alternator question

[Hart_Rod]

I'm getting the following DTC codes for the alternator:

[] P0621 - Generator L-Terminal Circuit (Pending) (History) (Current) (Immature)
[] P0622 - Generator F-Terminal Circuit (Old) (History) (Current) (Immature)


Ok, here's my setup: I have a speartech harness that has a 2 wires plug going into the alternator (red and grey). The alternator is a 2004 Silverado 145 amp alternator (internally regulated). Since it's internally regulated, can I turn these codes off? TIA

[BR3W CITY]

Take a look and see if the 1st plug wire is close to the alternator at all. It can actually cause fault codes if its too close. If your running a standard copper plug, you might wanna look at the generator voltage at idle, which you can change. Sometimes with copper plugs and aftermarket wires, they will draw more than the ecu wants to allow without thinking there is an electrical fault.

[Hart_Rod]

Originally Posted by BR3W CITY

Take a look and see if the 1st plug wire is close to the alternator at all. It can actually cause fault codes if its too close. If your running a standard copper plug, you might wanna look at the generator voltage at idle, which you can change. Sometimes with copper plugs and aftermarket wires, they will draw more than the ecu wants to allow without thinking there is an electrical fault.

No copper plugs, just standard NGK's. The alternator wire is a pretty good distance from the first plug. Doesn't the E38 try to regulate the voltage unless it's turned off in the tune?

[BR3W CITY]

I imagine it may, but I'm looking to see if there is another cause. I don't wanna turn off codes that may help show a REAL problem, just incase...since then we'd ignore the real issue if the code no longer would pop.

If its the inherent cause, then ya turning it off will "solve" it, though I don't think that code itself will cause any tuning or mechanical issues.

[Hart_Rod]

Originally Posted by BR3W CITY

I imagine it may, but I'm looking to see if there is another cause. I don't wanna turn off codes that may help show a REAL problem, just incase...since then we'd ignore the real issue if the code no longer would pop.

If its the inherent cause, then ya turning it off will "solve" it, though I don't think that code itself will cause any tuning or mechanical issues.

Thanks BR3W, I agree about not turning off codes unless it's certain, there is know real problem. Let me know what you figure out.

[dayj1]

Originally Posted by Hart_Rod

I'm getting the following DTC codes for the alternator:

[] P0621 - Generator L-Terminal Circuit (Pending) (History) (Current) (Immature)
[] P0622 - Generator F-Terminal Circuit (Old) (History) (Current) (Immature)


Ok, here's my setup: I have a speartech harness that has a 2 wires plug going into the alternator (red and grey). The alternator is a 2004 Silverado 145 amp alternator (internally regulated). Since it's internally regulated, can I turn these codes off? TIA

Aren't you using the e38 ECM? In the stock setups a GBCM (Generator Battery Control Module) is used to monitor current draw. The GBCM "talks" to the body controller which "talks" to the ECM over the CAN bus.

So, long story short, this setup doesn't work without the GBCM and BCM and you need to turn off the codes you asked about. That's assuming that your Speartech harness is wired to run the 2004 alternator with the internal regulator and not trying to control it with the ECM.

[Hart_Rod]

Originally Posted by dayj1

Aren't you using the e38 ECM? In the stock setups a GBCM (Generator Battery Control Module) is used to monitor current draw. The GBCM "talks" to the body controller which "talks" to the ECM over the CAN bus.

So, long story short, this setup doesn't work without the GBCM and BCM and you need to turn off the codes you asked about. That's assuming that your Speartech harness is wired to run the 2004 alternator with the internal regulator and not trying to control it with the ECM.

It is an E38 ECM. I had Speartech install the plug for the Silverado alternator. When you say wired to run the Silverado alternator, can you be more specific? I can go in the tune and turn off the, voltage control of the alternator. Here's a screen shot of HPTuners with the section I'm talking about.

[dayj1]

I'm going to use "2007-up alternator" in my example, but I'm referring to any alternator with a PWM (pulse width modulated) voltage regulator. The exact year that a particular platform went to a PWM voltage regulator depends on whether we're talking cars/trucks/vans/etc. To my knowledge, all Gen IV application originally came with this type regulator.

