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Mazda Ed
Mazda Ed, Auto Service Technician
Category: Dodge
Satisfied Customers: 2223
Experience:  ASE Master Technician, Mazda Master Technician, GM and Ford factory trained. 15 years experience.
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2000 Dodge Durango: 4X4..the battery, alternator (new) & PCM module

Customer Question

ok, here is a good one. 2000 Dodge Durango R/T 4X4, code p622 & P1682. Replaced the battery, alternator (new) & PCM module and tested the system with a DVM. Seems to only happen after the SUV sits after driving, engine compartment temp increase.

Here is what happens, Before I replaced all the above the car would just shutoff while driving at low speeds after sitting hot or on a extremely hot day, once the car was moving on the freeway it seemed to work fine. When the car stopped it would crank but not start for up 20 minutes, then it would run for a few minutes (unless you got on the freeway immediately). So, I assumed that I had a bad PCM, it was getting very hot. I replaced it. After that I started to get the "Check Gauges" light (I had never seen that light in all the years I have owned the car) and the volt meter was dropping slowly to "0", however the car continued to run. Shutting off the ignition and restarting cleared the the light and the voltage came back to 14 volts. I tested the voltage output of the alternator and it was 13.8 to 14.1 volts. So, I assumed (we know what that means) the I possibly have a diode in the alternator that is going south when it gets hot, replaced the alternator. Same issue following the replacement of the alternator. I drove it home and tested the voltage output from the alternator while the issue was happening and it was normal, 13.8 to 14.1 but the gauge on the dash said "0" volts. Not sure where to look now. Any ideas?
Submitted: 6 years ago via CarComplaints.com.
Category: Dodge
Expert:  Mazda Ed replied 6 years ago.

HiCustomer

 

The codes are as follows:

P0622 - GENERATOR FIELD NOT SWITCHING PROPERLY

P1682 - CHARGING SYSTEM VOLTAGE TOO LOW

 

So obviously something is not reading correctly in the charging system.

 

Where did you test the output of the alternator? Was it directly at the alternator or at the battery?

 

Customer: replied 6 years ago.
directly on the alternator with a Digital Volt Meter
Expert:  Mazda Ed replied 6 years ago.

Great, can you check at the battery also?

 

Also measure the voltage between the battery + and the generator output terminal.

Customer: replied 6 years ago.
It is a new battery (FYI) and the battery voltage at the battery is the same as the voltage at the alternator + terminal. I think the clue is the restart, just by shutting off the vehicle and restarting it clears the message and the Dashboard voltage returns to normal, you think?
Expert:  Mazda Ed replied 6 years ago.

Slow and steady wins the race here :) Lets just step through the diagnosis to see where we get.

 

Disconnect the PCM and the generator to measure resistance on the two wires shown below. Measure from end to end and then from one wire to the other. Finally measure from each wire to ground. Let me know the results. You must test when the vehicle is experiencing the problem.

graphic

Customer: replied 6 years ago.
Ok, sounds good. I will do this tomorrow and hopefully get this thing to happen again. What should the normal readings be?
Expert:  Mazda Ed replied 6 years ago.

Neither wire should have continuity to the other one and neither wire should have continuity to ground.

 

From end to end should measure close to 0 ohms.

Customer: replied 6 years ago.
One more question, are the 2 wires at the top of the diagram the 2 wires that plug into the alternator?

And are the 2 terminals on the PCM ([10]C2 & [25]C3 on plug 2 and 3 respectively? Color codes?

Thanks
Expert:  Mazda Ed replied 6 years ago.

Yes they plug into the alternator/generator.

 

Connector 2 pin 10 is a dark green wire (DG)

 

Connector 3 pin 25 is white with a dark blue stripe (WT/DB)

Customer: replied 6 years ago.
Thanks Ed, will let you know....
Expert:  Mazda Ed replied 6 years ago.
Roger that! I'm off to get some rest and will look for you tomorrow.
Customer: replied 6 years ago.

Ok Ed, I took the vehicle out for a hard drive and could not make it do the exact same thing but I did notice that the voltage was low, 12.04. So I did your checks as requested and found that the continuity was fine and the line to grounds were at infinity Ω's

I thought I would check the battery sensor as well and found it to be 220k to 240k Ω, seems a little high to me but I do not know the normal values. In addition I noticed that the battery voltage never changed while the sensor was disconnected and the charge rate remained at 12.04VDC. The engine off voltage of the battery is 12.48

After doing the checks I reconnected the PCM and the batter sensor and restarted the vehicle and the system came back to normal, check engine light cleared (from disconnecting the sensor) and the error codes cleared as well.

