2nd stock ecm for 4l80e control?
10-13-2014, 11:00 AM
#1
2nd stock ecm for 4l80e control? im planing to use this extra ecm as a tranny controller for my 4l80 swap on my BS ctsv os.
what i need to know is what inputs must the ecm see to control the tranny? will the 2nd ecm need to see a full boost table or can i get away with a sd 100kpa table on the tranny and a 3 bar for the car?
also what sensors must the 2nd ecm see to run correctly shared or stand alone
what i need to know is what inputs must the ecm see to control the tranny? will the 2nd ecm need to see a full boost table or can i get away with a sd 100kpa table on the tranny and a 3 bar for the car?
also what sensors must the 2nd ecm see to run correctly shared or stand alone
10-13-2014, 07:21 PM
#4
Moderator
I have no idea what you are doing...
What ECM or PCM is controlling the engine?
What is your "extra ECM"?
An ECM is an Engine Control Module, it cannot control a trans.
An older PCM is a Powertrain Control Module, it controls both the engine and the trans.
A TCM is a Transmission Control Module. A 6L80E has the TCM built into the pan. You can buy a separate T42 TCM (about $100 on ebay) which can control a 4L80E.
A TCM does not have input sensors from the engine, it receives engine information from the ECM over the CAN-Bus (Car Area Network) which is a digital stream.
Even after you answer these questions I likely will not be able to help you, but an ECM/PCM/TCM expert might.
What ECM or PCM is controlling the engine?
What is your "extra ECM"?
An ECM is an Engine Control Module, it cannot control a trans.
An older PCM is a Powertrain Control Module, it controls both the engine and the trans.
A TCM is a Transmission Control Module. A 6L80E has the TCM built into the pan. You can buy a separate T42 TCM (about $100 on ebay) which can control a 4L80E.
A TCM does not have input sensors from the engine, it receives engine information from the ECM over the CAN-Bus (Car Area Network) which is a digital stream.
Even after you answer these questions I likely will not be able to help you, but an ECM/PCM/TCM expert might.
Last edited by mrvedit; 10-13-2014 at 07:44 PM. Reason: Correction about the TCM on a CTS-V
10-13-2014, 11:45 PM
#5
I have no idea what you are doing...
What ECM or PCM is controlling the engine?
What is your "extra ECM"?
An ECM is an Engine Control Module, it cannot control a trans.
An older PCM is a Powertrain Control Module, it controls both the engine and the trans.
A TCM is a Transmission Control Module. A 6L80E has the TCM built into the pan. You can buy a separate T42 TCM (about $100 on ebay) which can control a 4L80E.
A TCM does not have input sensors from the engine, it receives engine information from the ECM over the CAN-Bus (Car Area Network) which is a digital stream.
Even after you answer these questions I likely will not be able to help you, but an ECM/PCM/TCM expert might.
What ECM or PCM is controlling the engine?
What is your "extra ECM"?
An ECM is an Engine Control Module, it cannot control a trans.
An older PCM is a Powertrain Control Module, it controls both the engine and the trans.
A TCM is a Transmission Control Module. A 6L80E has the TCM built into the pan. You can buy a separate T42 TCM (about $100 on ebay) which can control a 4L80E.
A TCM does not have input sensors from the engine, it receives engine information from the ECM over the CAN-Bus (Car Area Network) which is a digital stream.
Even after you answer these questions I likely will not be able to help you, but an ECM/PCM/TCM expert might.
10-14-2014, 12:43 PM
#6
my car(04 green/blue ecm) has a odd ball os that has no code for a auto tranny abd cannot be seg swaped to work. i with use a 2nd ecm of the same year control the tranny without the need for a new os on the ecm that came in the car.
basicly im going to use the 2nd ecm as a standalone tranny controler and save my self 600$ on a aftermarket one.
ps in the 24X ecms there is no tcm. its all built into the one box
basicly im going to use the 2nd ecm as a standalone tranny controler and save my self 600$ on a aftermarket one.
ps in the 24X ecms there is no tcm. its all built into the one box
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10-14-2014, 07:03 PM
#8
thats basically what im doing. i will run a file from truck or something that came stock with a 80e on the 2nd ecu. just looking at how to wire and tune the 2nd ecm.
im not sure what sensors the ecm will need to see for it to work rght. and if it will need to have a 2bar file in it same as the car or can i get away with just a stock file
im not sure what sensors the ecm will need to see for it to work rght. and if it will need to have a 2bar file in it same as the car or can i get away with just a stock file
10-14-2014, 07:48 PM
#9
Moderator
I seriously doubt you can use a 2nd PCM (technically it is not an ECM) to control just the trans. IMO, at a minimum the PCM needs to be hooked up to the crank sensor and TPS to even be "alive". Likely it also needs to be connected to the injectors and coils before it begins to function correctly. Even then without a cam sensor, MAP and other inputs and outputs it will throw so many codes that the trans might be disabled. Even on a normal car various codes will cause the PCM to put the trans into "limp" mode and refuse to shift it. Actually as I write that I am ready to bet you $100+ that it will never work.
Remember that you cannot connect any of your existing sensors to two PCMs in parallel. Therefore, you might even have trouble connecting an aftermarket trans controller as it will need at least TPS and VSS input and your existing PCM needs those too. Your '05 PCm does not have CAN-buss support and therefore cannot share the TPS/VSS and other values with an external trans controller.
You might find that a '08+ ECM can control your engine and then use the GM TCM. However as you probably know the late model ECM only work with 58x and DBW.