The 2007-up alternator is controlled via a PWM signal from the e38, but the control lines from the ECM to the alternator are ECM outputs. The input side of the equation is from the BCM/GBCM setup that I described above. Most swaps can't accomodate that since it's not "normal" to include the BCM in a swap.

So, there are two options:

1) Run the original 2007-up alternator wired to the ECM with the 2 factory control lines (exact pin numbers may vary by application but I can look up a specific year/model if you let me know what donor we're talking about). With this option, the alternator will default to 100% duty cycle (13.8 volts) and throw alternator DTCs. You'll need to disable the codes.

2) Run a 2004 style alternator. The e38 cannot control the type of regulator in this alternator directly, so you still need to turn off the DTCs for the alternator. The difference is in the wiring. The regulator on the alternator will have 4 pins; "P","L","I/F", and "S". You'll need to hook up two of the terminals: "L" needs to go to an idiot light or a 470-ohm 1/2 resistor. The other side of the light/resistor needs to go to a switched 12V supply (i.e. hot with the ignition on). The "S" terminal needs to go to 12V hot at all times.

Either method will work. The argument can be made that option 2 is better because the regulator is actually "regulating" and not defaulting to 100% duty cycle, but you have to buy a new alternator. I personally went with option 1 on the 2007 LY5 (e38 ECM) swap that I finished up last week.

[Hart_Rod]

Originally Posted by dayj1

I'm going to use "2007-up alternator" in my example, but I'm referring to any alternator with a PWM (pulse width modulated) voltage regulator. The exact year that a particular platform went to a PWM voltage regulator depends on whether we're talking cars/trucks/vans/etc. To my knowledge, all Gen IV application originally came with this type regulator.

The 2007-up alternator is controlled via a PWM signal from the e38, but the control lines from the ECM to the alternator are ECM outputs. The input side of the equation is from the BCM/GBCM setup that I described above. Most swaps can't accomodate that since it's not "normal" to include the BCM in a swap.

So, there are two options:

1) Run the original 2007-up alternator wired to the ECM with the 2 factory control lines (exact pin numbers may vary by application but I can look up a specific year/model if you let me know what donor we're talking about). With this option, the alternator will default to 100% duty cycle (13.8 volts) and throw alternator DTCs. You'll need to disable the codes.

2) Run a 2004 style alternator. The e38 cannot control the type of regulator in this alternator directly, so you still need to turn off the DTCs for the alternator. The difference is in the wiring. The regulator on the alternator will have 4 pins; "P","L","I/F", and "S". You'll need to hook up two of the terminals: "L" needs to go to an idiot light or a 470-ohm 1/2 resistor. The other side of the light/resistor needs to go to a switched 12V supply (i.e. hot with the ignition on). The "S" terminal needs to go to 12V hot at all times.

Either method will work. The argument can be made that option 2 is better because the regulator is actually "regulating" and not defaulting to 100% duty cycle, but you have to buy a new alternator. I personally went with option 1 on the 2007 LY5 (e38 ECM) swap that I finished up last week.

The main reason I went with the 2004 alternator is because I couldn't find a 2007 and up alternator that would fit the bracket setup that I have (5.5" bolt spacing). Do you know of one that will work? If not, I will have to rewire it like you have indicated.

Edit: How do I verify that my harness is wired one way or another? If I check the voltage key off, the L and F wires have 0 voltage. With the key on, L has 0 voltage and F has 12 volts....I also forgot to mention that I am not using a BCM.

[dayj1]

Originally Posted by Hart_Rod

The main reason I went with the 2004 alternator is because I couldn't find a 2007 and up alternator that would fit the bracket setup that I have (5.5" bolt spacing). Do you know of one that will work? If not, I will have to rewire it like you have indicated.

Edit: How do I verify that my harness is wired one way or another? If I check the voltage key off, the L and F wires have 0 voltage. With the key on, L has 0 voltage and F has 12 volts....I also forgot to mention that I am not using a BCM.

