If you cant talk to the ECM there is a fair chance that the BCM has the same challenge hence no start. It the config is similar to other GM platforms the DLC connector and BCM dont see ECM CAN until it is passed through the TCM.Originally Posted by mbsurfersc
Taz & gmh308,
Both of those things make very logical sense.
gmh308,
I can talk to the tcm through the obd port either. The only thing is that i do not have a bench harness for that controller and have no way to get a cal into it. I guess the next step would be to buy that harness? Ill let you guys know
Not sure on Gen IVs ... definite communication issue ... assuming the T43 used CAN type communication ... is that the case also with the T42 ? Does your existing harness need be repinned to work with the T42 ? Seems that the TCM is probably the roadblock to commuication with the ECM (and starting) currently.
I'm old school and need to view things in print ... I always buy the Helm manual on these types of projects ... often a very simple solution will present itself.
Regards,
Taz
The t42 does communicate via can. The harness have is an adaptor deal that splices into the e38 harness. I have a feeling that the splices are in the wrong part of the can bus communication. I'm going to try moving those around and perhaps that will fix the issue.
Anybody know where i can get a bench harness for the t42?
EFI Connection ... was looking at those the other day.
Regards,
Taz
After going on there website it realized i had the connector on my e67 harness lol
so i flashed the tcm with the tune you provided taz and put it all back in the car.
Still the same thing... doesnt even turn over with the key
i went and jumped the relay and cranked it over, checking the basics.
I have spark but not injector fire. Seems to me like its the VATS. all of that is diabled in the ecm... Anychance another module could be doing this?
Haven't done a Gen IV conversion yet ... LS1-B guy. If I understand what Ian (gmh308) described, the OBD-II communication goes to the TCM first, when the other controllers after - not sure in what order (ie. ECM / BCM / ACM / ABS). It would seem that until the communications "path" is corrected, the vehicle is not going to start. That is, the VATS patch and other tuning in the ECM can't communicate with the BCM, etc.
Once all the modules are "talking" again, then your tuning (VATS patch, etc.) should allow the vehicle to start. My guess is that the problem is in how the T42 is currently wired into your existing harness.
Sorry I can't be of more assistance - out of my area of expertise.
Regards,
Taz
E67 connector into T42? T42 is a micro 64 connector and the E67/E38's are a finer pitch pin architecture again.....
The CAN linkage is typically:
ECM >>>>> TCM >>>>> EBCM/ABS >>>>> BCM >>>>> DLC >>>>> Anti Theft Controller etc Plus maybe an optional item like steering angle sensor if the vehicle has ESC/ESP.
So if your CAN does not have this continuity DLC to ECM it definately wont start. The crank command is generated by the BCM normally after it has said hello to the ECM the ATC the DIC/IP and the key and exchanged some "secret" messages and decided the car is not being stolen and the EBCM is functioning normally as well.
VATS will not bypass this process. VATS in the ECM is to enable coils and injectors without needing the BCM to say all is good to go.
Is your crank relay still connected to the ECM when you "hot wire" it?
Sorry Newbie here and you guys are way beyond me but I needed no less than 5 heavy gauge grounds to the motor all directly run to the negative terminal on the battery before the fuel injectors began firing. I had spark and crank but no fuel pumping. L92 with 4l70e. Such is the blessing of a non conductive all aluminum motor.
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