Gen3 PCM Fan Control
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Joined: Feb 2025
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From: Bismarck ND
Gen3 PCM Fan Control 5.3 4l60e B code out of the donor 2007 Silverado 1500 Classic, into a custom built off-road buggy.
Close to completion, the problem I am having is getting the pcm to control fan 1 and 2. I have searched numerous sites and blogs and have found all kinds of things, some conflicting as expected. What are the characteristics of the pcm signal before and after signalling for fan function and how would I use that signal. Since I have found some info that the A/C system may influence fan function I should add that I have deleted the A/C system entirely. Which makes me wonder if the pcm isn't receiving some signal that it should be getting from the A/C system that would let it know not to run the fan/fans for it's parameters. If I knew what I should see with fans off and fans on, it would point me in the direction of the solution. Thanks in advance for any ideas!
Close to completion, the problem I am having is getting the pcm to control fan 1 and 2. I have searched numerous sites and blogs and have found all kinds of things, some conflicting as expected. What are the characteristics of the pcm signal before and after signalling for fan function and how would I use that signal. Since I have found some info that the A/C system may influence fan function I should add that I have deleted the A/C system entirely. Which makes me wonder if the pcm isn't receiving some signal that it should be getting from the A/C system that would let it know not to run the fan/fans for it's parameters. If I knew what I should see with fans off and fans on, it would point me in the direction of the solution. Thanks in advance for any ideas!
07 NBS would have had dual fans from the factory so all of the fan settings should be in there and ready to go already and in factory form used a 3 wire pressure sensor to allow it to control fans off of refrigeration system operating PSI. It has a fan 1 and fan 2 output that grounds the relay coil which operates three relays in either parallel for high speed and series parallel for low speed
Without have AC has no impact on the fan operation it will strictly run off the engine temp tables and disregard and PSI settings in the fan controls.
If any of the fan relay control leads are not connected to fan relays it will cause the code you describe to set.
Without have AC has no impact on the fan operation it will strictly run off the engine temp tables and disregard and PSI settings in the fan controls.
If any of the fan relay control leads are not connected to fan relays it will cause the code you describe to set.
Last edited by 01WS6/tamu; Feb 11, 2025 at 05:15 PM.
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Also try logging or monitoring the engine coolant temperature. After my motor & PCM swap, the PCM was reading about 30F lower than the DIC, whereas they used to be within a couple degrees. A small adjustment to the sensor calibration fixed that, and now the fans work normally again.
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NNBS is the 07.5 up.
NBS 99-07 with 07 6 month run being classic body.
all NBS trucks 2005 up have stock electric fan setups.
Either way provided pcm is flashed to a 05 up truck it's got all correct settings for an electric dual fan setup as is. So if you wire up your fans using 3 relay setup like stock gm diagram the code will go away and you will have high and low speed as is running off of the ect only for fan speed adjustments.
If you check nelson, current performance etc they are vendors here and sell a cooling fan relay pack prebuilt land 12V land 2 pcm fan control wires, ground it and connect the fans then rock and roll.
NBS 99-07 with 07 6 month run being classic body.
all NBS trucks 2005 up have stock electric fan setups.
Either way provided pcm is flashed to a 05 up truck it's got all correct settings for an electric dual fan setup as is. So if you wire up your fans using 3 relay setup like stock gm diagram the code will go away and you will have high and low speed as is running off of the ect only for fan speed adjustments.
If you check nelson, current performance etc they are vendors here and sell a cooling fan relay pack prebuilt land 12V land 2 pcm fan control wires, ground it and connect the fans then rock and roll.
Last edited by 01WS6/tamu; Feb 12, 2025 at 02:31 PM.
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