Yes. I got the new battery in yesterday and the alt. Is still out now... Looking for one i can use. Best price so far is 45. W/ core.... Why would i not replace them??? The are bad... No worries. My regulator is going out. Read the diag hand held myself... And yes. It will prove a point.


Thanks for the "terminology"... What does each one do specifically????

 

In a single module setup, the PCM handles the entire EFI system whereas, in a dual module setup, the ECM is specifically programmed to electrically handle the fuel system and a lot of other things such as sensor inputs and outputs that otherwise, would normally be handled by the PCM.

In this config, the PCM does NOT control certain functions and, in this mode, the ECM is the main controller for the EFI system. The bulk of bussed messages are stored in RAM at the EMC level and not at the PCM level.

In this type of setup, the PCM’s main function is to control: the vehicle charging system, speed control system, transmission, air conditioning system and certain bussed messages.

So, the rectification CKT, the regulator CKT, etc, still reside at the PCM level while all the other tasks for fuel systems are done at the ECM. Hope that helps clear this up for you.

CM

 

WOW!!! i have a secondary code not setting off a fault code... For the CKT selenoid low or high voltage... Everythign is pointing to the PCM but also I thinks the regulator is just bad bc it affects all the problems ive listed in this thread.... Is the PCM the one on the passenger side fire wall?? Or is that the ECM as I thought???? Also if that is the ECM where is the PCM???

 

Please forgive me for asking but, would it be possible to list out your issues? If you would, list out the problems. I didn't go through this entire post and, I apologize for that but, I was hoping that you could list out the issues like seen here:


SYMPTOMS and ISSUES

-issue 1

-issue 2

Along with what was done as seen here:

What was done:

- performed electrical testing

- ran diagnostic scan tool and codes were P0XXX, P1XXX etc etc

- Performed OHM test on X-wire etc.

In addition to that, if there's anything that has happened, such as a huge arc when connecting power, removing or attaching a harness, battery terminals, ALT ground, case ground whatever, please post that information so I can help you determine possible failure mode/s.

This will help me to determine where your problem is rooted and, to what systems may be involved.

Regards,

C. McKenna

 

And yes, the PCM is the one on the firewall.

 

Ok. Thats what I thought it was...

Well bought the alternator today... Slapped it in and same thing. 11.87 volts to the battery... regulator has been verified bad 4 times now... Can the regulator be what is making it want to die or stall out??? After I put the new alternator on the roughness in the idle seem to disappear but can still kinda feel it in the pedal... I found a PCM for $50. and will get when I have the money.... I am doing the regulator bypass first thing in the a.m..... For I did not have time today. Both alternators passed 4 different bench testes. So how can they only be putting out 11.87 volts to the battery??? Doesnt make sense....... The only two things I can think is a simple connection issuse which I mave have overlooked or just that the bad voltage regulator is causing this problem...

Original problem was a rough idle and truck wanting to stall at braking or turning...

Battery been replaced

Alternator been replaced but gonna keep the old one bc it tested good.

All connections of my knowledge have been verified tight and clean.

Breaking out the digital current tester in the a.m. as well and see if it may be a short in the middle of the wire somewhere....


If anyone has another thought to what could be causing this issue please let me know.... Theres only so many thing it can be in the charging system....

 

The alternator testing good really throws me for a loop bc last night after i bought my new battery I drove for maybe 15 mins and the new battery was completely zapped!!! 0 charge when they tested it.... Just doenst make any sense how the alt can be good yet fry a battery so quickly....

 

Actually, this is a very simple system and, let me walk you through each component in this system.

-source, this is the battery and, a good battery under no load condition will measure ~12 volts. Place the meter across the battery, and set it in the window. Turn the key to <START> and note voltage drop- should be ~ 9 volts when you hit the starter on a healthy battery. If it dives below that, there's a dying / dead cell connector. Remove and replace battery.

-ALT: this supplies the 14 volts to charge the battery. The rectification and regulator are at the PCM level thus, if your regulator is not putting out full power it could be a fault in the rectifier stage and not the regulator or, as stated, it could be a faulty driver CKT at the regulator stage. Either case, the PCM must be replaced. However, there's a few other things that will induce this same symptom and that is, a high resistance ground or, on the POS (+) side.

