After repairing a poor connection at the DLC on this 2000 Buick Century, click here to see , I moved on to the bigger problem of no communication with the BCM and no crank condition.
I went back to the splice pack under the driver’s side of the dash and located the purple wire, terminal “A” and the light green wire, terminal “M”. Using a jumper wire I connected the two wires. Then I connected my ohm meter to the purple wire at terminal 2 of the DLC connector and to the light green wire, terminal “A8” of the BCM C2 connector. I disconnected the BCM before testing the circuit to avoid feedbacks. There was no problem with the data line between the DLC and the BCM. Continuity was good and there was no short to either power or ground. I then proceeded to check power and ground inputs to the BCM. All were okay. The diagnosis is a faulty BCM. Including the data line there are 11 circuits that should be tested for problems. Too many to put in this repair. If you are attempting this diagnostic routine I strongly suggest looking at a wiring diagram in your shop data base or buying a subscription from Mitchell or AllData.
With the BCM reconnected and my jumper wire in place, I again checked for communication with the BCM. No communication, diagnosis of a faulty BCM.
I put the shorting bar back in the splice pack and checked all other modules for communication problems. There were no other problems.
By the way these modules are available as a rebuilt unit form ACDelco and they are fairly inexpensive.
There is an expensive snag in this repair though. A replacement BCM cannot be installed without a Tech 2 scan tool. At this time it is the only scan tool capable of performing a BCM Setup. In the BCM menu there is a section for Module Setup. A VTD Relearn also has to be performed. I used the TIS2Web GM software to perform this function.
There are two lines of setup functions, BPP (brake pedal position) and SDM (sensing & diagnostic module, airbag system) primary key in BCM. Codes in the SDM have to be cleared before this step will work. Sometimes the procedure will clear the codes and sometimes it won’t. Just easier to clear them first.
In the service programming system the VTD (vehicle theft deterrent) program is uploaded to the replacement BCM and you are instructed to wait ten minutes. At the end of the upload you should be instructed to turn the key off for at least five seconds. After that period the engine should then start when you try to crank it.
I should note that on this particular vehicle the BCM Setup would not work until the VTD was performed. I do not know if it is me or not but I think GM changes the routine. It seems like the order of programming events is never exactly the same. Of course it is very rare that I am programming the exact module in the exact car on the same day. More than likely it is just my mind not keeping up.
The setup procedure has been started.
Now it is completed. It really is not that hard but you have to have the scan tool and TIS2Web programming subscription to replace a BCM.