Mercedes-Benz CL-Class 2006 Owner's Manual page 486

Problem
The key cannot be turned in the ignition
lock.
Possible cause/consequence
The on-board voltage is too low.
Practical advice
Troubleshooting
Suggested solutions
Switch off consumers that are not re-
quired, e.g. seat heating or interior light-
ing, and try to turn the key again.
If this does not work:
Check the starter battery and charge it
if necessary.
or
Jump-start the vehicle ( page 497).
or
Consult a qualified specialist workshop.
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