https://techinfo.toyota.com/techInfo...pmanager/t3/ti

this is the URL for the Toyota information services

hope this helps

 

The CEL will come on if the ECU is unconnected to power and ground while the instrument cluster has power. The light is powered by the instrument cluster. the instrument cluster also has a microprocessor inside and if it doesn't detect the ECU presence by receiving certain "heartbeat" messages from it, it will turn on the CEL because it has detected a loss of communication problem.

under normal circumstances only the ECU will request the cluster to illuminate the CEL by sending a message over the CAN link. In these vehicles, the ECU is actually controlling the engine and the transmission. Toyota/Lexus has never separated these like all the other luxury carmakers have done.

 

If the ECU senses the car overheat, it's not going to start the car.

 

That's some really great info guys! This is what makes the forum great! Baldrick....are you a Lexus Tech?

 

not a tech but I design ECUs and write the software to make them work. I am a Detroiter, been doing this stuff since the 1990s.

I have owned many Toyotas but this Lexus direction is worrisome. Trying too hard to keep up with the Germans and their electronics, which hasn't helped their reliability. unfortunately its going to get worse.

 

I relayed all the info to the shop and they said Baldrick was pretty much right. They are tis yearly subscribers and have the actual tool needed for Toyota/Lexus. Problem is the tool can't connect with the ECU at all to even send the signal to the starter. They tried just for the sake of it to use a cheapo walmart code reader and no connection either. They are thinking that maybe when the alternator went out last month that something screwy might have went wrong with the ecu. They are still testing and want to have another set of eyes look at it before ordering the ecu.

 

Any luck with yours?

 

my mechanic is telling me to replace the ecu. I work for a dealer so fortunately the labor cost will be limited to a bottle of whatever he drinks. The ecu seems to be between 150 and 350 on various internet sites. Hopefully the reprogram wont be too steep.

 

if they have an electronics guy at the shop where you took the vehicle, this is what I recommend:

1) there is a fusible link box right next to the battery. they need to look in there and make sure all the funny looking links are intact. there is a thin link in there designed to pop and save all the expensive modules downstream. think of this the same as the breaker box in your basement which controls power to everything in your house. only differences are the home system breaker can be reset, and it is an AC system.

2) ecu communication problem: they need a multi-meter to check for continuity from the OBD2 connector to the battery + and - posts. OBD2 pin 16 is the battery connection and pins 4 and 5 are ground. These are the power sources for any tool.

2a) check for continuity from OBD2 pins 6 and 14 all the way back to the ECU terminals on the harness side. TIS wiring diagram should tell them which 2 ECU pins correspond to OBD.6 and OBD.14. these 2 pins are the CAN pins.

2b) If 2a passes, they need to check the resistance between OBD2 pins 6 and 14 and the OBD2 connector. it should be 60 ohms - there are 2 120 ohm resistors in parallel somewhere on the CAN link in the vehicle. if these are blown nothing will communicate with the tool. this check needs to be done with the battery terminals disconnected.

2c) reconnect the battery and let them try the tool to check faults on the VSC and the airbag computers. these are on the same CAN link as the ECU. if they can communicate with those modules but not from the ECU, then I can say you have a chance the ECU might be gone.

if 2b fails, a new ECU cannot be reprogrammed on the vehicle until the CAN bus is repaired, for obvious reasons.

an alternator failure should not cause a problem a month later. it will cause a problem right at fail time.

 

That's awesome! I agree 100% with what you said regarding them trying to keep up with the Germans. They had a niche carved out for them and they are starting to drift away from got them to where they are today. Also, it's not just Lexus but Infiniti as well. I hate leasing but I think going forward i'll look at the prospect of leasing my next car

 

Been thinking the same thing about leasing.

 

Update, the shop found a ground wire for the ecu at the fuel pressure sensor ( at least that's how I interpreted it). They were able to test the fuel pressure sensor and determine that it was bad and they believe that this is the true culprit. The part will be in tomorrow and we shall see if that resolves the issue.

 

Got my car back today. It was the fuel pressure sensor. Oh how I missed my car. Alexus is due for a detail this weekend.

 

This happened to my 07 gs350 this morning. She ran for a quick second then died. Pressing start just made the fans run and would not crank. Tried the usual jump start and jiggle the shifter, other key fob. Holy crap now I am thinking same as you guys said, ECM, security system, CAN, starter, broken wire.
Found your post (was already a member). I am suspicious because the original poster said Christmas morning his went out, mine is the day before Thanksgiving.
Found out that if you check the blue wire on either camshaft position sensor (top of each valve cover near the front - 3 wire), if you do not get a 5v sensor reference with the ign on, replace the fuel pressure sensor.
Part # : 8945830011
$340 from Lexus or $270 total shipped from parts.com I showed the lexus parts guy the $270 on my phone, and he graciously lowered his price to $330 out the door. Parts.com is 1-5 days shipping. ($40 from ebay or alibaba would not trust Chinese copy though)

I do not know how much labor they would charge.

Its located above the bell housing in the back of the motor, don't even think of seeing it without easily removing the throttle valve.

There is a recall for the fuel pressure sensor but it is only for a possible leaking gasket. They will not install a new fuel pressure sensor on this recall. I am changing it myself and will take it in for the recall after, so they can put a new gasket on and make sure it does not leak.

Thank you for originally posting this, hope fully it also helps other.

 

You should just take the new fuel pressure sensor in and tell them "Hey, I'm here for the recall and I already took the sensor out for you."