PWM cooling fan(s) control using ECM

[andrewb70]

Originally Posted by PTAddict

Does anyone know what the difference between PWM electrical and PWM EV fan control signals in a GM ECU application? Is one +12V and the other a modulated ground? This latest CTS-V fan apparently is configured as PWM EV, and I'm trying to figure out how to emulate that with a Motec ECU ...

Thanks for any help.

Scott

Scott,

Have you tried using PWM- like we have done with the C6 fan controllers?

Andrew

[PTAddict]

Originally Posted by andrewb70

Scott,

Have you tried using PWM- like we have done with the C6 fan controllers?

Andrew

Andrew,

Thanks for responding. I think I should have explained my question better.

The fan is definitely PWM controlled. The question is, what is the nature of the modulated signal? For instance, you can pulse a +12V signal, or pulse a ground connection (some aftermarket ECUs control analog gauges this way, for instance). And some kinds of PWM control "invert" the logic, e.g. wider pulses can mean slower speed instead of faster.

The GM ECUs have 3 kinds of PWM configuration: PWM Electrical, PWM EV, and PWM MRF, as they are called in HPTuners. I'm quite sure that PWM Electrical is a modulated +12V signal, but I don't know what the others do, specifically the PWM EV signal for controlling the CTSV fan. Don't want to damage an ECU or fan controller by guessing wrong.

BTW, PWM EV is apparently so named because it's the signal type used to control the "electro-viscous" fan clutches on some trucks. I'm guessing by what I can Google that this could be a modulated ground, but I'm hoping someone with more GM ECU hands-on can clarify.

Thanks much,

Scott

[dontlifttoshift]

Doing a Connect and Cruise LSA. Is it confirmed that I can _not_ control the fans with PWM with a GMPP E67?

[andrewb70]

Originally Posted by dontlifttoshift

Doing a Connect and Cruise LSA. Is it confirmed that I can _not_ control the fans with PWM with a GMPP E67?

JP and I have discussed this quite a bit. When he was doing the white LS9 Camaro he had to do all kinds of BS to get it to work. He called GM and got some unclear information and was told PWM is not possible on the GMPP harness kits. This is in contrast to Scot's experience, but Scot's kit is much older.

I suspect at some point GM changed the firmware/OS (pure speculation) to render PWM not functional. JP ended up getting a used E67, refreshing it with a Corvette LS9 OS and was able to make it work.

Hopefully JP jumps in here to clarify, but that's my recollection.

Andrew

[dontlifttoshift]

Yeah, that's what I read, I was hoping that maybe it was just a Florida problem. Trying to make this install as OEM as possible and thought it would be a nice touch.

[andrewb70]

Originally Posted by dontlifttoshift

Yeah, that's what I read, I was hoping that maybe it was just a Florida problem. Trying to make this install as OEM as possible and thought it would be a nice touch.

Donny,

Presumably this is for a customer, in which case I would encourage you to make this work for him/her...It really makes for a much nicer driving experience. It may be a Florida problem, so you should try it out for yourself.

Andrew

[samckitt]

Scot's kit is much older? Scot me? What kit is older? My GMPP controller kit? How do I find how old it is?

Yes I'm running the fan through a PWM control box from a GMPP LS3 controller. Friend of mine is also. Had to add some wires to the harness, and reprogram ECM for it.

[mikels]

Originally Posted by andrewb70

JP and I have discussed this quite a bit. When he was doing the white LS9 Camaro he had to do all kinds of BS to get it to work. He called GM and got some unclear information and was told PWM is not possible on the GMPP harness kits. This is in contrast to Scot's experience, but Scot's kit is much older.

I suspect at some point GM changed the firmware/OS (pure speculation) to render PWM not functional. JP ended up getting a used E67, refreshing it with a Corvette LS9 OS and was able to make it work.

Hopefully JP jumps in here to clarify, but that's my recollection.

Andrew

While there has been several 'releases' of calibrations for the LS crate engines, the software has remained the same.

So enabling PWM fan control is matter of wiring properly and enabling in calibration.

Dave

[samckitt]

Somewhere in this thread is the pinout for the E67 with callout on which spots to add wires & pins to for the PWM functionality. I have the full pinout chart if anyone wants it. I also have a PDF with instructions on how to disassemble the ECM connectors.

[vannatta20]

Anyone have any luck getting PWM output from an E38 ecu with a camaro OS? No matter what settings I use it will not output a signal. If I use a truck OS I get a PWM signal easily. The truck OS does not see AC pressure. The car OS does. This is why I need to use a car OS. I used an oscilloscope to verify