Have a 2008 LS 460 that wouldn't start (car has been sitting a bit and not often used). Click start button and got nothing. No click, etc.. Got a new battery and same issue. Even had the new battery rechecked and tried another battery I had laying around. If I manually jump the st relay the starter runs fine. When I step on the brake the start light goes from orange to green. Have tried to wiggle the shifter just in case it was a neutral issue. Also tried the reset procedure with keeping the key fobs away from the car and arming, etc...

The car has a "Check VSC System" message on the dash. Had a friend hook it to techstream and he could read several modules, but Engine module always gave an U0100 Lost Communication with ECM/PCM "A". We also noticed something we have only reproduced 2 times. We left the battery off the vehicle to charge the battery or run other test. After the car set disconnected for a couple of days we could reconnect and hit the start button and the car would start and run for 1 second and then die. We have only reproduced this twice over a couple of weeks. You only get the starting action 1 time and after that it won't do anything.

Also if you hook a standard ODBii scanner it will not connect to the car although techstream works fine. I was thinking maybe this is a 5 volt issue of some sort. Thoughts?

Any help would be appreciated.

Al

 

I'm having the exact same issue you had with your 2008 Lexus LS 460, no start, U0100 code lost communication with ECM/PCM "A". Did you ever get the issue resolved?

Thank you in advance.
Roger

 

Try closing an locking all doors,trunk,hood... arm the oem alarm.. (keeping all fobs at least 15 ft from the car) then wait 30secs.. unlock the car get in an attempt the start again.. once running leave running for 5 mins for the cpu to reset.

reposted from this thread. https://www.clublexus.com/forums/ls-...w-battery.html

 

I'm experiencing the same thing, haw did you resolve your issue? Thanks

 

I'm running into a similar issue/symptom - however, given the car isn't recognizing the key fob, I don't know how to arm the oem alarm. I've been trying to use the mechanical key in the driver door to arm the alarm, but it's not working. I did all of the other steps, but didn't solve the issue. Any advice?

 

Does your instrument cluster light up ?

 

Yes, the instrument panel is active. I should have clarified - I can start the car by holding the key fob next to the ignition button, then starting the car. The car starts fine, etc. However, it still won't recognize the key fob to lock/unlock the doors, open trunk, set off alarm, etc. I have to use the mechanical key again to lock/unlock. I've tried with both key fobs I have - both have new batteries in the fob itself and we both working perfectly until I disconnected the car battery before checking some fuses for a separate issue with the headunit/center console removal. Could that be related?

 

So, with the wireless remote key in your pocket, while you are sitting in the driver’s seat, observe the start button while you depress the brake pedal. You should see a green light in the START button when the brake pedal is depressed.

 

bring both keys into the car put them in the cup holder , press the power button once, wait then once again then let it sit for a few minutes, then press the brake and start you are sure the car battery is sufficient ? Carcarenut was saying something about it today on one episode about something similar

 

I'm having the same problem did you resolve issue

 

If anyone is having this following symptoms (2009 LS460):

Nothing happens when start button is pressed.
Electric fans come on when key/button is in acc position.
Check VSC system on dash
Cannot communicate with ECU.
Techstream shows U0100
Sometimes the car will actually crank (but not start) after is has been idle for some time.

What I found as the problem:
Fuel pressure sensor

The fuel pressure sensor is faulty and is pulling down the 5 volt supply to the ECU, which causes all kinds of havoc.

The fuel pressure sensor is located under the intake manifold. It is quite a job to get to and replace.

 

My 2008 LS 460 had been sitting a while and the batteries charge was depleted from a windshield camera I didn’t turn off. I took it back to NAPA for recharge and the battery checked good and charged 100%. When I try to start it, it will turn over a time or two without starting. Everything still comes on and lights up and the start button turns green when foot placed on the brake, but the engine doesn’t try to start when pushed. If the battery is disconnected a few minutes it does the same thing all over again the same exact way. I’ve attached the battery, used the fob to lock and unlock doors, open close trunk and closed hood. I also set off OEM alarm and turn it off with fob. Nothing seems to work. Any suggestions would be so much appreciated. Thank you.

 

I think your battery is a “goner.”

 

The batteries only about 5 months old. It’s an AGM battery that’s why I took it back to NAPA for them to recharge it since it was a NAPA battery. They charged it overnight on a slow charge to 100% checked it and it checked OK. I thought it might be something to do with some kind of security system. All it has is the OEM system.

 

Sounds like you’re doing the right things. Check your connections.