I picked up this beautiful, albeit somewhat ignored 2006 Z51 from a woman who lost her husband about a year ago. The car was his and she knows nothing about it. As such I’m doing my best to figure out what’s been done to the car and bring it back to her glory days.
As I’m sorting it out I’ve run into a situation that has stumped me and everyone that I’ve reached out to locally. This is keeping me from really doing anything else until I figure it out. So I’m now reaching out to you all in hopes that someone has experienced this, knows someone that has and hopefully has some thoughts on what I need to do, where I need to look, or what I need to test.
The fan, and it’s a single fan, is still not working with the temperature, (or by controlling it from the laptop), however it does work with the AC. I’ve replaced the Fan Control Module, (with a GM replacement), nothing! Tested the circuit back to the ECM, & determined it to be the culprit. (It was a bit strange strange that in our circuit testing when we unplugged the connector to the ECM the fan came on, on low. Plugged it back in, nothing!)
I ordered and rec’d a refurbished ECM from Flagship One and plugged it in, (before reinstalling it), and controlling from a laptop it ran! So we buttoned it up behind the wheel well thinking all was well. Reloading the Tune that was in the car when I got it , (new ECM came with the factory tune for my VIN), fan not working again. Again the fan comes on with the AC but we can NOT get it to come on controlling it via the laptop.
Any ideas- please! I have reached out to Flagship One and waiting for them to reply. Thanks from a very frustrated old man!

 

Would flash the OEM tune into the ECM, and see if that solves the problem. If it does, then you know that problem is in the after market tune.

Hence turning on the HVAC will have the ECM kick the fan on to start by itself to draw air through the HVAC heat exchanger in front of the raditor, so we know that the PWM and the ECM wiring side is fine since that is happening.

On the engine temp side, you have the water temper sensor gauge in the drivers head that ecm that should be reading that, and depending on what the engine temp percentage and rest of the tune commands are, should be turning the fan on when the engine reaches that temp.

So stock fan temp table values,
Attachment 48335485
But not the only commands in the tune that will either turn the fan off/keep it from coming on isntead.
Hence temp tables values may be fine, but you have another command value screwed up that is telling the fan to stay shut off instead.

As for tune, if EFI live or HP tuner (what tuning software I have on hand), if you want to post it, we can take a look through it to see what value table is screwed up/preventing the fan coming on from the engine temp commands.

 

Thanks VERY much Dano523! I’m actually working with a very knowledgeable LS mechanic, and good friend. I will ask him to take a screen shot, of the tuner program as you suggest. Pretty sure that he’s using the HP tuner and I’ll send it on what I can.
As soon as I get it I’ll post, this issue has been very frustrating as it’s holding me back from working on the many other minor improvement opportunities. Thank you VERY much helping me out.
Back to you soon!

 

Have him make a copy of the tune (HP tuner format), and just give me a link to open it up with HP tuner.

Chances the temp tables are fine, and it just one of the other setting that shuts the fan off (like higer revs) that is wrong/stopping the fan from coming on with the temp tables itself.

 

I'm having the same problem and I'm wondering if this was fixed

 

I don’t know much about these systems so please don’t flame too hard if this is a dumb observation:
Often when fans come on with ac they come on high. Maybe there is a problem with the low speed wiring? (Assuming we have separate wiring).

I know the wiring often gets burned at the connector at the module.

 

My fan won't even come on when the AC's on... But I know the fan works cuz I can hotwire it. I checked the connections. Nothing looked burnt, I'll assume it might be the ECM wire... I'll continue to dig and report back...

 

Check the ground pin on the fan controller connector. The ground pin usually burns out and you will need to run a new ground.