lexusride1

Hi guys,

I'm having issues with my Lexus IS350 2015 F sport and I'm really stuck at this point, so the car had an issue with one of the flaps on the HVAC unit being faulty, so I made the decision to replace the whole unit, I disconnected the battery and started removing the dashboard and disconnecting everything, took out the entire dashboard bar and replaced the HVAC unit and proceeded to install everything back again, once everything was reconnected and reinstalled, I plug the battery and attempt to start the car but it only cranks and doesn't start up, I've triple checked all the wiring and connectors and everything is connected, I even went back and took the dashboard out again just to check if I've missed something but everything was connected. I did connect the scanner and the following codes were showing:

- U0327 - Software Incompatibility With Vehicle Security Control Module
- B2620 - ECU Power Source Circuit

Note: the car was running fine before the removal of the dashboard, and the timeframe of the whole process took around 2 - 3 days, so the car was left with battery unplugged over the course of 2 nights or so.

Any insight on helping rectify this issue would be greatly appreciated. Thanks.

jmatc

Interesting. Did you touch the sunroof control panel by any chance? Check those connections as well just incase.

What were you trying to accomplish initially by removing the dash?

Farina300

B2620 ECU Power relates to the Multiplex Tilt and Telescopic ECU for the steering column - There's a possibility of a pinched/broken power wire here as it obviously states "power" in the code so check to see if you're getting 12 volts to the steering ECU (code sets if less than 8 volts for more than 10 seconds).

U0327, per my resources, states "The Main Body ECU doesn't receive data from the Certification ECU for over 10 seconds" and is a CAN Communication related issue - The Certification ECU is also known as the Smart Key ECU and relates directly to the smart key function, located behind the glove box. I *believe* what is happening is perhaps again a wire got pinched in this whole process, or the smart key ECU for some reason lost all programming of the smart key itself, and is no longer sending a "this is a known good key to this specific vehicle" signal to the ECU to allow the vehicle to start. So it just cranks as if the key is programmed just enough to send the signal to detect that a key is in the vicinity, however doesn't recognize it therefore doesn't start. I know you stated you had removed the dash a couple of times to ensure you got everything plugged in, but it doesn't fully rule out a broken wire. Ultimately this may end up causing a trip to the dealership to possibly reprogram the key to the car, or I believe a lot of mobile key programmers can come to you for it. Given the code states software incompatibility, I would assume the car just lost the key programming.

The diagnosis of communication issues can be lengthy, but the easier way to see if the CAN lines are in good condition is to remove the battery negative terminal, place a multimeter on the diagnostics port pin 6 and 14, and set it to ohms and see what the reading is. With all CAN communication in good condition, it will show 60 ohm. If one of the resistors is missing in any of the communication, it'll either show 120 ohm, or some other very weird number, and if the CAN lines are shorted together it'll simply show zero ohms. At least this way if it does come back with a 60 ohm reading, you know everything is hooked up correctly, and you can suspect the car just lost the key programming. If it's anything else, you have to chase wires.

EDIT: and as always, check fuses before diving really deep

-Shane

lexusride1

Turns out the car didn't like me replacing the HVAC, so I swapped out the modules on the HVAC with the original ones and it fixed the issue. Maybe some type of programming is required module replacement is required?

PSGT4

Lexus has a freebie recall to replace these as a “one-time” fix for this issue. The flap thing is literally the only issue my 2015 is350 has ever had.