2002 Toyota Echo: won't start, flashing exterior and interior lights, beeps

[mw13068]

I have a 2002 Toyota Echo that won't start.

Symptoms:

1. When the key is put in the ignition, exterior turn signal lights begin blinking, and interior dash/radio/accessory lights blink in time with beeps.
2. Turning the key to the start position produces rapid clicks.
3. An error code reader (bought from Autozone) finds no error codes.
4. I tried to get the car to start with jumper cables, but I think the battery is too far gone for that.

Any ideas about what is causing this?

[mw13068]

Another symptom:

When the key is removed from the ignition, the blinking and beeping continues for at least 5-10 seconds and then stops.

I've tried disconnecting the negative battery cable and re-connecting it, and there is no improvement.

[mw13068]

The problem turned out to be a malfunctioning aftermarket alarm system that I didn't even know was there. It had apparently drained the battery as well as causing the chaos with the electrical system.

Luckily it was fairly easy to remove.