While very expensive, one solution might be something like the Holley Dominator EFI controller which can control even 1000+ HP engines with various adders and a 4L80E. It supports 24x and 58x, DBC and DBW. It sure is on my "wish" list.
Remember that you cannot connect any of your existing sensors to two PCMs in parallel. Therefore, you might even have trouble connecting an aftermarket trans controller as it will need at least TPS and VSS input and your existing PCM needs those too. Your '05 PCm does not have CAN-buss support and therefore cannot share the TPS/VSS and other values with an external trans controller.
You might find that a '08+ ECM can control your engine and then use the GM TCM. However as you probably know the late model ECM only work with 58x and DBW.
While very expensive, one solution might be something like the Holley Dominator EFI controller which can control even 1000+ HP engines with various adders and a 4L80E. It supports 24x and 58x, DBC and DBW. It sure is on my "wish" list.
Last edited by mrvedit; 10-14-2014 at 07:53 PM.
10-14-2014, 08:19 PM
#11
Piggybacking ECM/PCM's has been done in the past. I'm actually piggybacking a couple of Megasquirts on a project at the shop now.
I know using the old 727 ECM's from the early 90's has been done.
Going from memory when you use the sensors to signal two contol modules, you have to "step up" the signal which involves using a resistor in the circuit.
We commonly piggyback the TPS signal to run standalone trans controllers with OEM or aftermarket engine controllers.
I think your project is possible, but it's going to be a huge pain in the neck.
At a miminum you would need VSS signal, and TPS. You could tune out most of the other codes and inputs. You could additionally use CKP, trans pressure switch, and ISS and get closer to a stock type control.
I know using the old 727 ECM's from the early 90's has been done.
Going from memory when you use the sensors to signal two contol modules, you have to "step up" the signal which involves using a resistor in the circuit.
We commonly piggyback the TPS signal to run standalone trans controllers with OEM or aftermarket engine controllers.
I think your project is possible, but it's going to be a huge pain in the neck.
At a miminum you would need VSS signal, and TPS. You could tune out most of the other codes and inputs. You could additionally use CKP, trans pressure switch, and ISS and get closer to a stock type control.
10-14-2014, 08:22 PM
#12
Moderator
The crank, cam and MAF sensors are even more complex; they are actually electronic circuit modules; I have no idea how eager they are to share their complex signal with two PCMs.
Even then what are you going to so about the missing injectors and ignition coils.
10-14-2014, 08:31 PM
#13
It likely is more complex than that. Take the TPS. It consists of a resistor sitting between +12V and ground. The signal lead then slides on this resistor and returns a value between about 0.25 and 5.0 volts depending upon throttle position. You can hook up a volt meter and measure it while the engine is running because the volt meter has a very high "impedance" which doesn't affect the signal value. However, I don't know what the impedance of another PCM is, if it is low it will change the value, e.g. instead of 5.0 volts it might read 4.0 volts. (Or perhaps the PCM is supplying +5.0 to the TPS and not +12V. If the PCM is reading current through the TPS and not voltage, you are completely SOL.)
The crank, cam and MAF sensors are even more complex; they are actually electronic circuit modules; I have no idea how eager they are to share their complex signal with two PCMs.
Even then what are you going to so about the missing injectors and ignition coils.
The crank, cam and MAF sensors are even more complex; they are actually electronic circuit modules; I have no idea how eager they are to share their complex signal with two PCMs.
Even then what are you going to so about the missing injectors and ignition coils.
If he ties into TPS, puts the VSS signal into the additional PCM, gives it power, switched power, and ground like stock, it should work. I don't think it would even need CKP if he tunes all the engine related codes out. Pretty much kill all the tables not related to the transmission.
He could run into some stuff that would need the code tweaked by the tuning software guys.
10-14-2014, 09:04 PM
#14
thats kinda what im thinking.
all the stuff that plugs into the tarnny will all go to the 2nd pcm.the vss,tps and some sort of rpm signal i would think but not sure where to pick it up from.
would a map sensor be needed to make the tranny happy?
i know im shooting for the stars here but i dont see why it wouldnt work.
all the stuff that plugs into the tarnny will all go to the 2nd pcm.the vss,tps and some sort of rpm signal i would think but not sure where to pick it up from.
would a map sensor be needed to make the tranny happy?
i know im shooting for the stars here but i dont see why it wouldnt work.
10-14-2014, 10:25 PM
#15
Moderator
Glad that Jake has experience with this and is chiming in.
One issue to think about is the trans line pressure which is adjusted by the PCM according to engine load. I suspect the load is calculated from some combination of TPS, MAP (and or MAF if connected) and perhaps injector flow rate. The TPS by itself might not be enough. And if you get it wrong you will ruin the trans. Better for Jake to do such experiments than you.
The megasquirt (engine controller) and megashift (trans controller) are very informative sites. Since these are basically open-source "kits" (solder your own circuit boards or buy fully assembled) the full electronic schematics are available and all variations are documented in the forums. Even if you have no interest in these controllers a huge amount of very technical info is available here.
One issue to think about is the trans line pressure which is adjusted by the PCM according to engine load. I suspect the load is calculated from some combination of TPS, MAP (and or MAF if connected) and perhaps injector flow rate. The TPS by itself might not be enough. And if you get it wrong you will ruin the trans. Better for Jake to do such experiments than you.
The megasquirt (engine controller) and megashift (trans controller) are very informative sites. Since these are basically open-source "kits" (solder your own circuit boards or buy fully assembled) the full electronic schematics are available and all variations are documented in the forums. Even if you have no interest in these controllers a huge amount of very technical info is available here.