norseman76

Hey guys,

I just bought my first Lexus a week or so ago - a 1997 LS400 with 165000 miles on it and full service history. Everything works, and it drives great. The only thing is that it did not come with a remote keyless keyfob, and I'd very much like to get one.

So naturally, I searched Google and found numerous posts on here about keyfobs and programming. I got one off of Ebay, and when it landed in my mailbox this afternoon I went out to see if I could make it work. I couldn't. I was able to access programming mode, but I could not make the fob talk to the car, so to speak. Then I went in again and tried to figure out why. First, I thought maybe it could be the wrong FCC ID #, and thought about buying another fob on Ebay, but then I found this forum's FAQ, which said,

"Quote: '97 Lexus LS400 only

This system is based on the Texas Instruments fixed code transponder. The onboard computer cannot be programmed without a working pre-programmed transponder key. Duplicate keys can be programmed into the system as long as there is at least one working pre-programmed key available. (...)"

Am I to understand that the 1997 model year had a special keyless system that makes it impossible for me to get a keyfob for my Lexus the easy way? I have two keys for the car, but none of them have any buttons or anything on them, and so I assume I do not have a pre-programmed transponder key for it.

Or is the fact that I was able to access programming mode by playing with the key, door and lock button the way it is described in the general programming guides a sign that I may not have this "1997 only" system after all? And that I simply need a key with the other FCC ID #? The car is a German import, if that means anything (I am in Norway).

If anyone can tell me how I need to progress based on the info above, I'd be a very happy camper!

Have a good one,
Jan.

Yamae

There are different factors.
The radio frequency for the remote varies in countries in accordance with the regulations.
Or other than the key itself, the receiver side might have some problem.
Or don't you have any problem locking or unlocking the door when repeated many times? If it becomes slower as you repeat lock and unlock, you can't keyfob. This is often caused by the Positor in the motor or the motor itself. The motor I mean here is located in the actuator.

norseman76

This sounds ominous.

At least I didn't have any problems with the locking/unlocking speed.

Yamae

Then your door actuators may be OK.

Governments allocate and license the use of the radio frequencies and place limits on power output, so you can't expect that the German market car uses the same frequencies with the USDM licensed by the FCC.

Attached below is the RF signal for one of JDM cars I own. The centre frequency is a little below 312.3MHz. Many JDM cars use the frequency around this range. On the other hand, USDMs use the frequency higher than 315MHz. Sorry that I don't know much about the frequency allocations in Germany. Probably it is allocated in accordance with The CEPT (The European Conference of Postal and Telecommunications Administrations), I assume.

norseman76

Thanks for this info. Doesn't sound too promising, though.... I suppose I'll need to contact Lexus/Toyota here in Norway.

plexus914

You are right with having the wrong keyless fob!

FCC ID: HYQWDT-C is for USA + Canada only = 314.4MHz



UK and Europe conforms to MPT 1340 specification = 433.72MHz to 434.12MHz

The fob's back should read MPT1340 / W.T. Licence Exempt / 1512F-D Denso Corporation. I hope I was able to help...;o)...

norseman76

Excellent! Thanks for your help there, I found one on British Ebay with the right specifications.... and bought it! Fingers crossed....

norseman76

It worked!!! Plexus914, thank you very much for your help!

hotdawwg

Congrats!!!

dicer

Nice frequency domain picture. Is that your spectrum analyzer Yamae?

Yamae

Yes, it's one of my tools. It's quite convenient for me to use it to analyse problems related to electro-magnetic waves. Modern cars use different frequencies / pulses and I'd say it's almost a must to have it. Without it, I'd need some extra time to solve problems that are requested by local shop owners very often these days.

You even can use it to analyse the engine. For an example, using a tiny loop antenna and without touching injector lines, you can pick up the energy radiated from them. This makes it possible to find out quickly which injector is not working properly.