My project is an LY6 with a straight drive into a 72 GTO, so no TCM. This isn't really a problem so far, but I would like to control the electric fans by the ECM. Unfortunately the 158mph default is higher than whatever the max speed for fan enable is. Is there a way to access this parameter or request it be added? Thanks,
Jon
Needs to have a manual trans ECM OS if you want that to work. It's an OS issue, not something that can be changed in the tune. The auto OS looks for speed comiing from a TCM over CAN lines, the manual OS has VSS wired direct to the ECM.
Post a tune.Originally Posted by Jontheelectrician
I think there are several ways to resolve this:
- enable VSS in the ECM and switch vehicle speed source from GMLAN to it, optionally enable all diag infrastructure around sensor input if you have sensor connected.
- set default (no comm) speed to 0
- change fan vehicle speed limits
2011 Cadillac Escalade L94 w/LS3 valves and valve springs
Thanks for the quick responses. I'll try not to make this too long, while not leaving anything out.
Just for the record the rundown of the car is:
1972 GTO, 3 speed (factory), 6.0 LY6, E38 Ecm (matches engine), t4 turbo
Not fast, just something to teach my kids how to do donuts and burnouts in.
It seems like with a swap there are always trade offs for time/money/performance/ease. I am using the E38 truck ECM because I pulled it from the donor as a working system to try to keep things simple(ish). I knew from reading other peoples woes with the 158mph reading without a TCM, and am okay with the limitation of no VSS. Driveability is more than acceptable for this car. I have not upgraded the injectors yet, so only minimal boost (2lbs is wastegate minimum) while I get all the kinks out of everything else. The attached tune is what is in there right now, I just put the 2 bar MAP sensor in yesterday and I haven't done anything with it yet. None of this really a problem yet though.
The real question is about the speed enable/disable for the fan control for this ECM. Since the ECM defaults to 158mph with no TCM, that is above whatever speed the factory tune disables the fans, so end result is no fan control. Other tunes are able to change this parameter, but not this one it seems. That is what I would like to request is access to this setting if possible. If not, I can just go old school and put a temperature switch on the engine and be done with it, but of course the more elegant solution would be to fix it in the software side.
Hope that makes sense.
Jon
The way to fix it in the software side is to get the ECM reprogrammed with a manual trans ECM OS (2008 Corvette?), and then wire a VSS in on the same pins the Corvette used.
I was initially going to do that, but then I would have pedal and throttle body problems, no VVT, more credits, etc. Seems like alot to avoid a small problem.
Temp switch is cheap enough and would take care of it if this is not an option.
Try this one. I've changed System segment, but you will not see any differences with Compare function.
1972gto2barvss_fan.hpt
2011 Cadillac Escalade L94 w/LS3 valves and valve springs
You can check to see if verlon's fix will work but this has been gone through before. Your best solution is the Corvette OS/ECM/trans combo. 2008 or 2009. Reason not a later model is the permanent code issues
Sweet! Thanks, I will as soon as the snow gets outta here. I will post up what happens. Thanks
Results are in:
I just tried Verlon's adjustment (thank you again), and the speed now shows 0, awesome. So I let it warm up to 212 or so, but no fan activated (tune is set for 203). I can confirm that I can activate the fan from the scanner in the vehicle controls section, and it functions. The PID will also indicate the on function when I do this. Maybe I have missed something else in the fan settings?
Where do I learn about the system segment?
Thanks,
Jon
Oh, you forgot to set fans output control.
fan.png
Unfortunately, nowhere. This knowledge is gained by pieces mostly from reverse engineering and collecting leaked GM documents.
System calibration segment contains settings of the ECM 'neighborhood' - from simple BARO sensor equipped option, brakes, fans, drivetrain configuration (transfer case type and so on) to GMLAN settings.
What I've done is just disabled one of the GMLAN messages from TCM, which contains output shaft speed data. Loss of this message leads to setting of the internal ECM VSS failure flag and use of defaulted VSS value (158mph) even when Trans Type option is set to Manual.
2011 Cadillac Escalade L94 w/LS3 valves and valve springs
Got it, I will give this a go. I looked at that table several times and couldn't make heads or tails of it. I will have to try it tomorrow after work.
I understand, that type of information is hard to come by. Thanks for sharing just a bit.
Jon
Following up on this. Fans work fine now after adjusting the output control table. Just to be prudent, I changed back to the tune with the original system sector as well, and the fans also work. So turns out that it was my ignorance of the output control table that was messing me up.
I am checking out the other differences with speed=0 as I get more time. Throttle response tables and coastdown, etc are all impacted. This is definitely useful. Thank you for the time.
Jon
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