PWM cooling fan(s) control using ECM

[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