Weird problem with PCM and EFans

[01Blackerado]

has anyone ever seen an issue where the PCM is contantly grounding pin 42 (low fan switch). Everytime I turn the truck on, the fans kick on immediatlely instead of waiting for the Fan on time programmed in my tune. I thought maybe it was a problem with the relays but then i put a volt meter to the wire that is curretnly in 42's slot and it was definitley showing a grounded connection. If anyone has any idea as to why the pcm would basically have the fans on at all times when the vehicle is running please let me know.

01 chevy silverado ecsb ... not stock by any means

Heres the tun incase you would like to see if it is the problem but im almost positive that it isn't

[01Blackerado]

ok this issue is getting weird. I removed all the physical connections from the A/C switches that go into the red harness 11 / 17 / 43 / 55. Even with these signals removed physically from the Red harness Im still seeing a ground connection to the Pin 42 blue AND 33 red which are used for Fan low and high. Someone suggested that there could be a corruption with the tun file!? Can anyone help please cause this is starting to wear me down.

Here's a link to the entire thread I have been discussing on PTrucks.net

http://performancetrucks.net/forums/showthread.php?t=478841

[ChipsByAl]

Just in case something went bad in the file, start with a known stock file for your truck and transfer your mods on over. Also fix the out of range parameters while you are at it. You may want to paste and copy the fan control parameters from a stock 2001 F-car and only change the turn on/off temps. Make sure no DTC's are setting.
Al

[01Blackerado]

I took these fan settings from the 2002 Z06 ... the one that come with V7.5 when you install. Then I changed the on temps for the fans that was it. Im getting a ground connection signal from 42blue and from 33red even when the Key is on Engine off!!

The other bad thing is that I dont have a stock tun for my truck anywhere... and if I did I would be hard up for the same OS that carried a 4L80e transmission. That was what caused me to get a 6.0 with 4L80e already in the PCM.

The thing is though, this has been happening prior to the swap!! So on my stock 5.3l with 4l60e I had this same issue. Just always thought it was a problem with the PCM and it would go away once I swapped to a new pcm...

Oh and another weird part, I dont know if this holds any significance but, I also cannot use the Bidi controls to turn the signal off and on! No matter what i do, as long as the key is in the on position whether engine off or engine is on, Pin 42 blue and pin 33red are receiving ground from the PCM

[01Blackerado]

Does anyone know of someone at EFiLive that i can send my tun too? Aparently this is an on going issue with the OS for 99-02 trucks! The HPT guys are or were having the same issues but they sent the tun to "Bill@HPT" and he was able to fix something in the OS that corrected this issue!! Who at EFiLive is like Bill from HPT?

[turbo_bu]

Not sure exactly how you configured the electric fans, but guessing that you did a Fan segment swap to get the functionality in the truck OS. One thing to check is the wiring pin outs. You say you are trying to use 33 and 42 (Blue) which are currently grounded. I only have an F body wiring diagram, but for an 01 F body, pin 33 is Cool Fans 2 & 3 Relay Control; pin 42 is TCC Solenoid Valve.

Maybe when you do a Fan segment swap, it is linked to the pin outs of the one you are swapping from?

[01Blackerado]

Naaa its not a segment swap!! The truck PCM already has this built into the program. All you have to do is turn the feature on. For us 42 BLUE is fan and 33RED is A/C recirculation OR fan #2 or in the case of a series setup, its the HIGH control for the fans

[Chevy366]

Unplug the temp switch signal wire see if it stops .

[01Blackerado]

Ill try, but i dont think its the issue...only because i cannot BIDI them off either... I believe its an HVAC issue somewhere. A long time ago I blew the first harness somehow and when that happen i got codes B1000 and U1500, i thought these codes were due to a bad PCM since something obviously happen. I then bought another PCM and i dont have the codes but i still have the problem. I believe it will end with me tracing back what blew within HVAC when these codes tripped on the old PCM

[GAMEOVER]

I had a few problems like this before....Try setting FAN#1 temp settings 10 degrees colder than FAN#2....ON & OFF Settings
The only OS I could make the fans work like they should was to Full Flash a 2002 OS 12212156 into a 1999-2001 PCM, it's a pain but thats the only way I could get it to work.

[Chevy366]

Once wired to the PCM the A/C compressor wire is not needed , it is a 12v positive wire anyways (green/white) , light green key on positive A/C if I remember right .

[01Blackerado]

I had a few problems like this before....Try setting FAN#1 temp settings 10 degrees colder than FAN#2....ON & OFF Settings
The only OS I could make the fans work like they should was to Full Flash a 2002 OS 12212156 into a 1999-2001 PCM, it's a pain but thats the only way I could get it to work.

Ok Im going to check for that OS...I have an 01 PCM though from a suburban 2500

[01Blackerado]

Ok so I tried the OS you mentioned but it wont let me write it to the PCM am I missing something?!? It says that it has to match the current OS that the PCM has.

[01Blackerado]

Ok, update, ran that OS with Full Flash and still had the exact same issue. Damn this really blows, Im pretty sure theres a short somewhere then. Anyone know of a wiring diagram i can try to follow so i can see how HVAC communicates with the PCM!? When that old harness blew out and i got those codes i think something electrical went with it. I just need to find out what and where it is. Seeing that U1500 can either be HVAC code OR onstar im going to assume that HVAC is the issue since i doubt onstar would kick my fans on lol

[01Blackerado]

Actually, does anyone know if the BCM has anything to do with this??? Being that i got B1000 DTC and U1500??