage   (was towed)

Now is my diagnostic story :
- The battery was low (10.9 - 11.4v) - so I charged the battery and cleared all codes in all truck modules
- Start truck - all dash lights are off for 4-5 seconds, after check engine light is ON (engine runs amazing)
- Scanned truck again, only one ACTIVE code in ECM - U1132 - Lost communication with generator
- Start truck - no charging from alternator at all - at battery terminals 11.2v, at B+ alternator terminal 11.1v 
- Checked all fuses\relays\wires on the charging system - all is good
- Checked data wire between ECM and alternator - good, no damages (Mercedes type alternator connection 2 wires - 1 fat positive wire to battery, 2 - data\CAN wire from ECM)
- Checked ground cables - all is good
-  Alternator was removed, found burning\melted\fire damage on the "brush holder"\voltage regulator
- New alternator was ordered and installed (reman)
- With new alternator code U1132 is gone. On idle charging voltage is 14.6  - 14.85 volts 

But..........
When I raise RPM to 900-1300:
- charging voltage jump to the 15.4 - 16.2 v
- warning message on the dash - "Service 4x4 system"
- error code in 4x4 module - Voltage to high
- headlight and cluster light (background) is momentary on (when voltage over 15.8v)


Steps after new alternator was installed:
- All aftermarket adds was removed - Viper alarm, Remote start, Aftermarket radio, Sirius FM module
- Just in case, tried to start with another battery
- ECM was removed and opened - no any visual damages\corrosion etc 
- Extra ground cable was installed (my wifes idea )

My ideas and next steps:
1. The voltage regulator in ECM is damaged, signal is controlled to charge the system 15-16 volts, hi voltage in the system engaged relays for headlights and cluster light, 4x4 module don't like voltage and shows code for "voltage too high"... - ECM needs to be replaced
2. Damaged wires - CAN wires shorted to ground or positive etc., ECM got the bad signal and controlled alternator charge system up to 16v, BCM got bed signal and turned on and off headlights and etc....

Need help with some ideas on how to test\check it right...
Becouse reman ECM - 1600 CAD 
Little bit confused...









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fbbt12, where did you get your reman alternator from? Asking because that's honestly my first suspicion. The aftermarket seems to struggle with this style of internally regulated, LIN controlled regulators.

First checks I'd suggest would be voltage drop between the positive battery post and the B+ stud at the alternator, and between the negative battery post and the alternator case. 

Second would be to unplug the LIN line (the single wire connector) and recheck for charging system voltage at idle and off idle. If the charging system voltage remains too high off idle, I'd argue that it cannot be the ECM. Only the alternator would be suspect at that point.

Third would be to check the ECM powers and grounds for voltage drop. It may be that one of the powers/grounds has high resistance, causing the ECM to incorrectly read system voltage and command the alternator to charge more than it should.

I would not be suspicious of the ECM or CAN lines at this point. The alternator gets its request to charge from the ECM on a LIN bus that is only shared with the glow plug module. CAN is not involved. The only way I could see that the ECM would request the wrong charging system voltage would be if its system voltage measurement was wrong.

Tyler gave you a good piece of advice. I would also look very closely look at the voltage sense inputs to the pcm. You will find the voltage seen by the pcm with a suitable scanner as well.

Service information states there are two of them, one from the alternator to C1, terminal 24 at the ecm, light blue color. The other one runs from the TIPM (C1/36) to the ecm(C!/12).

But nor the OE wiring diagram nor the redrawn one show them actually and the ecm connector pin out names different circuits there. It might be a glitch for the diesel engine because they do match for the gasoline version diagram??

Can you confirm this is VIN M vehicle and the on the diesel engine installed module (called ecm, contrary to pcm on gasoline engines) features two 96 pins connectors?

Thanks for your response guys. Some extra info it's great!

1. Altrrnator reman - from rockauto, reman company - BBB industries, on a box was "Wilson" sticker
2. Voltage drop test positive\negative was done - all looks good
3. Will try today to check the charging voltage with\without LIN connector on the alternator, and on different RPM
4. ECM power and grounds - will do the double-check today, just in case. But pretty sure all was good.
5. Damaged LIN\DATA wires was a "last chance" or "stupido" suggestion... I just start to think "outside of the box"
6. ECM voltage - used the AUTEL MS906BT - on live data stream 14.8 on idle, 15.8 - 16.2 on hi RPM
7. About wire diagram - one WH\BL wire from the alternator goes to Glow Plug Control Module (GPCM) on pin 12 and after goes to ECM on pin 88 - wire is good, resistance is 0, no any drops to power or ground
8. 2007 Jeep Truck Grand Cherokee 4WD V6-3.0L DSL Turbo VIN M - have access to AllData

Yesterday had a chance to take a waveform from ECM pin 88 on idle with connected LIN to the alternator - The signal is not really good, big gaps, and jumps up to 15-16 volts will try today to connect the oscilloscope and get the waveform on hi RPM and disconnected alternator + disconnected GPCM...

Thanks guys
Will keep this topic updated


 

tried to add pictures... 

https://ibb.co/9Wnrk2w

ibb.co/9Wnrk2w

to much voltage could damge your glow /p module or might need reset GOOD LUCK

Done!!!

After tons of hours and 1 case of good beer in the garage, all is DONE and FIXED!

In total
I was able to find used ECM locally for a cheap. My Autel MS906BT has a function to change VIN and odometer in used ECM.

ECM was installed and "reprogramed" - start truck, the voltage on idling drops down to 14,6 - 14,7 volts, but on 1300RPM still overcharges - 15.2-15.5v
But with the "new" ECM charging voltage dropped a little bit and the live data was different as well - The "battery voltage set" dropped from 15.02v to 14.92v

Next step - "reman/new" alternator (BBB industries from Rockauto) is garbage. Was able to find OEM alternator from Dodge Sprinter - the same engine. (scrap yard)
Installed "new\used" alternator - start truck - WooHoo! Idling - 14.3 - 14.4v, 1300RPM - 14.5 max! Tried to add loads - heater, lights, etc - all is good! charging shows - 14.3v!

Decided to connect the "old" ECM and check the voltage with the "new\used" alternator - idling 14.8 - 14.9v, 1400RPM - 15.1v, and big misfire at acceleration! 

Called the previous owner and asked about any repair info, long story short - his mechanic replaced the alternator, and they got parts from some online store with a 90-day warranty because a good brand costs nearly 330-430$. From the factory it should be a 180-amp alternator, they installed a 220-amp "no name \ chinizium" part. I think that was a point when the alternator started to overcharge the system and damage ECM with hi-voltage... 

Thanks to all who shared some ideas here! 
Happy holidays!

Thanks for the feedback.

GOOD JOB !!!