Only a Valet key got Gen1? Here's my story

Change Immobilizer transponder (ICU) in Gen1 / Classic Prius.

Ok, so I have a Gen1 Prius (call it V1) for which I had only a valet (Toyota grey) key. Nervous state of affairs.

Then, I got access to a (mechanically dead, electrically okay) Gen1 Prius (call it V2) which had at least one working MASTER (black) key. Having an operational Prius with only one functional key is bad practice, so I was thinking about how to generate additional functional keys for V1 without purchasing the entire immobilizer/lockset kit from Toyota (about $500).

Aha, says I, I says, I can swap the immobilizers, use the V2 Prius master key to train the V2 immobilizer with the V1 Engine Control Unit (ECU) after I move it to V1. After that, I can then add additional master or sub keys to V2.

Well, doing research (and having painfully extracted the immobilizer from donor V2 Prius), getting to the immobilizer ICU is HARD - by design - and there is no published procedure on how to do it.

Art’s Automotive published an outline (Art's Automotive), but is short on details.

So here’s my effort at a procedure that should lessen the pain of the process.

Doing the Immobilizer Swap:
Estimated time: 4 hours
Tools needed:
10mm socket, 10mm deep socket, 14mm socket (all, 3/8 drive)
10mm wrench (ratcheting is strongly suggested)
n=2 6in socket drive extensions
#2 Phillips screwdriver
Long-nose pliers
at least one small flat head screwdriver
6 small containers (to hold various screws)
12v Battery charger
Flashlight (Very helpful for Step 16)

Parts needed:
replacement immobilizer(ICU)(immobilizer part #89780-47010)
PLUS one master key for that immobilizer
at least one non-chip key cut for Accepting/Target vehicle
at least one blank master (Type TOY43AT4) key cut for Accepting vehicle

PROCEDURE: (yeah, it's long, but...)
In the Accepting vehicle:
(1) In the trunk: remove the ground connector (negative) from battery to the chassis. Keep it isolated.
This puts the Accepting/Target Prius “under anesthesia” for this job.
(2) Start charging the battery (while the rest of the work gets done).
(3) Passenger compartment,: unplug 2 wire sets from under the driver’s seat.
(4) Use 14mm socket, remove 4 screws securing the driver’s seat, and remove it from the car.
(this is to make room for working, later on. You will thank me for this tip. Eventually.)
(5) Use 10mm socket, remove 2 screws and lower kick panel under the steering wheel. There are 2 cable sets on the left side (mirror control and dimmer control), plus the OBDII port cable set, and one on the right (cabin air temperature sample hose) which will need to be disconnected. Use the #2 Phillips to remove 2 screws from the hood release latch.
(6) Use #2 Philips screw driver, remove 3 screws from cowling around steering column. You may need to insert the key in the ignition and turn the steering wheel to get access to 2 of the 3 screws).
(7) Remove any key from ignition.
(8) Remove the lower steering wheel cowling cover.
(9) Use #2 Phillips to remove (from below) 1 bright yellow screw near the ignition switch which will allow the upper steering wheel cowling to be removed. Then remove the upper cowling.
(10) Use 10mm socket, remove 2 screws from metal kick panel reinforcement panel; remove panel.
(11) Use 10mm socket, remove 2 screws from metal vertical member left and slightly below the level of the steering column; remove the member.
(12) To the right and below the steering column, edge on and vertical, is the Engine Control Unit (ECU). Unplug 5 cable sets; unfasten 2 cable ties holding the cables onto a bracket at the back of the ECU. Long-nose pliers are helpful here.
(13) Using 10mm deep and 1 or 2 extensions, unbolt the ECU and remove it.
(This makes room for your hands to perform Step 18).
(14) Use 10mm wrench, remove the one bolt holding the bracket for the Door Remote Control (DRC).
Disconnect the DRC cable and set the DRC aside.
(15) From the ignition switch, find the 2-wire RFID Sensor connector cable, and disconnect it from the ignition switch. Follow it under the steering column and disconnect the 2 cable clamps which secure this cable to other assemblies, so it hangs free. Remember this routing.
(16) Follow this cable into the darkness until you encounter the Immobilizer Control Unit (ICU).
(17) Use 10mm wrench, remove one bolt holding the ICU bracket.
Here is where the ratchet wrench pays for itself.
(18) Unplug the ICU from the main cable harness. It’s a white plug, 12 wires in the cable. Look at the replacement that you have as a guide. You will likely end up on your back, under the steering column, using both hands. Large people are definitely disadvantaged for this task. It’s why we removed the driver seat. It is a locking connector; depress the locking tab to unlock, and at the same time pull the cable and ICU apart. If it doesn’t separate easily, the tab isn’t fully depressed. Patience, young jedi.
(19) Work the ICU carefully out of its position and into your lap. Don’t damage the long lead that you disconnected from the ignition switch. Remember how that cable was routed.
(20) Mark this unit with tape or something that identifies it as the OLD unit.

