Hi,
I hope that you can help me with my problem, as my Toyota dealership here in Europe can't help me further. As you guys in the States have more experience with Lexus I hope that you have heard of such a problem allready. Please appologize for my mistakes in english in advance.
I own a Lexus GS450h 2007. Severel weeks ago after a freezing night I wanted to drive to work. The engine started and died after several seconds with the message check hybrid system and a red exclamation mark. There was no yellow check engine sign and the "ready" sign was still on. The engine fans went on. I could drive on electric power. Each time after that point I tried to start the car, the engine died immideately after starting and I wasn't able to drive the car. No ready sign appeared and allways the message check hybrid system with the reg exclamination mark and engine fans on. After that the car was towed to a toyota dealership. The car doenst't have any trouble codes in the ecu and that makes the problem complicated. They can only read the trouble codes after dissconection and connecting the battery. When the computer is attached an they try to start the car the communication between ecu and computer aborts and the message appears as above. They have no possibility to acces the ecu unless they disconnect and reconnect the battery. The dealership tried many things. They checked the sensors, some integration relay, they even tried an other ecu from an other gs450h and there is still this problem. The 12V battery was changed but that didn't help. The HV-battery was changed half a year ago as it was under warranty.
Did anybody have simmilar problems with the check hybrid system message and that the engine doesn't start but no trouble codes in the ecu.
Is there anything on the car that isn't monitored by the ecu. Any ideas are welcome and thank you very much in advance.

 

I do not have much experience but from other cars sounds like a sensor problem on the engine. My guess would be the flywheel position senzor(if it has one) or the cam shaft position sensor. I saw allot of cases on other cars, engine stalling caused by a bad sensor but they do not appear on the diagnose. I am amazed that the dealer couldn't find the solution. In this case they contact Lexus HQ and take it from there. Do you have a lexus delaer in your country?

 

Hi,

for me your suppose is right. It must be some kind of sensor that gives a wrong information to the ecu.
We have a Lexus dealer here. The Lexus dealer belongs to the same company as the toyota dealer. They are now thinking about towing the car there.
I allready contacted the Lexus HQ and they told me that the dealer must contact them for help. I will make a phone call to them on monday and tell them to contact the HQ.
I'm also amazed that the dealer can't find the solution.

 

Maybe one of the ground wires (engine block ground wire or body ground wires) is corroded or damaged

 

The dealership informed me that they now finally contacted the HQ and that they are waiting for an answer. They said that they made some snapshot data (what is that?) and sent that to te HQ aswell. Hope this will bring a solution. They also checked all cables, connections and ground connections and said that that is ok.

 

Hey warm welcome from Belgium I also have a 450h. I think I might know what this is about is. Your hybrid is a master piece of complex technology :-) one of the things specific to the hybrid is a separated cooling system for the hybrid battery. As with all fluids they have to be changed once in a while. If the fluid freezes or becomes dense / jelly you will get exactly the error you are giving in this topic :-)

 

Hi to Belgium from Germany. ;-)
I also was thinking that it could be something with the cold weather. But the car is now longer time at the dealership inside and with warm temperature in the garage. Why is the problem still there. It should have de-freezed if it was frozen. Hmm. What do you mean with jelly or dense fluid?

 

coolant becomes thicker after years of heating and cooling it becomes brown and just needs to be replaced. Many dealers do it correct however some are not very experienced with the hybrid system and replace the regular coolant but not the hybrid one. Due to this the hybrid coolant pump can fail, this does not give a error code in the ECU and there is a good reason for that. The ECU contains all info on the petrol engine. Some meters are recuperated (hybride power is for example shown in the OBD2 as boost/vacuum just like a turbo) however the hybrid parts are not all monitored that is why there is the hybrid system warning separated from the fuel powered part. So I would look into that direction. If the pump sometimes fails or is blocked the system doesn't start due to a few starts it might get unblocked and run

 

Thanks for the explain and it is quit logic. I will look at it anyway. But today I got a info from the dealership that they found the mistake, actually two mistakes.
There was one mistake with a ground connection in the fuse box. After they fixed that now the ecu has also a dtc and they can read the ecu. It says that the fuel pressure sensor is bad. They also checked the sensor and it is really bad. Now the sensor has to be replaced and I hope that the car will run soon on the street.

 

I have the exact same problem. I am on the 4th mechanic...

Let me know if that fixed your problem.

 

I finally figured it out. After going through four mechanics; two of which had it for 30 days. I decided to trouble shoot it myself. I sprayed some throttle body cleaner directly into the manifold via a vacuum line. THE ENGINE STARTED RIGHT UP... So what i surmised was that created a vacuum in the gas line. So, that means the gas pump is faulty. Oh-yeah... I ordered one from Ebay.

 

Hi Nepo... Did this fix your car? I have the same problem!