HELP!! Please

[TooTall]

New Generator - Still Problems!!

11/4/04

Hope someone can lead me in the right direction here.

Replaced the Alternator about 30 days ago when I was having problems with charging. Three times over the last 30 days for no apparent reason I get a "Charge System Fault" on the DIC with codes of:

P1637 H Generator L-Terminal Fault

P1637 H C Generator F-Terminal Fault
With a drop in voltage as if no supply coming from the alternator.
This is intermittent as again for no apparent reason the problem then resolves itself.



11/5/04

OK, It is a remanufactured from Duralast (AutoZone). Went in this morning and they traded out for a new unit that tested good on the Duralast tester. Got it on and still no voltage from the alternator. Still haven’t checked any wiring except both engine grounds, battery leads and a visual check of the alternator wiring.

I understand that the voltage from the alternator is controlled by the PCM. Could it be that I have a faulty PCM?

I'm at a loss as to what to do now.

I have removed and cleaned both engine compartment grounds. I'm a diy kinda owner, but I don't know where to go next.

 

[KANE]

"Charge System Fault" on the DIC with codes of:

P1637 H Generator L-Terminal Fault

P1637 H C Generator F-Terminal Fault
With a drop in voltage as if no supply coming from the alternator.
This is intermittent as again for no apparent reason the problem then resolves itself.


OK, It is a remanufactured from Duralast (AutoZone).

I have removed and cleaned both engine compartment grounds. I'm a diy kinda owner, but I don't know where to go next.

Hey-

I have played with retro-fit TPI engines and have begun the C5 debunking myself.

I would check a couple of things, first of which being the BATTERY GROUNDS. Get this- GM HAD PROBLEMS WITH THE BATTERY TERMINALS FALLING OFF!! I know because mine did that. Well, more importantly your car is in questsion and you may have the same issues. There was a manufacturing problem and until the terminal actually falls off, you can't be sure if that isn't it!!! Remember- there are three ingredients to a charging system- BATTERY, STARTER, ALTERNATOR. Even in a system where a CPU controls the regulator, if one of the other three fails..... then you may have a problem that would imply one of the other members is at fault- but the reality is you still need to check all three to make sure!!! For you, that meands you need to check the battery.

c4c5specialist maybe able to give you some jedi knight info, but what I stated above would be a good guess.

 

[TooTall]

Took loaner alternator and my purchaced alternator back to AutoZone for check on the computerized machine (spins the alterator up and gives a pass fail indication). It shows as being good so they won't take it back. The battery is a 6 month old Optima Red Top and I have checked the terminals for any signs of weakness. Short of the Dealer (bad experiences) I'm at a loss on where to go from here.

 

[c4c5specialist]

New Generator - Still Problems!!


11/4/04

Hope someone can lead me in the right direction here.

Replaced the Alternator about 30 days ago when I was having problems with charging. Three times over the last 30 days for no apparent reason I get a "Charge System Fault" on the DIC with codes of:

P1637 H Generator L-Terminal Fault

P1637 H C Generator F-Terminal Fault
With a drop in voltage as if no supply coming from the alternator.
This is intermittent as again for no apparent reason the problem then resolves itself.



11/5/04

OK, It is a remanufactured from Duralast (AutoZone). Went in this morning and they traded out for a new unit that tested good on the Duralast tester. Got it on and still no voltage from the alternator. Still haven’t checked any wiring except both engine grounds, battery leads and a visual check of the alternator wiring.

I understand that the voltage from the alternator is controlled by the PCM. Could it be that I have a faulty PCM?

I'm at a loss as to what to do now.

I have removed and cleaned both engine compartment grounds. I'm a diy kinda owner, but I don't know where to go next.

Hi there,
First, lets look at basics.

The P1637 is for terminal L, not terminal F. Now, the PCM looks for certain things when you turn the key on.

When you turn the key on, the PCM sends a small voltage supply TO the alternator. This will NOT be battery voltage, it will be a small amount. As the voltage and current flow through the circuit, the PCM reads this as normal. Once the alternator starts rotating, the solid state circuitry of the alternator OPENS this circuit on terminal L so that NO electricity flows. The PCM sees this as normal and passes the DTC.

So now, in theory, our diagnostic trouble chart is ASSUMING that the alternator is operating correctly. I have a tough time believing that a Duralast will work correctly. Nothing but problems with these in CT. And the test that they are running are obviously only for voltage generation, nothing more. They dont even know what the PCM needs to see, just ask them.

So now, we come to this. Your tests will consist of the following to determine if this alternator is working correctly, OR the PCM is not working correctly.