If as I stated in my original post, the output voltage at the Alternator was 13.00 +/- when the dash gauge indicated "0" wouldn't this indicate that the PCM control for the alternator is functioning correctly? Your thoughts?

Customer: replied 6 years ago.
An update Ed, this morning the dash voltage was @ 12 volts right off the bat. About 30 seconds of driving the voltage on the dash meter goes to zero and the "check guages" light comes on with the check engine (which is on all the time now). I continued to drive the vehicle about 15 miles to work this morning. Restarting the car did not correct the problem. I may or may not make it home.
Expert:  Mazda Ed replied 6 years ago.

Yes, I was thinking the alternator is being commanded correctly, but the signal is not getting back to the PCM.

 

If the voltage is 14 volts at the alternator but 12 at the battery, that has me concerned. Did you remeasure the voltage at the alternator when the battery was only reading 12V?

Customer: replied 6 years ago.

I made it home. The battery voltage is decreasing, the alternator is not charging, it was 11.8 vdc when I got home. So, I re-did the checks you sent and all was fine as before. I decided to hook up my volt meter to the battery and start wiggling wire harnesses and BINGO the C2 connector on the PCM apparently has a bad connection, (probably on pin 10). The alternator started charging. I took it out again for a test ride and AGAIN the voltage dropped to "0", I turned around and went back home and with the engine still running and the volts at zero I tested the battery with my DVOM, 11.7 volts. Then I moved the C2 connector and I could hear the alternator started working, the volts went to 13.7. Shut everything off and removed the connector and the wire cover to the back of the connector and closely inspected all wires and pins, no apparent loose or broken wires. Sprayed some contact cleaner on the connector and reassembled. Fired it up and went for another ride, 10 minutes into it the voltage dropped again, this time I shut the engine off and restarted and it came back to 14 volts and stayed there for the remainder of the trip home again. I will see how it goes tomorrow, but I am suspecting a pin problem on the PCM...

Expert:  Mazda Ed replied 6 years ago.

Glad you made it home!

 

Before you blame the PCM as the culprit, make sure the pins in the connector didn't get spread open when you were checking the resistance. I use special adapters to check the terminal tension. Without these, you will have to fabricate something that looks about the size of the PCM pin. Then use this tester to see how much drag is on a couple of the good pins. After that compare the drag to the suspect bad pin.

 

If everything checks out ok, you may be able to open up the PCM and resolder the connections. I have fixed a few PCM/ECMs this way. Yours might be screwed and glued which will make it harder to open.

 

If you do decide to get a used PCM, let me know your zipcode and I will see what is available near you.

Mazda Ed, Auto Service Technician
Category: Dodge
Satisfied Customers: 2223
Experience: ASE Master Technician, Mazda Master Technician, GM and Ford factory trained. 15 years experience.
Mazda Ed and 2 other Dodge Specialists are ready to help you
Customer: replied 6 years ago.
Thanks again Ed, I will leave this open for a few days and let you know the final and then close it out and accept the answer with positive feedback... My Zip is 92562

Again, thanks
Expert:  Mazda Ed replied 6 years ago.

To make sure I locate the right PCM, this is a 5.9L right? Also, is it federal or calif emissions? It would say on the label under the hood.

 

Just so you know, even after you accept and leave feedback you can return to this question.

Customer: replied 6 years ago.
VIN 1B4HS28ZF243312 California and indeed a 5.9L
Expert:  Mazda Ed replied 6 years ago.

Ok, here is the list of what I could find. I have dealt with Don's in Binghamton NY on several occasions and they always treat me right. Only ever had one problem when they shipped a headlight for a different vehicle.

graphic

 

Ok ,off to bed.. keep me in the loop until this is 100% solved!

 

Customer: replied 5 years ago.
As a final followup on this: The problem was the ECM, the charge control circuit electronics were going crazy when the ECM got hot.

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Mazda Ed
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ASE Master Technician, Mazda Master Technician, GM and Ford factory trained. 15 years experience.