Your Keys, Immobilizer, and You. What you need to know!

Go down

Your Keys, Immobilizer, and You. What you need to know! Empty Your Keys, Immobilizer, and You. What you need to know!

Post by xxfallacyxx on Wed 26 Jan 2011, 9:23 pm

The information in this thread is for learning purposes only. I, nor can be held responsible for your choices. I hope this helps at least one person. I'll start with what is in what I refer to as the good book, our owner's manual. On page 70 the section about keys begins. I will add clarifications in parenthesis where I feel necessary.

"Your car comes(This is if you bought your car brand new from the dealer) with two master keys(black) and a valet key(gray). The master key fits all the locks on your vehicle:

  • Ignition
  • Doors
  • Trunk
  • Trunk release handle
  • Rear seat trunk access
  • Glove box

The valet key works only in the ignition and door locks. You can keep the trunk, trunk release handle, rear seat trunk access and the glove box locked when you leave your car and the valet key at a parking facility.

You should have received a key number plate with your keys(Again, brand new from dealer). You will need this key number if you ever have to get a lost key replaced. Keep the plate stored in a safe place. If you need to replace a key, use only Honda-approved key blanks.

These keys contain electronic circuits that are activated by the immobilizer system. They will not work to start the engine if the circuits are damaged.

  • Protect keys from direct sunlight, high temperature, and high humidity.
  • Do not drop keys or set heavy objects on them.
  • Keep the keys away from liquids. If they get wet, dry them immediately with a soft cloth.

The keys do not contain batteries. Do not try to take them apart.

Learning key(the red key)

You should also receive a small case containing a learning key. It is used by the Honda dealer to code replacement keys to your car's immobilizer system. It must not be used in your car's ignition switch. Store the learning key with the key number plate in a safe place.

If you attempt to use the learning key to start your car's engine, it may cause a malfunction that makes your master and valet keys unusable. If this happens, you should contact your Honda dealer.

If you need a new key made, take the key number plate, the learning key, and all other keys that came with your car to your Honda dealer.

Remote Transmitter
(I'm going to skip this section)

Immobilizer System
The immobilizer system protects your car from theft. A properly coded ignition key must be used in the ignition switch for the engine to start. If an improperly coded key (or other device) is used, the engine's starting circuit will be disabled.

When you turn the ignition switch to ON(II), the immobilizer system indicator should come on for a few seconds, then go out. If the indicator starts to blink, it means the system does not recognize the coding of the key. Turn the ignition switch to LOCK(0), remove the key, reinsert it, and turn the switch to ON(II) again.

If the system repeatedly does not recognize the coding of your key, contact your Honda dealer.

This indicator will also blink several times when you turn the ignition switch from ON(II) to ACCESSORY(I) or LOCK(0).

The system may not recognize your key's coding if any other key is near the ignition switch. To make sure the system recognizes the key code, keep each key on a separate ring.

Do not attempt to alter this system(Unless you are a trained professional, know exactly what you're doing and are prepared to take care of the consequences if you mess up, or are under the direct supervision of someone who knows exactly what they are doing) or add any devices to it. Electrical problems could result that may make your car undrivable.

If you have lost your key and cannot start the engine(curious about this, what do you do if you lost your key but can start your engine?), contact your local Honda dealer."

I'm gonna stop there, following that is information on the Ignition switch positions.

The following is from the 1997-1999 Honda Prelude service manual(Helms manual, see the 5th gen resource thread for download links and other helpful write-ups), Chapter 23, page 196.

"Immobilizer System

The vehicle is equipped with an immobilizer system that will disable the vehicle unless the proper ignition key is used. This system consists of a transponder in the ignition key, a receiver, a control unit, an indicator light, and the ECM.

The vehicle has three kinds of keys.

The master(black) key is used for:

  • Ignition
  • Door lock
  • Trunk(and all other locks relating to the trunk)
  • (Glove box)

The valet(gray) key is used for:

  • Ignition
  • Door lock

The learning(red) key is for rewriting the immobilizer system. NOTE: This key cannot start the engine; do not use it except for rewriting the system. If someone tries to start the car with the learning key, all master and valet keys must be relearned.

When the key is inserted in the ignition and turned to the ON(II) position, the immobilizer control unit sends power to the transponder through the receiver. The transponder then sends a coded signal back through the receiver to the control unit. The control unit in turn signals the ECM, as well as the starter cut relay.

(Diagram in manual)

If the proper key has been used, the starter cut relay will be energized, and the ECM will energize the fuel supply system. The immobilizer indicator light(green key light on the right side of gauge cluster) will simultaneously come on for about two seconds, then go off, thereby signaling that the immobilizer unit has recognized the code sent by the transponder.

If the wrong key has been used and the code was not received or recognized by the unit, the indicator light will come on for about two seconds, then it will continue blinking until the ignition switch is turned OFF

If the ignition switch is turned OFF, the indicator light will blink for about five seconds to signal that the unit has been set correctly, then the indicator will go off.

Problems and Replacement Parts
(This chart is available in it's original form on page 198 of chapter 23)

To use this chart, please find your problem on the numbered list. Then, look below to match the problem's number to the replacement parts.

  1. Master or Valet key has been lost or addition Master or Valet key is required.
  2. All Master and Valet keys have been lost.
  3. Learning key has been lost.
  4. Immobilizer receiver does not work.
  5. Immobilizer control unit does not work.
  6. ECM does not work
  7. Ignition switch does not work.
  8. Door key cylinder has been broken.

