I don't understand why you can't drive it though. I thought the ECU resets all codes when depowered. If it's still on even after disconnecting the battery, without starting the car, I'm not sure how a faulty sensor could do that without also causing a sensor code. I don't use a missing link but it sounds like yours has a vacuum leak.
2gnt: '99 RS-T, killed by a toyota, pending rebuild... Daily: Volt Daily #2: '99 EVG ebike- STOLEN by PEDRO