Dangeruss5.3

Hey guys. Im needing some help with my efans setup. I have an 01 Silverado 5.3 that I put fbody fans on. I got an aftermarket harness. I tuned it with efi live. As soon as you start the truck the fans come on and stay on low and will stay on until you shut the truck off. I did notice that when I add a 30 second delay it responds to it but it doesn't matter what I do with temp settings or a/c settings. I am running the 2 pin setup. I can control both of the fans with efi live and they work properly so I think that rules out any problems with wiring, relays, etc. I have been searching a lot and it looks like it might be an issue with the older computers or an OS issue. I just wanted to see if anybody had a confirmed fix for this. Thanks for the help.

Type of fans-series parallel fans
Fan #1 turn on temp-185
Fan #1 turn off temp-175
Fan #1 turn on by a/c temp-284
Fan #1 turn off speed-50
Fan #1 turn on speed-45
Fan #1 turn on delay-30
Fan #1 turn off delay-0
Fan #1 minimum on time-90
Fan #1 run on temp-284
Fan #1 run on time-1
Fan #1 a/c pressure enable-500
Fan #1 a/c pressure disable-500
Fan #2 turn on temp-195
Fan #2 turn off temp-185
Fan #2 turn on delay-0
Fan #2 turn off delay-0
Fan #2 minimum on time-90
Fan #2 a/c pressure enable-500
Fan #2 a/c pressure disable-500
Fan #1 and #2 both off-0

2002_Z28_Six_Speed

iTrader: (20)

This thread is old but what the heck....

What type of aftermarket harness did you purchase?
Does it have three relays?

What pins of the ECM did you tie into?


We could start with those questions.

Dangeruss5.3

Harness was from ls performance wiring. It has 3 relays and i used pins 33 and 42

1FastBrick

iTrader: (17)

I'm having the same problem with a fan harness from another vendor. Hopefully some one has an answer...

Trying to put 05 up truck fans on a 99 GMC 1500.

Tapped into the Same Pins Red 33 and Blue 42. Verified Pins are seated correctly and in correct spot.

Taped into the AC signal wire as specified, power and ground as specified.

Tried various settings within the tune.

Tried a newer 411 PCM,
Tried different operating systems,
Tried another Fan harness from the same vendor. First was a 2 relay harness, Current harness is a 3 Relay set up.


As soon as you start the truck the Fans run on low. Coolant has not even reached 100*F

I disconnected the AC pressure switch thinking maybe the pressure was to high. No change.

Dangeruss5.3

What a pain. I hope somebody can help.

1FastBrick

iTrader: (17)

I am beginning to think these things aren't wired correctly from the vendor. They confirmed my fan settings were good.

This has been going on a week for me. I even ordered a new harness and paid to have it sent Over Night on my dime to get this thing fixed as well as licensed another PCM on my Dime and ruled out it being a PCM issue...

Dangeruss5.3

That sucks. I would think my harness is ok because with koeo i can control the low and high fans correctly but maybe im wrong. I could be missing something.

1FastBrick

iTrader: (17)

I have the same control KOEO on mine.

I think the tiger control signal is wired backwards.

I have read the trigger signal is different on the 99-02 vs.the 03-up.

Dangeruss5.3

Hmmm something to look into for sure. I was actually just wondering the same thing.

1FastBrick

iTrader: (17)

I am not sure what else it could be.

I am going to try modifying an 06 fan harness I have and see if it works correctly. Then I will know for sure.