LQ4 Cooling Fan on all the time

[dgold]

Hi, I recently swapped in a 6.0 LS in place of my 8.1 to see if I can adjust to a lot less power in favor of better fuel economy and my cool fan is now staying on al the time. I don't think it's a wiring issue as I've used this harness before without this issue. The ECU is from a 5.3 and is all I had laying around and my local boneyard didn't have any 6.0 ECUs on the shelve. I copied over pretty much everything from a stock 6.0 file and made a few mods from there. I'm running a stage 1.5 cam and stock 8.1 injectors, so nothing too wild. I just made a few adjustments and haven't driven it but around the block, so I know it will need more tuning. Anyhow, I copied my fan settings from the 8.1 into the fan tab and don't know of any other places that could affect the fan operation. If someone could take a peak at the file and let me know what you see that isn't correct, I'd appreciate it. Thanks

[edcmat-l1]

Need to scan it and make sure the coolant temp sensor isn't causing it.

[blindsquirrel]

Or the AC pressure settings, since '99 used discrete switches instead of a sensor.

[dgold]

The coolant temp seems to be reading properly in scan mode.

[kevin87turbot]

Some of the early 1999-2000 OS's don't play nice with e-fans. I've had a few with the same issue that yours has. I just updated to a later version OS and fixed the issue.
I don't recall ever seeing the issue on the 2001-up OS's. If you need to keep a 99 model OS, the 12212156 OS seems to work much better.

[dgold]

I'm an old guy that struggles with tuning as I don't do it enough to remember all the technical skills. Can I flash or copy in a newer operating system or do I need to start from a newer ECU?

[RDF1]

Some of the early 1999-2000 OS's don't play nice with e-fans. I've had a few with the same issue that yours has. I just updated to a later version OS and fixed the issue.
I don't recall ever seeing the issue on the 2001-up OS's. If you need to keep a 99 model OS, the 12212156 OS seems to work much better.

Same here '99 and '00 OS's will do weird stuff with E fans. Sending the 12212156 OS into them and no problems at all.

[Alvin]

If I can remember to check this thread again when I'm at my desk I'll do a fan patch for you. You might be able to download it off our website. From my foggy memory setting it up as AUX fan is the ticket on the odd early trucks.

[mbray01]

On the early operating systems, ive never had one keep the fans on, the issue was always not operating the fans at all. Now having said that, the fans running continuous in my experiance is either the ecm is in a default condition(could be from your mixing and matching components from different files) or wiring issues

i would load a stock 02 5.3 file in with fans enabled, and see what it does

[dgold]

I changed to a evu from a 01 Tahoe. Problem is gone now. I'll just sell the other one for use in a 1999-2000. Thanks to those that took the time to reply!