1. Parts Set: A | PGM Tester required : Yes
2. Parts Set: Ax2, and B | PGM Tester Required : Yes
3. Parts Set: B | PGM Tester Required : Yes
4. Parts Set: C | PGM Tester Required : No
5. Parts Set: B | PGM Tester Required : Yes
6. Parts Set: E | PGM Tester Required : Yes
7. Parts Set: D | PGM Tester Required : Yes
8. Parts Set: F(G) | PGM Tester Required : No(Yes)

Part Sets

A: Blank Key
B: Immobilizer Control Unit, Master Key, Learning Key
C: Immobilizer Receiver
D: Ignition switch with immobilizer receiver, Immobilizer control unit, Master key, Learning key.
F: Door key cylinder, Master keys for doors open or locked
G: Ignition switch with immobilizer receiver, Immobilizer control unit, Master key, Learning key, Door key cylinders, Trunk key cylinders.

(With problem number 8, solution/part set F will simply replace the broken door lock cylinder with a new one, and you will receive a new key or keys for that door or doors, you will end up with more keys for your car. Solution/part set G will replace all lock cylinders, and immobilizer system with new parts, your old keys will be invalid, and you will receive a new set of keys for your car.)


  • The immobilizer system can store up to five key codes.
  • If it is necessary to rewrite the immobilizer control unit to learn a new key, the dealer needs the customer's vehicle, all it's master and valet keys, the learning key, and a PGM tester equipped with an immobilzer program card. Any key that is not learned during rewriting will not longer start the engine.
  • If the customer has lost their key, and cannot start the engine, contact Honda customer relations.

Beyond this in the manual are wiring diagrams, and testing procedures. I highly advise against attempting any of these at home. Save yourself the headache and have AAA tow your car to the dealership. Attempt any testing or diagnosis of the immobilizer system at your own risk.


Each car came from the factory with one(1) red learning key, two(2) black master keys, and one(1) gray valet key. The red learning key that came with the car is paired with the immobilizer system. The red learning key that came with your car is the only red learning key that can be used with the immobilizer system in your car.
If you lose your red learning key and your other keys, you will need a new immobilizer system. Prices vary, but this is expensive.
If you've lost any other combination of keys but retain your red key, get your car to the dealership, making sure you bring your red key and any other keys you may have left. The dealership can then make you a new key and program your immobilizer to recognize it. This is relatively cheap.

I'm aware of many people posting about alternatives to Honda's repair/replacement procedures. I personally cannot confirm these to be true, and in the same sense cannot confirm them false. It is your choice and your choice alone which route you choose to take to get your car running again. Best of luck.

The following information is courtesy of Psychoboy

the red key is not available by itself, it comes from honda tied to a unique immobilizer box (97-99 P/N 04809-S30-A02, 00-01 P/N 04809-SZ3-Q03), and it comes with a new black key.

first of all, the red key and its associated box and black key are still available from honda. the 97-99 lists for $292.72, the 00-01 lists for $285.90.

of course....the red and black keys don't know what your ignition switch looks like, so they'll still have to be cut per the key code to mechanically roll your ignition and locks.

honda also sells the red key/box/black key a couple other ways (and the keys are probably pre-cut):

97 M/T - 35100-S30-A01: red, black, box, and complete ignition switch ($472.83)
98-01 M/T - 35100-S30-A03: red, black, box, and complete ignition switch ($427.03)
97 A/T -35100-S30-A11: red, black, box, and complete ignition switch ($511.42)
98-99 A/T - 35100-S30-A12: red, black, box, and complete ignition switch ($464.17)
00-01 A/T -35100-S30-A13: red, black, box, and complete ignition switch ($464.17)

97 M/T GRAY - 06350-S30-A00ZA: red, black, gray, box, switch, and all 6 lock cylinders ($574.94)
98-01 M/T GRAY - 06350-S30-A02ZA: red, black, gray, box, switch, and all 6 lock cylinders ($555.43)
97 M/T BEIGE - 06350-S30-A00ZB: red, black, gray, box, switch, and all 6 lock cylinders ($574.94)
98-99 M/T BEIGE - 06350-S30-A01ZB: red, black, gray, box, switch, and all 6 lock cylinders ($567.17)
97 A/T GRAY - 06350-S30-A10ZA: red, black, gray, box, switch, and all 6 lock cylinders ($676.25)
98-01 A/T GRAY - 06350-S30-A12ZA: red, black, gray, box, switch, and all 6 lock cylinders ($567.17)
97 A/T BEIGE - 06350-S30-A10ZB: red, black, gray, box, switch, and all 6 lock cylinders ($676.25)
98-99 A.T BEIGE - 06350-S30-A11ZB: red, black, gray, box, switch, and all 6 lock cylinders ($552.27)

installation time would vary for all of these, so you'll have to get that quote from your local dealer.

additionally, there are such a thing as 'T5' keys. these are honda OE keys that are programmable. the stock keys are pre-programmed, and the car has to be taught to recognize them. T5 keys are able to clone existing keys. it's usually cheaper/easier to clone an existing key than it is to re-program the car. if you've lost the red key, but you have a good black key, you can get a new T5 key cloned from it. not all dealerships have this ability, not all carry the keys, some don't even know they exist.

The Meat
The Meat

Posts : 1693
Join date : 2011-01-26
Age : 32
Location : Computer Bound

Back to top Go down

Back to top

- Similar topics

Permissions in this forum:
You cannot reply to topics in this forum