PWM cooling fan(s) control using ECM

[mikentosh]

Wondering if anybody has troubleshooting advice for the PWM signal coming from an E38 ECU? I'm not seeing any PWM signal coming out from X1 pin 58.

I took my multimeter and put black probe to DkGrn wire coming from X1 pin 58, and red probe to battery positive terminal, and set to DC volts. Turning key on I can see the voltage go up to about 1.2V but regardless of toggling fans and duty cycle in HP Tuners I don't see any change. I would expect to see either ~5V or ~12V across here but do not. I didn't even bother to switch my multimeter over to duty cycle measurement, but assumed without the higher voltage its not working.

Any ideas on further troubleshooting? Pin 58 is a ground PWM signal correct?

[andrewb70]

Originally Posted by mikentosh

....

...Pin 58 is a ground PWM signal correct?

That part I know to be correct, but I can't help with anything else.

Andrew

[mikentosh]

Originally Posted by andrewb70

That part I know to be correct, but I can't help with anything else.

Andrew

Thanks. I looked at it again on the weekend and realized that I was monitoring it while it was hooked up to the C6 fan relay. Once I disconnected the fan module I see it taking 12V to ground when key is on, regardless of fan state in the ECU. Interestingly I also flashed the ECU back to discrete fans and am observing the same situation, so I'm going to give up for now and wait until I've switched over to the Holley Dominator setup.

[andrewb70]

Originally Posted by mikentosh

...so I'm going to give up for now and wait until I've switched over to the Holley Dominator setup.

Now that, I can help you with!

Andrew

[mikentosh]

Originally Posted by andrewb70

Now that, I can help you with!

Andrew

Just as a followup, we did the switch to the Dominator setup and, as expected, its working great!

[andrewb70]

Originally Posted by mikentosh

Just as a followup, we did the switch to the Dominator setup and, as expected, its working great!

Excellent. The set-up on either the Dominator or the HP is pretty straightforward.

Andrew

[mikels]

Originally Posted by mikentosh

Wondering if anybody has troubleshooting advice for the PWM signal coming from an E38 ECU? I'm not seeing any PWM signal coming out from X1 pin 58.

I took my multimeter and put black probe to DkGrn wire coming from X1 pin 58, and red probe to battery positive terminal, and set to DC volts. Turning key on I can see the voltage go up to about 1.2V but regardless of toggling fans and duty cycle in HP Tuners I don't see any change. I would expect to see either ~5V or ~12V across here but do not. I didn't even bother to switch my multimeter over to duty cycle measurement, but assumed without the higher voltage its not working.

Any ideas on further troubleshooting? Pin 58 is a ground PWM signal correct?

PWM fan output is frequency output - will not be able to 'measure' with voltmeter.

Cal also needs to be set to PWM output and frequency matched to PWM controller. All E40, E38, E67, E92 (and most all other GM ECM's from recent years) are capable of PWM fan control.

BTW - GM crate controller wiring joins fan1 and fan2 outputs to relay - need to separate to send fan1 only to PWM controller.

Dave

[AJG87]

Originally Posted by mikels

BTW - GM crate controller wiring joins fan1 and fan2 outputs to relay - need to separate to send fan1 only to PWM controller.

Dave

As a follow up to this statement, on my GMPP E67 kit, schematic says C3-49 being a green wire to fuse bus position 7D. Is someone familiar enough to detail what the process here is, with regards to splitting fan1 and fan2, to make appropriate input connection at PWM controller @ position 6?

Thank you in advance!

Andrew

[dontlifttoshift]

GMPP harnesses only.

I have tried separating them and have been unsuccessful at getting two separate fan controls. You can operate two separate relays, with two separate fans but they will turn on and off at the same time.

......and once they come on, will not shut off until a set speed is reached, regardless of temperature.

[andrewb70]

Originally Posted by dontlifttoshift

GMPP harnesses only.

I have tried separating them and have been unsuccessful at getting two separate fan controls. You can operate two separate relays, with two separate fans but they will turn on and off at the same time.

......and once they come on, will not shut off until a set speed is reached, regardless of temperature.

This seems like more evidence to the fact that at some point GM changed the ECU in their kits.

The GMPP harness and ECU in my GTO were purchased in 2008. I don't have a speed input to the ECU. My fans turn on around 210 and turn off around 205.

Andrew