Your alternator connector consists of 4 terminals, B terminal is a red wire. This is your "L" and is CKT225.
You will turn the ignition to the on position, do NOT start the car. Once this is done, disconnect the 4 pin connector from the alternator. First, take a look inside the connector, to make sure that the terminals are not spread open, creating an intermittant contact. If it is ok, proceed using a voltage meter connected to ground, obtain the actual voltage reading coming from pin B at the wiring connector, NOT at the alternator itself.

What do you have???????

Next, in order to test the alternator, turn the ignition OFF.
Now, put your electrical meter to OHMS. Test for resistance from terminal B at the back of the alternator to ground.

What do you have?????

My theory, and it is only that, is the follwing.

A) A bad alternator regulator, creating either no ground or incorrect voltage switching, which the PCM reads as a terminal "L" failure.

B) Wiring or terminal tension problems creating a voltage flow problem between the PCM and the alternator.

C) A bad PCM.

Let us know what you have, c4c5

 

[ErnieN85]

I agree probably the alternator the test they use doesen't check for the proper operation. (no computer control) I had one and the only way I got it to work was to buy a new AC Delco!

 

[TooTall]

C4c5

C4C5,

I was hoping you would respond to this thread. You always seem to have a solution or the right way of going about finding one. My next step will be to purchase the service manual, but right now I do not know where to find the pin B you refer to?

The only markings on the 4 pin connector on the alternator are "S F L" representing the three pins closest to the engine and no markings on the connector. The forth pin is not wired on the connector. On the connector the pin closest to the engine has a red wire, the next is a grey wire and the third is a red wire.

Could you give me a heads up on which is pin B?

Thanks for your help,
Rob

 

[TooTall]

Hi there,
First, lets look at basics.

The P1637 is for terminal L, not terminal F. Now, the PCM looks for certain things when you turn the key on.

When you turn the key on, the PCM sends a small voltage supply TO the alternator. This will NOT be battery voltage, it will be a small amount. As the voltage and current flow through the circuit, the PCM reads this as normal. Once the alternator starts rotating, the solid state circuitry of the alternator OPENS this circuit on terminal L so that NO electricity flows. The PCM sees this as normal and passes the DTC.

So now, in theory, our diagnostic trouble chart is ASSUMING that the alternator is operating correctly. I have a tough time believing that a Duralast will work correctly. Nothing but problems with these in CT. And the test that they are running are obviously only for voltage generation, nothing more. They dont even know what the PCM needs to see, just ask them.

So now, we come to this. Your tests will consist of the following to determine if this alternator is working correctly, OR the PCM is not working correctly.

Your alternator connector consists of 4 terminals, B terminal is a red wire. This is your "L" and is CKT225.
You will turn the ignition to the on position, do NOT start the car. Once this is done, disconnect the 4 pin connector from the alternator. First, take a look inside the connector, to make sure that the terminals are not spread open, creating an intermittant contact. If it is ok, proceed using a voltage meter connected to ground, obtain the actual voltage reading coming from pin B at the wiring connector, NOT at the alternator itself.

What do you have???????

Next, in order to test the alternator, turn the ignition OFF.
Now, put your electrical meter to OHMS. Test for resistance from terminal B at the back of the alternator to ground.

What do you have?????

My theory, and it is only that, is the follwing.

A) A bad alternator regulator, creating either no ground or incorrect voltage switching, which the PCM reads as a terminal "L" failure.

B) Wiring or terminal tension problems creating a voltage flow problem between the PCM and the alternator.

C) A bad PCM.

Let us know what you have, c4c5

OK Just experimenting with the two red wires I found the connector furthest away from the engine has voltage of 10.66.

The OHMS register 4.03 @ the 20K setting.

Checked the battery voltage also it is setting at 12.6

What does this mean?

 

[Silver97]

So what solved the problem??? It looks like I may be experiencing the same problem

 

[TooTall]

Well after many mornings of dead battery and hair pulling frustation, I finally gave up and went into the dealer.

Thier solution: "Electrical starter problem cause fusible link to fail - no current to alternator",
the fix: New starter and fusible link assembly.
Now keep in mind that the car would always start with a charged battery.

I had this done on the 10th of Dec and replaced the 6 month old Red Top with a new on the next day.
I run my DIC on battery current setting to keep an eye on it, and so far it is always in the high 12's low 14's. So I'm keeping my fingers crossed that that was actually the issue.

 

[Silver97]

Thanks alot for the quick responce...I will check the cables going to the starter and if all fails then take it to the dealer..