My 99 Ls400 Won't Start. Possible Immobiliser Problem?

[soleil14]

Hello,

I bought a 1999 Lexus LS400 1 and a haft year ago. It was very reliable and I never had a problem with it.

I got a problem with the wiper control. I replaced the MPX body control to fix the problem. After that my remote key stop working. I ignored the problem and keep using the car. Two days ago, a technician reprogram my remote key and make it work again. (doors, trunk, locks, all worked perfectly). I started my car and was very happy to drive home. In the evening, when I got in the car, the car cranked but didn't start.

Is there any chance that the immobiliser system is causing problem?

When I put the key in, the security light turns off as usual.

I checked all relays and the battery and all work well. Except for the fuel pump relay that not powered when my key is in postion On. But I think this is normal.

I suspect that immobiliser system or my ECM is causing problem because my car worked very well before my remote key is reprogammed. I don't know what to do now. I live in Vietnam and it's hard to find a mechanic to fix my LS400.

I intend to replace a new ECM + key and I found this link on ebay:

http://www.ebay.com/itm/191737878103

However, I also found that there are variuos part number of the ECM for the North American market:

Model after 98
89661-50430, 07/1997-10/1997
89661-50431, 10/1997-11/1997
89661-50433, 11/1997-02/1998
89661-50434, 02/1998-08/1998
89661-50480, 07/1997-10/1997 USA TAIWAN SPEC
89661-50481, 10/1997-11/1997 USA TAIWAN SPEC
89661-50483, 11/1997-02/1998 USA TAIWAN SPEC
89661-50484, 02/1998-08/1998 USA TAIWAN SPEC
89661-50501, 08/1998-05/1999
89661-50502, 05/1999-08/1999
89661-50511, 08/1998-05/1999 USA TAIWAN SPEC
89661-50512, 05/1999-08/1999 USA TAIWAN SPEC
89661-50530, 08/1999-11/1999
89661-50531, 11/1999-08/2000
89661-50540, 08/1999-08/2000 USA TAIWAN SPEC

I haven't check what is the part number of my ECM .IKindly let me know whether the ECM part number 89661-50531 can replace the ECM part number 89661-50502 or not?

Many thanks!

[VBdenny]

If your key was reprogrammed just before, I'd start there. The computer must recognize the chip in the key which it apparently, is not doing.

[landar]

I believe the theft deterrent immobilizer would keep the starter motor from cranking but you say yours does continue to crank. So, even though it seems related, it may be purely coincidental.

I would not think that reprogramming the key FOB would cause a no start condition.

Does the FOB continue to lock and unlock the car or has that also failed? If it does still work, it is probably not the immobilizer. If it does not work anymore, it could be the immobilizer. Do you have another spare key to try? Maybe even a valet key? See what that does.