I just measured the bolt spacing on a 2001 Silverado alternator that I had laying around, and the bolt spacing was 5.5" just like the 2007 Silverado alternator on my LY5. So, a 2007 Silverado (new body style since 2007 was a crossover year) has a 5.5" bolt spacing. The 2007 alternator is a 145A unit with "DR44" cast into the front cover. However, I'd run the 2004 unit if it were mine.

You can verify how your wiring is set up by unplugging the ECM and the alternator and "ohm-ing" out the wires with a voltage meter. If the alternator wires run to the PCM, that won't work for a 2004 alternator. You'll need to run the wires from the 2004 alternator as I described above to get it to regulate correctly.

[dayj1]

Here's a good thread on the different types of Gen III alternators:

http://ls1tech.com/forums/conversion...aq-thread.html

Look at the diagram that says "2001-? trucks". It shows wiring the "L" terminal as I described, but they used the "F" terminal to 12V instead of the "S" terminal. You can easily try both. You can verify which one (or both) work for you by measuring battery voltage with the engine off and running. If the voltage goes up when you crank the engine, the alternator is charging. The method at ls1tech would be easier to try first since your pigtail sounds like it's already wired up for those two pins.

[BR3W CITY]

This poses the interesting question; if its wired for ecm regulation, but it already regulated at the alt, and you shutoff the ecm control for reg, then does it really need to be re-wired? (whereas I can see if you put an un-regulated alt on a gen III, you'd end up possibly frying things)

[Hart_Rod]

Originally Posted by dayj1

I just measured the bolt spacing on a 2001 Silverado alternator that I had laying around, and the bolt spacing was 5.5" just like the 2007 Silverado alternator on my LY5. So, a 2007 Silverado (new body style since 2007 was a crossover year) has a 5.5" bolt spacing. The 2007 alternator is a 145A unit with "DR44" cast into the front cover. However, I'd run the 2004 unit if it were mine.

You can verify how your wiring is set up by unplugging the ECM and the alternator and "ohm-ing" out the wires with a voltage meter. If the alternator wires run to the PCM, that won't work for a 2004 alternator. You'll need to run the wires from the 2004 alternator as I described above to get it to regulate correctly.

I'm waiting on speartech to answer me on the wiring. If I is setup to be regulated by the computer, I can use the 05 Silverado alternator, correct?. If not, it looks like I need to add a wire from the battery to the "S" terminal. By not having the after to the S terminal, what is not happening that should be? I had the alternator checked and was told that it is charging.

[dayj1]

Originally Posted by BR3W CITY

This poses the interesting question; if its wired for ecm regulation, but it already regulated at the alt, and you shutoff the ecm control for reg, then does it really need to be re-wired? (whereas I can see if you put an un-regulated alt on a gen III, you'd end up possibly frying things)

I can wire anything, but I don't tune. So, at the risk of misunderstanding how the tuning software works, I don't believe that you tune out the alternator control from the ECM. In other words, you can turn off the trouble codes that signal when something doesn't work, but the ECM is still attempting to control the regulator. So, I would feel uncomfortable with wiring in an idiot light, etc. and leaving the ECM alternator control wires in place.

[dayj1]

Originally Posted by Hart_Rod

I'm waiting on speartech to answer me on the wiring. If I is setup to be regulated by the computer, I can use the 05 Silverado alternator, correct?. If not, it looks like I need to add a wire from the battery to the "S" terminal. By not having the after to the S terminal, what is not happening that should be? I had the alternator checked and was told that it is charging.

The "S" terminal is the "sense" terminal as in voltage sense. It monitors the voltage level to know when to crank up the regulator to a higher charge rate. Depending on the particular regulator, sometimes it isn't needed as it basically senses from the "batt" terminal on the alternator through an internal jumper.

Sorry that I confused the issue by mentioning using the "S" terminal first, but I'd try wiring the 2004 alternator you already have like the diagram I linked from LS1 tech. Especially since it uses the wires that you already have in your alternator pigtail.

As for the 2005 alternator, I think it uses a GBCM like the E38 computers that showed up in 2007. I wouldn't spend the money on another alternator. I'm confident that the 2004 will work fine with just a wiring change.


