Thread: BCM bad
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Old 09-19-2017, 12:31 AM   #12
fdryer
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Join Date: Jan 2006
Location: NYC
Posts: 41,452
 

2003 L-Series 3.0L Sedan
Default Re: BCM bad

My bad as I didn't mention the bcm is for the L-series cars.

I'm not informed on what GM can do to used ECMs, BCMs or TCMs. All my knowledge is gleaned from here as members share info on repairs and service manual info.

As described in service manuals, GM explains replacing PCMs, ECMs, BCMs and TCMs with new blanks and programs them with their Tech II scantool. No mention is ever made in service manuals about using previously used modules and programming them. None. Here's where members have successfully installed a used bcm and return their car back to service. What's known are two things; used bcm retains mileage that cannot be altered and original remotes need to be programmed with the Tech II scantool to the new-used bcm to allow remote keyless operation. Passlock can be learned at home using a 30 minute procedure or GM's scantool in 10 minutes.

A bcm is not permanently married to its ecm/pcm. They're interchangeable. All electronics modules like the ecm/pcm and bcm are 'married' due to one thing only - Passlock factory security. A fuel password is exchanged between ecm/pcm and bcm during the remote Unlock and key on cycle. If I'm not mistaken, the ecm/pcm has the fuel password that doesn't change and the bcm is married/learned during factory line assembly. Once married, a driver simply uses the keyless remote to activate/deactivate Passlock using the Lock or Unlock remote pushbutton. pcm to allow the ecm/pcm to operate completely - startup and drive away.

With Ions, the starting circuit is disabled when security is active (security flashing quickly during starting). I do not know if Ions disable injectors and there may be one Ion member here that was able to troubleshoot his starting problem by checking if his starter turns over and having the engine run - a no start, zero starter problem. I think it was a damaged wire that took wiring diagrams to trace signals to find the wire damage. A very unusual problem because this wasn't a Passlock problem (security turned off during starting attempts). Even swapping in a used pcm was done to help repair this problem.

GM's dealer service and service manuals are not geared/written for the diyer and always use new parts. With programmable modules, this allows warranty for repairs and control over what's considered safe parts when they're new. Used parts are not warranted at all if GM and the owner are in full agreement that using used parts may not be successful while fees remain. Since Saturn has been discontinued, GM dealers are a little more open to accommodating Saturn owners requests. At this point it gets murky because there's little GM can do if using a used part other than verify it works and program passlock in 10 minutes. If there are any service bulletins to update a module, its incorporated at this time. Updates by themselves, to my knowledge from service manuals are for minor changes. Major issues that result from drivability issues are always handled as recalls like the ignition switch fiasco preventing starting. GM and dealers are loathe to state outright that used electronic module parts work. Members here in almost every forum have shown used modules work. Most doing it this way are not concerned with having remotes work or seeing a different odometer mileage. All they're concerned about is restoring their car's drivability for as long as possible for the least amount of repair costs.

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