E40 stopped PWM fan control

A little help, please. Anyone ever run across a PCM that stopped outputting PWM fan control?

2005 LS2 (E40) suddenly stopped PWM (elec) fan control of aftermarket Spal brushless fan. Contacted Spal and confirmed it's not a bad fan by grounding white and powering yellow. PWM signal was being sent over white wire and never had yellow wire hooked up. While troubleshooting, loaded a discrete fan tune and was able to trigger fan wire to create a ground with scanner function... thought I might have knocked a wire loose. Any help is appreciated. Thanks

This is when it's really nice to have an oscilloscope. Without one you're left with not a whole lot other than just guessing and throwing parts at it.

Did you try commanding a fan % in the scanner special controls?

May be a dumb question but just making sure... Do you have a relay in line or are you trying to ground the fan directly off of the fan signal?

No relay with the variable speed brushless fans.

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Originally Posted by blindsquirrel

No relay with the variable speed brushless fans.

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Ahh I see. I saw "aftermarket" and assumed he was attempting to run a standard 12v fan. My mistake!