EDIT: I checked the alldata diagrams for the 2005 Silverado and it definitely uses a GBCM. So a 2005 alternator is not the answer unless you have the GBCM and then I'm still not sure that the e38 will control it correctly since the GBCM setup is not the same between 2005 and 2007.

[Hart_Rod]

Here's a picture of my alternator setup:

[Hart_Rod]

Is this how the 2004 alternator should be wired?

[dayj1]

Originally Posted by Hart_Rod

Is this how the 2004 alternator should be wired?

The short answer is "no". I think you have the plug labelled backwards. If you unplug the harness from the alternator, the plug on the alternator is part of the actual voltage regulator. The housing of the plug should literally be marked "P" "L" "I/F" and "S" on the side that has the locking tang for the connector. It looks like the terminal that you labelled "S" is actually "P".

After you verify that they are labelled backwards, here is the function of each terminal.

"P" (pulse) is not used. It connects internally to the stator and provides a pulse signal that varies with alternator RPM.

"L" (lamp) is the charge indicator circuit. It goes to an idiot light or a resistor (470 Ohm 1/2 watt is a good value)

"I/F" (ignition/field) goes to 12V ignition (i.e. hot with key on)

"S" (sense) goes to B+ (hot at all times). You can run the wire to a remote location (like the main fuse box feed) to regulate charging based on the voltage drop that occurs through the wiring, but the regulator will use the internal sense circuit if you leave it disconnected. If you're just going to run a wire down to the battery post, you may a well just let the internal sense do it's thing because there is effectively no voltage drop at the alternator BATT terminal.

Here's what I suspect is going on with the way that you have it wired right now:

It charges, but the e38 isn't getting feedback from the GBCM and is throwing codes. The e38 is defaulting the duty cycle of the alternator to 100% (13.8 V). This isn't necessarily bad, but the regulator really isn't regulating. It just maintains 13.8 V regardless of the total system current draw.

If it were mine, I would wire it as follows:

Take the wire from the "L" terminal and route it to an idiot light (if you have one or a 470 Ohm 1/2 resistor if you don't). The other side of the bulb/resistor should go to a switched 12V source (i.e. hot with the ignition on)

Take the wire from the "I/F" terminal and run it directly to a switched 12V source.

Forget the "S" wire (that you don't have) for now.

In order to run the two wires, you'll probably have to depin them from the ECM connector although it is possible that they are already connected this way inside the harness. You'll just have to look at the harness and possibly ohm them out with a meter to verify.

EDIT: Just for clarification, the short version of what I'm trying to get across is that the e38 controls the alternator based on GBCM input. Without a GBCM and BCM, the alternator is never going to work as GM intended (although it will work at 100% duty cycle).

By wiring it as I outlined above, it will regulate the voltage depending on load completely outside of ECM control. Then you just turn off the DTCs in the ECM and use your voltage gauge/idiot light to monitor the alternator's function.

[Hart_Rod]

OOpppsss! DayJ, I had my label backwards. I think it's wired like you said. I'm just waiting on verification from John at Speartech. Now I just need to figure out these 2 codes, .

[] P057C - (SES) (Pending) (Old) (History) (Current) (Immature)

[] P2537 - Ignition Switch Accessory Position Circuit Low (Old) (History) (Current) (Immature)

Thanks for all of your help!!

[Daaaanz67]

Great info dayj1 you have a pm

[dayj1]

Originally Posted by Hart_Rod

Now I just need to figure out these 2 codes, .

[] P057C - (SES) (Pending) (Old) (History) (Current) (Immature)

[] P2537 - Ignition Switch Accessory Position Circuit Low (Old) (History) (Current) (Immature)

Your motor is from a 2013 Camaro, right? If so P057C is "Brake pedal position sensor low voltage". When I looked at the schematics for you on how to hook up your brake signal switch in another thread I remember seeing that the new Camaros have a sensor to measure the amount of brake pedal travel. Since you wouldn't use that in a swap vehicle, I would think it's OK to disable that DTC if you can.

Unfortunately, P2537 doesn't even show up in the reference material that I have.

