Advanced question about charging system Urgent!!

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scjmc

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I am having a charging system issue that I cannot resolve. I had an intermittant charging problem verified with a volt meter. I replaced the alternator and now the car charges (14.2V), however the "check charging system" message and bettery light are illuminated. I checked the circuit (red lead is battery voltage). The GY/RD lead is signal from PCM which the Snap-on meter shows a digital pulse every 11-21 seconds. The alternator output to PCM WH/something sends that pulse back. My question is what frequency should the pulses be? Snap-on says every 5 seconds, but another resource said that it should be on/off/on/off/on/off etc. My mechanis thinks the PCM is bad. He said that he can reflash the PCM with the newest software to try. Does anyone have any input? Please dont say take it to the dealer becasue my dealership is incompetent and I have a bad relationship with them. The next closest one is about 140 miles away. My mechanic is a personal friend and is very skilled. I worry about a PCM replacement because I fear that it may be unnecessary, and will render my tune from Torrie unusable. I am waiting back from him on that. Thanks for any help!!!!
 
Thanks for the replys. Torrie got back to me and he said that my tune should work with the new software revision. He really does offer good customer service because he got back to me in about 30 minutes even though it is the evening. I hope the new software works. I will be mad if I end up buying a PCM and that not solving the issue.
 
Getting the flash done today. I will let you guys know if it makes any differance.
 
A little late, but...

I would think that the PWM signal from the PCM to the alternator, and from the alternator to the PCM would be fairly high frequency (at least hundreds of pulses per second).

My understanding is that the PCM will command the battery light to be on if the PWM from the alternator goes to either 0% or 100%, anywhere in between and the light should be off. I think the same goes for the PWM to the alternator. With my scan tool, I can get a real time reading of the PWM percentage for both signals (as the PCM sees it), as well as the battery voltage that the PCM is reading.
 
I know ibis wierd. When monitoring both signals the PCM sends 2 square waves to the alternator every 11 or 21 seconds. Sometimes it is longer than that but usually 11 or 21. The alternator will duplicate the signal and send 2 square waves back to the PCM. The PCM also sends out a signal when the ignition is turned on. We verified continuity tithe PCM connector. Snap on says that the PCM should send a "digital signal" every five seconds. Another resource said that it should be 5 square waves, pause, 5 waves, pause etc. I am wondering if the alternator itself is causing the PCM to act strangely or is the PCM actually bad.
 
scjmc said:
I know ibis wierd. When monitoring both signals the PCM sends 2 square waves to the alternator every 11 or 21 seconds. Sometimes it is longer than that but usually 11 or 21. The alternator will duplicate the signal and send 2 square waves back to the PCM. The PCM also sends out a signal when the ignition is turned on. We verified continuity tithe PCM connector. Snap on says that the PCM should send a "digital signal" every five seconds. Another resource said that it should be 5 square waves, pause, 5 waves, pause etc. I am wondering if the alternator itself is causing the PCM to act strangely or is the PCM actually bad.
Click to expand...

I think that the odds favor it being the alternator, but I don't know.
 
reflash had no effect so I am going to try another alternator before replacing the PCM. My mechanic thinks that the PCM is bad but I am betting that the alternator is sending gibberish back to the PCM. Fingers crossed because another alt (warranty) is going to be easier than a PCM. It comes In Saturday so I will update on Monday if another alternator fixes the problem.
 
I picked up the car today. I was wrong the PCM flash did do something... Now the traction control light blinks constantly.
 
No, on or off it blinks fast like it does when I break traction. When I run through the status messages it even says advance trac OK. I removed the alternator and had the battery disconnected the entire time. When I reconnected the battery I turned the ignition on and it is still doing the same thing.
 
If you have advanceTrac and not just traction control, then it may need to be recalibrated. I'd ask that they do this at no charge since they probably messed it up in the first place with the PCM reflash.
 
Yes it is AdvanceTrac. What is the recalibration procedure? These are friends of mine and they will help me out if they have the required equipment. They have a good selection of electronic test sets, but probably not much propreitry ford stuff.
 
Solved!! I installed another alternator (dont buy anything but a Motorcraft alternator -thanks NAPA premium lifetime rebuilt). We cant figure out why the PCM was not outputting the proper digital signal before. I can only guess that the PCM did not like the alternator's return signal, so it did not put out normal language. I really hate changing the alternator in this car..... Now if I can only get the advancetrak light to stop blinking...
 
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