FJCruiser Error Memory Lock Undervoltage

The 'fault memory lock' indicates a deeper problem than just a logged error. Undervoltage can trigger it, but it usually locks due to a critical ECU malfunction or a security breach attempt. Have you recently had any electrical work done, or noticed any other unusual behavior?

No recent electrical work. Unusual behavior? The only thing I can think of is that the battery was completely drained a few weeks back. Could that have initiated the lock?

A fully drained battery could very well be the culprit. The ECU might have interpreted the voltage drop as an irregularity and locked itself as a protective measure. It's difficult to say definitively without diagnostics. A workshop visit is advisable to unlock the control unit and properly diagnose the underlying cause. Expect a diagnostic check and potential unlocking fee.

Thank you for the information. I had the FJCruiser checked at a workshop; the undervoltage had indeed triggered the lock. The total repair cost was 240€.