P0622 charging system fault 2004 Taurus 3.0 Vulcan

[Witsend]

My nephew had his alternator go out and my brother jumped the car let it charge up for awhile and managed to get it back to his house and had me get a rebuilt alternator for it, which he was able to put in himself, but called me back and said that the check charging system message and battery light came on yet his cheap voltmeter said it had close to 15v.He ran it to Advance auto and the charging system tested ok, but figured the reman alternator still had a problem and he drove it to me. I hooked up the scope and the alternator pattern humps looked pretty ragged looking at idle , but appeared nice and rounded at higher rpm (divide waste spark rpm in half) Voltage drop tested cable from alternator to battery, the ground from the alternator case to the battery negative post, the circuit from fuse 26 to 3 wire connector and continuity of the 2 wires from the alternator to pin 20 and 45 of the PCM and all seems good . I ordered another cheap used PCM after getting a good used alternator from the salvage yard that charged but did not resolve the charge warning and battery light that comes right back on after running a minute or two.

[Witsend]

Did A Doodle Google

Came across this Revelation Gem of information that sounds promising. The reman alternator(that I have not returned yet) tested within the desired Ohm specs from Pin 1 to the case at room temperature, but I will check the used one I have on the car while everything is hot and test the resistance of pin one to the case at operating temperature on the vehicle.

http://troubleshootmyvehicle.com/ford/4.6L-5.4L/ford-p0620-alternator-diagnostic-test-1

[Witsend]

Well I ohm ed out pin 1 on both alternators but they both were in around 1.2K ohms within range that the internet article tech said is ok , so I ordered a used $42 dollar ECM off Flea Bay,received it and following week, got the car back and installed it and programmed all the immobilizer keys with Port Freight 08 and car started. I cleared KAM and trans tables and then go to drive it and the charge system warning and battery light is back on within minutes. Looks like,logic dictates I do a pin out check of all the power and grounds for the PCM (besides the charging system circuit checks I already did earlier ), then I'll have to test the data bus wires from the PCM to the back of the instrument cluster.( saw another Bogus Port Freight 08 description for instrument cluster code B1208 and a Rosa Parks code (Bus communication error) If i don't find a wiring issue , it looks like my brother's Instrument cluster with 136K gonna likely have to be swapped with another cheap salvage used part that likely read mileage over 200K .

[Witsend]

Well , pulled the radio , HVAC control, finish panels and cluster. Called the dealer and was quoted $478 for a replacement instrument cluster, and was told the part # by look up from VIN # that the replacement # is shown for just 2004 model year. No 2004 models presently are at the local salvage yard. On Flea Bay going by faded label #a used one listed with 78K miles for $62 with the same sticker number as the one I pulled but and that # is listed to work for both 04 and 05 model years.
Well the Salvage yard has one 2005, but they don't know the mileage . Well for U-pull it $20 and a $5 core, nothing ventured, nothing gained, I drive the Taurus to the yard with no instrument cluster installed, taking my jumper pack and a few tools. I hook it up a jumper pack to the salvage yard battery cables and see interior lights, and message on cluster about LF door ajar ,Look for ignition key and find it inside the trunk , close the door and turn the ignition key on and the odometer displays less than 93K. Very Cool, and low mileage. I actually lower the column which made removing the cluster easier. Pay only $27.50 with tax and no core return out the door , plug it in and everything works on the used cluster fine for about a minute driving out of place , and then the dreaded Check charging sys message and battery light came on.WTF!
Screw it, my brother can get the $5 core cash and $22.50 credit.
I tested all the wires and fuses again in the charging System wiring diagram, tried a used PCM ( requiring keys programmed ), tried a cluster, verified the 2 CAN wires from PCM to cluster. I'm running out of ideas here Crazy sh@t, it's charging fine, PCM is splitting hairs and comparing the #of humps in the voltage to the rpm and doesn't like what it sees ? Looks like I just got to verify the remaining PCM and cluster ground and power supplies before trying another alternator

[Witsend]

Well after 10pm and some cold ones, I decide to go outside and test all the power and grounds to the PCM and instrument cluster and all checks out. I put the original PCM and cluster back into the vehicle and now none of the 4 PATS keys will start the vehicle.
Tossed a charger on it, wait for security access and luckily able to Erase and reprogram all the keys back again to original PCM and start the vehicle .Strange thing before PCM was removed I never erased the PATS keys from the original PCM and thought the chips in the keys stay the same and codes would be in there and work unless I erased all the key codes from the PCM and therefor it could make a good working redundant spare PCM.
So I am pretty much back to where I started, trying another alternator. Got to write myself a letter , and fire myself on this one.

[Witsend]

Went to the salvage yard today and grabbed the alternator from the 2005 Taurus I got the instrument cluster from. I was hesitant to install it because Pin 1 was basically reading open loop with the positive DVOM lead on pin 1 of the rectifier and the negative lead to case and about 12 Mega ohms with the negative DVOM lead on pin 1 and the positive lead to the case, but I installed it and it charges at about 1 volt lower than the one I removed but the PCM is in more control of the regulation now, not the regulator doing things on it's own.
The scope attached to pin 1 displays a nice square wave duty cycle now , where before I thought it was flat lined somewhere around 5 volts. Sure feels good to get that turd out.

[ralleman]

Hi Witsend
What is that 08 tool you keep mentioning ?

Thanks
Rik

[Witsend]

It's what I call the old Autel DS 708 because you can buy one at Harbor freight For less than the nine ninety nine Earl Chive paint job