In order to test this, simply run an OHM test on the grounds and hots. Of course, remove the battery from the CKT to prevent dead shorting to ground and damage to the meter.

You may also see / find a high resistance at the fuse level / PDC level thus dropping voltage there. Pull the fuses and ohm them out, check contacts for corrosion. Check all frame grounds and, I would remove them all one at a time and OHM them out to rule them out as suspect.

All the grounds at the frame, the ALT top bracket, starter motor, etc, check all connections for, corrosion in the winter can set in and cause a voltage drop large enough to throw the entire electrical system out of whack thus creating erratic behavior.

The system is designed to run on ~14 volts and, there's a ± X-amount of volts that it will still run on fine and, in similar systems such as automotive applications, this is normally around 2 volts. Anything that falls out of this range- the electronics will never work as intended.

For example, if the supply voltage falls below the lower limit, the voltages inside the PCM also drop. Without going to deep into this here, this lower voltage throws the entire scaling relationships of all CKTS out of balance thus, all your sensors will be out of whack, the readings at the PCM inputs will be off, as well as the outputs. Nothing will work correctly is what I am trying to say here.

Now, for sure, the regulator as well as the rectifier CKTS may be faulting. However, you, the end user, can not test this nor know with absolute certainty that this is the case here without electrically testing the PCM input to output relationship on those CKTS.

However, what you can do is check outside the box. You'd simply start with the battery and measure across the terms. Place the meter in the window and, you'll see roughly 12 volts.

Place a load on the battery such as turning on the headlamps- note voltage.

Hit the starter-note voltage drop. If it drops <3 volts- good , if drop is > 3 volts, you've got an issue with the battery- dying / dead cell connector.

After verifying the battery / source, your going to work your way out from there one wire at at time. NOTE: REMOVE BOTH BATTERY leads before testing.

Measure each wire for resistance.

Measure each fuse for resistance.

Measure the ASD relay for resistance in both powered and NON-powered mode. Here's a great source of dropping voltage like mad due to high contact resistance. OHM that to OEM specs. Get a manual as it describes how to do it step by step or, you can search for my posts on here as I have listed this out a few times.

There's a POS (+) that runs from the ALT to the PDC- trace it out and OHM it out.

From there, your going to find another wire of the same color code GR/OR that feeds into the PCM- remove the connector, trace it out, OHM it out.

Trace out the main feed to the starter motor, you may want to remove the starter and check for high contact resistance as well as the ground while your at it.

There's your PLUS side of the charging system with the starter thrown in. If there's a partial short in the starter motor windings, it will drop voltage to ground. This is another possible failure mode- partial short in the windings of the motor. You can test that by OHM testing that as well to OEM specs.

Now, for the MINUS (-) side, your going to start at the source and work outward in the very same manner- one wire at a time. OHM them out. The ALT isolated ground- OHM it out and, same goes for the main engine ground at the ALT stud.

Your just going to have to check those main wires and that's about it - along with the battery / source and your starter motor and, the PDC.

I have schematics so, if you need more information, we can go into depth but, what I have listed should keep you busy until we get to that point.

Once you've verified to that level that all checks out, then, at that point, it's most likely a fault at the PCM level.

CM

Check your frame grounds from the battery.

 

I have the answer for that: The ALT is only HALF the CKT. The remaining half resides at the PCM level therefore, if, the rectifier stage is blown, you've got nothing- no voltage- dead.

It will run off the battery and, since the PCM will NOT run off the battery current, lower voltage, you get erratic behavior.

Now, another thing comes to mind when I read that it was at zero volts. If that was a good battery, and it dropped to zero volts- there's a good chance that there's a partial short to ground.

This would also explain the voltage drop at the battery input or, it was merely not there to begin with thus the reading you obtained before was merely the battery output and not the ALT output at all.

So, the real question is:

Is it dropping voltage due to a short condition or, is the rectification stage totally shot- that's what you need to determine.

CM

 

Both alternators were passed on all three stages on 4 bench tests.... The output reading from the ALT, which was 11.87, was acquired with a hand help device to the battery after start up.... I kinda thought it would be a ground... but I thought more that it was the PCM... I knw the regulatro is out for sure. Same hand held test showed that. Y i was gna do the internal voltage regulator bypass in the a.m...

What is CKT??
What does it funtion???
bc i have a fault code for ckt selenoid.....
w.e. that is....