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Hi all, I have been getting a security light on my dash along with DIC B2721. Cleared the code, but it returns the next drive cycle. Car starts and runs fine. What I have tried so far is; cleaned the ignition switch, tried multiple keys. The battery voltage is 11.9-12.2 with the ignition on, but not running. 13.9-14.2 when running. My car does have some type on column lock bypass, but not an LMC5.
It's worth checking the documentation on the column lock bypass device you have, this could be related to it.
Pages 8-727 and 728 cover this in the 2000 service manual. Since you're having the issue with multiple keys your ignition switch contacts are probably dirty or worn. Next step is "Ignition Key Lock Cylinder Test".
What sets the DTC is the BCM detects the “signal circuit is one of 15 valid but incorrect resistance ranges”….I would try cleaning the key pellet with alcohol and if you have another key try that and you could try measuring the resistance of both keys..the resistance should be close to one another…there are only 2 wires that go to the BCM so that wiring may have to be inspected…if you need help and you live near State College I can recommend someone.
B2721 Code