This is about the halfway mark. Take a break; have a refreshing beverage.

(21) Position the NEW ICU back in the steering column space; connect the white 12 pin connector.
This may take a while. Be patient. The “click” of success is very satisfying.
(22) Route the 2-pin Sensor connector cable back under the steering column, restoring the cable clamps, and connect the free end to the ignition switch RFID Sensor coil connector.
(23) Use 10mm wrench, replace one bolt for the ICU bracket to the frame.
(24) Connect the DRC (Door Remote Control) with its cable.
(25) Use 10mm wrench, replace one bolt for the DRC bracket to the frame.
(26) Connect all 5 cables back to the ECU.
(27) Use 10mm deep socket, bolt ECU back into place.
(28) In the trunk, reconnect the negative ground lead from battery to chassis.

Now, we test our work and train the ECU to recognize the new Immobilizer (ICU).
TEST, before all the parts go back, and the car is reassembled.
(1) Place the master key from the replacement immobilizer (which most likely is NOT cut to work in the ignition of the Accepting vehicle) right next to the ignition switch (and its pickup coil)
(2) insert the non-chip key into the ignition.
If the gods smile, the Prius security LED will stop blinking (the chip in the key agrees with the ICU) but the car will not start (because the ICU does not match what the ECU remembers).
(3) Turn the key to the ON position, and let it stay there for at least 30 minutes. This is to allow the ECU to “learn” the ICU. Go have coffee, or whatever. Art (remember him? from Art’s Automotive?) tells a story from when he first tried this, the 12v battery died. Took him several tries to get it right. Hence the 12v battery charger back in step (2).
(4) IT’S BEEN A HALF HOUR…
(a) Take the non chip key out of the ignition
(b) Leave the old master key near the ignition switch
(c) Put the non-chip key back in the ignition switch and
(d) Move ignition key to START position.
If the car starts, SUCCESS! You now have a working (mechanical key and electronic master key) combination for your vehicle.
If it does NOT start, you have to debug what went wrong and (perhaps) repeat the ECU/ICU training process. All steps, from the beginning.
I’ve only done this once, and it worked for me first time. Whew.

ASSUMING SUCCESS:
Follow steps 11 to 3 (in decreasing number order) to put all the parts back.

Now: get additional chip key blanks cut to mechanically fit the vehicle, and
go through the key learning process.
NOTE: there are DIFFERENT learning processes for black Master keys and grey Toyota Valet keys. Apparently Toyota computers can tell the difference, and can’t make a Valet key into a Master key.
This process is documented elsewhere, but here is my shorthand version.

Key learning for new ICU:
(1) Start with: operator in driver seat, ignition off, doors closed. Old key and New key handy.
(2) Insert old master key into ignition
(3) IMMEDIATELY turn the key from “Lock” to “On”
(5x new Master key) (4x new Valet key)
End with key in “Lock” position
HINT for next step: open the door once, push the door button (n-1) times, then close the door.
(4) Immediately open and close the driver door
(6x for Master key) (5x for Valet key)
End with door closed
(5) Remove old key, then IMMEDIATELY insert new key into ignition and turn to “ON”
(HINT: Programming is going okay if the security LED is OFF and not blinking)
Leave the key in the “ON” position for at least one minute.
(6) For more than one key, remove first key after one minute, then insert next new key
and leave it in the “ON” position for at least one minute.
(7) When done, remove key from ignition, then open and close the driver door.
(8) TEST each key after you complete the process.

