Make Newer CTS-V Alternator Work

[Shoeless]

Hey guys,

This was a fun one for me, but I somehow ended up getting the new Cadillac CTS-V Alternator even after taking copious notes a long while back telling me to get the older one. For anyone that was interested or read all the posts from a long while back, the newer one requires a PWM (Pulse Width Modulated) 5V signal operating at a variable duty cycle depending how much charge you want (67% cycle = 14 Volts), and at a set frequency. The older one simply requires a +12V switched signal.

So now I'm stuck with two options:
1. Sell it and buy the older style as I'm way out of the return period.
2. Find out a way to get my standalone ECU to crank out this signal.

I'm opting for option #2 before I go spend more money. I did tons of searching (Other forums and AEM Infinity FB Page) and a bunch of reading (400+ page ECU manual and supplemental documentation) and have found a solution with some input from others. So the AEM Infinity has two types of switching it controls (low side - switches to ground and high side - switches to 12V), but I need a 5V signal to start with. Thankfully there's a standard 5V power supply signal typically used for some sensor that I can use.

So now I have a 5V signal and a low side switch to bring the signal back to ground, but need an additional component, that's where a pull up resistor comes in. Here's what the circuit will look like



So this will now put a 0.05mA load on the 5V circuit (well within acceptable limits) and the lowside switch gets me to ground. Within the AEM software, I can set up a 2D table with duty cycle anywhere from 0-100 (Typical OFF and ON state) and frequency. I can even change the duty cycle based on engine RPM and have the alternator give more charge at lower RPM and less at Higher RPM.

Problem solved

[Jkviper]

This may help...

https://ls1tech.com/forums/conversio...hrow-away.html

[Shoeless]

This may help...

https://ls1tech.com/forums/conversio...hrow-away.html

That’s a pretty good write up too, I’ll have to double check the values he came up with against the table I have, probably very similar. Although, I didn’t like the idea of adding a PWM generator if I could figure out how to get my ECU to do it for me. Plus with the 2D tables I can set, I have all the control really needed to adjust voltage based on RPM.

Thanks for sharing it.

[Jkviper]

Your welcome. If you come up with another approach, please post. I also have a PWM alternator and have not gotten to the point of needing to figure it out yet.

[Shoeless]

Your welcome. If you come up with another approach, please post. I also have a PWM alternator and have not gotten to the point of needing to figure it out yet.

What kind of engine computer are you running?

[Jkviper]

What kind of engine computer are you running?

I have a Gen V LT4, planning on using a Stock ECU with a speartech stand-alone harness. I am assuming the stock ECU will handle the PWM for the alternator, but this is my first build so do not know for sure.

Going with a custom speartech harness since I am looking to hookup all the emissions equipment and the GM aftermarket ECU leaves some of those items out of the programming and harness.

[Ajzride]

I'm not sure if it would be any easier, but an Arduino Uno is under 10 bucks, and it has 5V PWM outputs. You could easily use one to read the RPMs and Voltage and generate your PWM curve.

[Shoeless]

I'm not sure if it would be any easier, but an Arduino Uno is under 10 bucks, and it has 5V PWM outputs. You could easily use one to read the RPMs and Voltage and generate your PWM curve.

Hey Ajzride,

My goal was to really figure out how to control the alternator with the Aftermarket Standalone ECU I already have without adding any other components. But you are correct, you can get an Arduino to kick out this signal and program it to adjust based on inputs of RPM and Voltage.

[beeman]

I hope I bought the right CTS-V alternator...

[Shoeless]

I hope I bought the right CTS-V alternator...

What's the part number on yours? Funny enough though, I think you bought the right one if you planned for 12V turn on. I saw your comments on post from years ago when the CTS-V Alternator option was mulling around the other forums.

25766345 is the Older PN and should be 12V turn on. 2006-2007 CTS-V
25925447 is the Newer PN and will be PWM turn on. 2009-2015 CTS-V