2000 4Runner security light blinking

Which ECM did the dealer replace?

The one involved with the O2 sensors.

Without looking at a wiring diagram, I can't imagine why the security system light would blink when the vehicle is being driven after ECM replacement. Just curious, what was the problem that led the dealer to replace the ECM?

I recommend that you take the vehicle back to the dealership that replaced the ECM for diagnosis and repair.

I took the vehicle in to replace an 02 sensor - two replacement sensors failed to clear the check engine light, so the ECM was replaced at the suggestion of Toyota tech support. I went back to the dealer and asked about the flashing security light, and the only thing they could think of was to replace the battery in the remote :-(

Since I have the engine immobilizer, could it be that the ignition key was flashed to match a code in the new ECM, and the module controlling the security light thinks the key is bogus?

I asked why the ECM was replaced because ECM failure is so rare.

It is possible that the ignition key was flashed to match a code in the new ECM, but I would think that if the module controlling the security light thought the key was bogus, it wouldn't allow the vehicle to start. I think it is time for the dealership to make another call to tech support.

The ECM is in auto registration mode. This occurs after replacement of the ECM and allows the technician to quickly register the keys.

Ask the dealer to look up closing of auto registration and have all your keys handy. Check to see if any spares have been programmed yet. If not take them to the dealer when you return.

Let me know if I can further assist with this.

MDTDan

Problem solved - I found some technical information on the net, and all it took was to insert the key and depress the brake pedal 5 times.