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No Display On Climate Control After Efan Pcm Upgrade?


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Ok I broke my own rule and messed with too much at once and now have no idea which area I created the problem in.


Ok its winter up here so my truck has been in the shop for months while I tinker.


My problem is I have no display from the autoclimate control. Nothing at all.

Here's what I messed with before it stopped working.


Pinned crank, installed upgraded maggie tensioner. Held off installing on the 3"pulley

Installed boost gauge (mechanical) I did not wire the light in. So I don't think I could have disturbed much here. And I checked all the harnesses under the dash that I worked near to route the Boost line.


Added Efans- Off a 05 truck or something from ebay. Used Blackbear performance harness, Wired into PCM. (I am certain pins are seated into ecm)

Swapped out original 105 amp Altenator for a 160amp- Purchased from alternator rebuilder who said it was the 140amp chassis but with different rectifiers to get 155-160amp.


After I was done, it had not been started in months, so I threw a charger on the batt before I hooked it up so it would have lots of juice. ( using efilive, I once thought I killed the ecm by flashing with a questionable battery, so I learnt my lesson)

Then removed the charger and hooked up a second battery to mine (like I was boosting the battery- just to double capacity if my EFILive tasks took too long).


Using Efi live I read and backed up the Pcm calibration. (this was redundant as I already had it backed up from after I installed the blower).


Then I re flashed the exact same calibration with only 1 change- I copied and pasted the fan parameters from an 05 silverado Fan Parameter table. Series/pararell fans, on and off temps, etc.


Then I started it.

and since I was going to hit the A/C to see if both fans would turn on before I gassed myself in the shop, but NOTHING< the entire display until doesn't show anything, but I do believe it kiced the Ac on as I heard the compressor go and ran out of the truck and both fans were going. The tiny lights in the re defroster light up, the re-cir, button lights, but the actual display is dead.


So I Reflashed it back to my original tune with no efans and still nothing.

So reflashed back the new file to make the e fans work and as expected still nothing on the climate control screen.


My truck is an 03 SS and from what I understand about pin 42 and 33 should BOTH be for the fans/ ac right? An 03SS shouldn't have that pin used for the Reciculating door or whatever it was on the older 99 trucks.



I have checked fuses, checked all the harnesses I may have disturbed while tinkering, I have not disconnected the e fan harness trigger wires to the PCM as this just happened and I didn't want to tear into it again.


Any idea?


Of course I searched. All I found was stuff on the climate control lights going out. could it have just decided to die now? (I do have 100k on it) Anyway to check this? Will the fan controls still work if the units display goes?


I'm going to have to dig into it more tomorrow, but maybe one of you have some insight that may save me a few hours.

Can't take it to the stealership for this!!!


Thanks in advance.


Edited by Fourtraxjay (see edit history)
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Pins 33 & 42 are for efan control ONLY; there are other PCM pins controlling A/C operation.


Since you have EFILive, use it to diagnose the problem! Use the bi-directional controls in EFILive and command the fans on & off; also command the A/C compressor on & off. Log the A/C pressure voltage (you have to make a custom PID to convert that to PSI, check the EFILive forum for the how-to); once you can monitor the A/C system pressure, go ahead and turn on the climate control "auto" switch (hit it twice to be sure) and turn the driver's dial all the way down (60-degrees) and in EFILive you should see the A/C system pressure go from about 30-psi to 100-psi (low-cool) and when the system goes into 'max-A/C' you should see the pressure go to around 200-psi. IMO if you see that behavior, then the climate control is working correctly and you have a dead display in your A/C interface module.


Mr. P.

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Thanks guys,


To silverSS- I actually had that brain wave hit me this am. Unfortunately when I ran out to see, it was indeed up.


Mr. P- I thank you for your advice. I will look into that, but EFILIVE is still quite un nerving for me to use.


I am a total NOOB at it. Most of what you mention, I understand by have no idea how to implement.


The EFI LIVE forum is so far over my head! I feel like I'm reading chinese sometimes. (which I cannot btw)


That is my only real complaint about Efilive. Not real user friendly for newbies (even those with computer experience). They give you all kinds of detail about how to install the program, which is easy as heck, then the manual skips right into the nitty gritty of tuning.

I understand engines very well, but always was limited to mechanical knowledge, so I thought getting efilive would be a good way to teach myself about V.E. tables and what not. Maybe I should have started with something easier maybe Hptuners?

BUT I knew right from the beginning I wanted efans, and efilive was to my knowledge the only one that could turn them on in the ecm.


I'll will poke around and let you know what I find.

If I try and use efilive to trouble shoot it, I'll probably be asking for more help.


Thanks for the help guys.

wish me luck.



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I have to thank Bill Gates for this one. After using his products for so long, I have develped a habit of starting all troubleshooting with a simple re boot.


Disconnected the battery for a minute. Hooked up it, Display on Climate control is good!


Thanks for the help guys.

I guess I will have to make a conscience effort to learn EFILIVE seeing as how this problem didn't force me to use it as suggested by the helpful mr. P.



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Glad all's good!!!


Don't get frustrated with EFILive, I know how you feel. I also am *still* going through the mind-shift of learning how to approach tuning in general, and different tuning strategies. I had to read a lot of EFILive forum and keep a bunch of notes before I started determining the best practices and also weeding out the bad practices. There is a steep "ramp-up" but once you get over that, the rest starts coming easier. Tuning takes a big investment of time to master, you need lots of hands-on experience as well as dedicated study. The other idea is this, it helps A LOT if you understand how the software that runs the PCM works, then you're not shooting in the dark with guessing what adjustment to make for any particular tuning issue...


Mr. P.

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