squared

I wired up a couple of cooling fans for my engineering prototype (boat) using the Camaro wiring diagram on a 411 PCM running a 2001 Silverado software load. Using HP Tuners, I configured the tune for it, using posts I've seen here and on the net as a guide. For wiring, I ran the PCM pin into a std. GM fan type relay with direct battery + on the other side. Fans are wired into the switched side of the relay with a 15A fuse on the Battery side.


The fans seem to work as advertised, but are pulsing on/off at a high rate and seem to run at about 50-70% normal speed. When I activate FAN1 in the Scanner, the fans speed up to full speed...not entirely abnormal(?). However, when I clear my Long Term Fuel Trim, I get the same effect for a period of time. After several minutes of LTFT relearn, they return to the pulsing/lower speed.


Any ideas on what causes this?

clinebarger

Activating Fan Relay #1 should run both fans at 1/2 speed, This runs the fans in series.

Activating Fan Relay #1, #2, & #3 should run both fans at full speed, This runs the fans in parallel.

Do you have it wired exactly like a '99-'02 F-Body?

Assuming it's wired correctly.....
Go into the tune & make sure that "recirculation fitted" is set to Fan #2 as a 2001 truck PCM will be set to A/C Recirculate which is incorrect for what your doing.