When you're satisfied that all your work is successful,
(29) remove the battery charger. Yours is not a fully electric Prius.

Clean yourself up. Remember, you are NOT paying Toyota something like $100 per hour to do this task. Bandage any wounds, put tools away, then celebrate appropriately.

Congrats to anyone for making it this far.
Helpful feedback for improvement is appreciated and gratefully accepted.

 

...and I only discovered this morning that I can't edit the headline for this thread. The 'got' should be 'for'...

If someone has the actual instructions for the full immobilizer/lockset replacement kit, please post a link or upload. I haven't found this procedure in my Toyota manuals (not to say it ain't there; I just ain't found it), and would like to see if there are any shortcuts or helps/hints for this procedure.

It might be easier if the steering wheel is removed (which isn't all that hard; just add a steering wheel puller to the tool list) to give more elbow room for ICU module access, but then requires steering wheel alignment realignment at re-assembly. I looked at that; decided it was too much work. I opted for speed (and minimal special tools) over comfort.

 

Chap, thanks for the correction. Yup, that's the Brake ECU under the steering column. My bad.
"Master" versus "sub" keys.... sloppy terminology on my part.
I had, for the target vehicle, exactly one Toyota grey "valet" (aka: "sub") key.
Once I established a functional "master" key with the new ICU, I tried the "master recognize" procedure with the grey key; when tested, it failed to allow the engine to start.
So I tried the "sub recognize" procedure, and it worked. The ICU recognized the grey key for engine start.
Neither key opens the trunk, but I think that's a trunk lock cylinder issue, not a key issue.
PrimusPaul, thanks for the add. My Prius keys never had a battery... I believe you're thinking of the ones that are combination key-plus-remote-entry types.
Yup, there now exist ways to "clone" keys to be electrically as well as mechanically equivalent; I didn't know if that process worked for Gen1 Prius type keys.
Since I had access to an otherwise-unemployed immobilizer-plus-master-key, this project was intended to give the target vehicle a master key capability to recognize additional keys "by the book", as opposed to just generating additional functional keys.
My working definitions:
"Valet cut" is the tooth configuration on the key that will NOT open the trunk.
"Master cut" is the tooth configuration on the key which WILL open the trunk.
"Valet sub" key will start/run the car, and NOT (open trunk OR allow new key recognition by the immobilizer).
"Master" key will start/run the car, and (open trunk, AND allow new keys to be recognized by the immobilizer).

Brian, I agree; the trunk access "feature" is a curious security strategy. Given that valet-cut key allows access to the vehicle cabin, at which point the trunk latch can be released from inside the cabin, doesn't seem particularly useful. I guess Toyota considered having a trunk lock inside the cabin, but later omitted the feature.
The "valet sub (grey key)" security utility is in the "won't allow new key recognition" feature.

Thanks to all who added to the thread.

 

Interesting, about the trunk lock 1/4 turn trick/feature... I never knew that.
PrimusPaul, on page BE-77 of my 2002 Prius repair manual (RM883U2) there is shown a diagram with a key blank having "Lock" and "Unlock" buttons... found that quite by accident. So I guess NHW11 had combination function fob/keys at one point.

Getting to the trunk from the cabin: remove the rear seat lower cushion (pull up - HARD- on the corners), 10mm socket to remove two or three screws along the lower edge to release the upper rear seat back, then lift it up; four screws to remove the two vertical seat back supports and then the black plastic vent pad, and you're there. I don't consider that really hard.

Okay... so I spent some time looking at the lock mechanism on the '03 Prius, trying to get my master key to work. I suspect the lock cylinder is frozen by corrosion... and I see a couple wires running from the end of the lock cylinder. Before I go running to the wiring diagram, can anyone enlighten me as to what they're for? I seem to remember that at one time there was an electric trunk release "easter egg" mechanism (push the unlock button 3x on the key fob, or some such), but I can't find a link.

Followup: those wires are the "Luggage compartment unlock switch" attached to the lock cylinder. All the electrical unlock add-ons require an additional solenoid to trip the unlock mechanism. I guess it's to let the driver know that someone is unlocking the trunk...