Here's a description of the brake pedal circuit from GM:

DTC P057C
Brake Pedal Position Sensor Circuit Low Voltage

Circuit/System Description

The brake pedal position (BPP) sensor is part of the engine brake pedal override feature. The engine control module (ECM) continuously monitors the vehicle speed and the position of the brake pedal. These two main inputs, along with other ECM inputs are used to determine if the vehicle is decelerating at the proper speed and rate with the brake pedal applied. When the engine brake pedal override system is active, the ECM reduces engine torque to assist in reducing vehicle speed.

The BPP sensor is a three wire sensor, connected to a 5 V reference circuit, a low reference circuit, and a signal circuit. The ECM supplies 5 V to the BPP sensor, and also provides a sensor ground path on the low reference circuit. The BPP sensor sends a voltage signal to the ECM on the signal circuit. The voltage on the signal circuit will vary from a voltage greater than 0.25 V when the brake pedal is released to a voltage less than 4.75 V when the brake pedal is fully applied.

I found this part interesting as well. I think you would probably notice the underlined part

Action Taken When the DTC Sets

DTCs P057B, P057C and P057D are type A DTCs.
Engine torque is reduced to 50 percent of available engine torque.
Brake torque management is active at 25 kpa (3.7 PSI) of brake pedal apply press

[Hart_Rod]

Great info DayJ! John from Speartech confirmed that my harness was wired like the truck one above (including the resistor for the lamp light). I turned off those 2 codes. It's really weird that the P2537 code pops up. It's not even listed in the DTC of HPTuners.... As far as the 057C code, makes me wonder if I should just turn the Brake Torque Management off in the tune? Here's a pic. Thanks as always!

[dayj1]

Originally Posted by Hart_Rod

Great info DayJ! John from Speartech confirmed that my harness was wired like the truck one above (including the resistor for the lamp light). I turned off those 2 codes. It's really weird that the P2537 code pops up. It's not even listed in the DTC of HPTuners.... As far as the 057C code, makes me wonder if I should just turn the Brake Torque Management off in the tune? Here's a pic. Thanks as always!

That's good news on the alternator wiring. No changes needed other than turning off the codes.

I finally found P2537. Check the transmission connector, pin 9. It was dark blue in the factory harness and is supposed to be 12V when the ignition is on. The code is tripped whenever the TCM doesn't see the voltage for over a minute.

[BR3W CITY]

Originally Posted by dayj1

I can wire anything, but I don't tune. So, at the risk of misunderstanding how the tuning software works, I don't believe that you tune out the alternator control from the ECM. In other words, you can turn off the trouble codes that signal when something doesn't work, but the ECM is still attempting to control the regulator. So, I would feel uncomfortable with wiring in an idiot light, etc. and leaving the ECM alternator control wires in place.

Well, you can change the desired voltage output that the computer is shooting for. If that value can be set to a value below anything it would ever recieve (so 0 or a negative), I would think its possible to "satisfy" the ecm, which when then prevent the code from turning on at all. I don't think those codes will trigger a limp mode or pull timing or anything like that, so the effect wouldn't be negative.

I never had to address the issue myself, so I can't say for sure how the computer would react to setting the value that low. It can always be changed back, so there really isn't a risk in trying before making hardware changes.

[Hart_Rod]

Originally Posted by dayj1

That's good news on the alternator wiring. No changes needed other than turning off the codes.

I finally found P2537. Check the transmission connector, pin 9. It was dark blue in the factory harness and is supposed to be 12V when the ignition is on. The code is tripped whenever the TCM doesn't see the voltage for over a minute.

Turning off the 3 codes seems to have eliminated the "phantom code", .

Originally Posted by BR3W CITY

Well, you can change the desired voltage output that the computer is shooting for. If that value can be set to a value below anything it would ever recieve (so 0 or a negative), I would think its possible to "satisfy" the ecm, which when then prevent the code from turning on at all. I don't think those codes will trigger a limp mode or pull timing or anything like that, so the effect wouldn't be negative.

I never had to address the issue myself, so I can't say for sure how the computer would react to setting the value that low. It can always be changed back, so there really isn't a risk in trying before making hardware changes.

I'm not sure about the Gen3s, but the Gen IV's will let you prevent the ECM from controlling the alternator. At least that's what I think this screen is for. Check it out: