Lincoln LS Charge system and PCM problem. Help!

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vktrenz

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I currently own a 2000 Lincoln LS. My battery died and wanted to start it back up again. I increased the amps and boosted the car up. Before the jump and before the battery died. I had no "Check Charge system light", but right after I jump started it. The light came on, and I checked the voltage. It showed me 13.3V. I changed the battery and the light was still there and still 13.3v. I changed out the alternator 4 times and same problem and same 13.3v on the battery and the generator when the car is running. The voltage regulator is on the alternator and it still shows 13.3v. I added another ground and cleaned positive and negative leads. traced wires and found nothing. So I decided to unplug the alternator plug on the alternator it self. after doing so I check the voltage and it showed me 13.8-13.9v! I was surprised, but once you plug the alternator plug back on. It reads 13.3v again. I bought a new pcm and take the car to the dealership to be programed, and the programing fails. I find out I gave them the wrong pcm. I was not compatible with the serial numbers. I brought the car running, and when they tried to hook up my old pcm, the car doesn't start. Dealership searched and searched and could not find what the problem is. They checked everything from fuses to solenoid to tracing wires, and came up nothing and said they cant find or don't know what to do next. Now my only option left is to get a new pcm with the right serial number and try again with the programming. My question is this, if I put to much amps from a jumper box could I burn the pcm? Or any other ideas?? Thanks
 
The current from your booster/charger isn't really a factor. The factors are the maximum voltage and how well rectified and filtered it was. If the voltage went over 16 volts and/or was poorly filtered, you could have damaged the PCM. If this was a cheap charger/booster or fairly old, then the chances are that it is not well filtered and does not have protection to keep it from going over 16V.

All that said, it sounds like the dealership may have killed the PCM.

The alternator sort of has a built-in regulator, but the PCM actually controls the alternator and sets the regulation voltage. It sounds (from your description about unplugging it) like the replacement alternators were not the OEM Motorcraft one. That would explain why none of them worked correctly. The gen I LS does not work with most (maybe all) aftermarket alternators because they often have built-in non-PCM controlled regulators. You will have to replace it with the OEM part.

You will likely need to replace your battery too.
 
Yeah that is what im thinking, I think I burned it first. I wanted to start the LS fast instead of waiting for the battery to charge up. But I looked and did research, I thought is was the alternator, but it wasnt. I had 1 aftermarket alternator and the rest were oems. They werent cheap. Then as the last resort I got a new battery. So last option is try a new pcm and hope for the best.
 
Which alternator did you attempt unplugging the regulator on? If it was an aftermarket, non-OEM, then chances are the voltage regulator is not compatible; hence, the communication for the PCM is no longer an issue and the alternator is doing its own regulating. If you unplugged it with a Motorcraft alt, then that's a good indicator your PCM is cooked.

Like Joegr said, the PCM is more than likely shot. The cost of having one programmed isn't insane so your best bet is to get a matching serial, like you said, then a OEM reman alternator. That way nothing is in question.
 
What's the best path to replacing all three items without one ruining the other?

Say you don't want to have the dealer install the alt and battery and charge $400. Would you have the PCM flashed, then replace the other two or vice versa?
 
Replace the alternator and battery first. You might also be able to replace the PCM yourself. No idea if the Lincoln requires the car to be present to reflash the PCM, if it does you'll have to tow the car to the dealer and if not you can just take the PCM and your VIN to the dealer for a standalone flash. If you tow it in, don't even connect the battery. Let the dealer tech connect it when he reflashes.
 
Telco said:
Replace the alternator and battery first. You might also be able to replace the PCM yourself. No idea if the Lincoln requires the car to be present to reflash the PCM, if it does you'll have to tow the car to the dealer and if not you can just take the PCM and your VIN to the dealer for a standalone flash. If you tow it in, don't even connect the battery. Let the dealer tech connect it when he reflashes.
Click to expand...

Nope. The whole car has to be there (or at the very least the cluster, the keys, and the PCM). They "marry" the PCM to the dash cluster. It is not possible to do that without everything there, including the keys that you have.
 
I went through alternator after alternator in my gen I. Once I had a problem similar to the one that you are describing. I had 13.X volts with the car running and check charging system message on. I spent hours messing with things myself and had the car in my buddies shop. He thought that it was the PCM because the signal wave coming from it to the alternator (voltage regulator control) did not match what the Snap-on specs were saying. Long story short I got a Motorcraft reman to try (before buying PCM) and that solved my problem. I realize that you are probably looking at PCM now too, but maybe like joegr said the alternators were your initial problem.
 
Yeah I went through all those. It has a new OEM motorcraft alternator, a new battery installed. When I brought the car to the dealership, I drove it there. and when they tried to program the keys, it failed. I then brought them two other pcms that i had no clue if they came of a working LS. After all those pcm failed to work. Dealer couldn't find the problem why it fails. So I got a new pcm that I know came off a good working LS and matching serial number. Because I have a same LS for parts. When I was taking it apart I noticed the pcm was taken off before. For me was a worth a try. because the dealership couldnt program the keys to any of the pcms. The car stood there for weeks trying to find the problem. I know the original pcm worked because the car started. I didnt know that you had to have to same serial numbered pcm. I brought them a different serial number and they tried to program it. and Of course it failed. then I brought them my parts cars pcm, which that failed too.like i said before the bolts were stripped, a sign that the pcm was changed before I bought the parts car. Sorry for the long post.
 
A magical thing happened today. As I said my LS didnt start because of the dealership messing it up. I Have a new PCM installed and planning to take it to the dealer again for key programming. I never programed the new pcm. I was getting the car ready for tow and decided to try to crank it. Once I tried it, she started right up. I was shocked seeing it start because I didnt program the new pcm yet. So I check the voltage, even the new pcm is still putting out 13.3v. New alternator, battery, cleaned out all the negative and positive leads, threw in another ground wire, checked and traced wires and found nothing. Any other ideas any could give me??
I have gone through 3 motorcraft generators and on aftermarket, and still 13.3v.
 
Wow, that's not supposed to be possible.

As for the alternator, there are two lines to look at first. The control line from the PCM to the alternator and the feedback line from the alternator to the PCM. An oscilloscope may be needed to do any good here.
 
New update!! I hooked up a snap-on OBD-ll computer and found a code. P1246 - Alternator load input failed
Does this mean my new pcm is bad too? or the alternator plug is shorting out?
Does any one have the info on the voltage current that goes through those 3 wires on the alternator plug. Want to see what voltage will give me to the pcm and to the generator.
Thanks
 
The best thing to do first would be to trace the two wires that are between the alternator and the PCM. With both the PCM and the Alternator unplugged, you should read infinite resistance between each of the two wires and ground. Next, you should read less than 3 or 4 ohms from one end of each wire to the other end.
 
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