During my research with TPMS issues some users had issues with inference from things plugged into the cars 12V/USB ports too. Do you have anything plugged in like a USB dongle? As for the relearn procedure having the old set in the trunk may effect the procedure, I would highly recommend you get Tesla to do a relearn without any extra sensors in the car.Thanks. I think I know what the issue was and hopefully I will be able to resolve it. For anyone that may have switched to after market rims and experiencing TPMS issues:
Background: I swapped the OE tires/wheels with Vossen VFS-1 20 x 9 with 35 ET. No issues with TPMS sensors. I then recently swapped just the rear two tires/wheels with same type of wheels, but 20 x 10 and 32 ET and slightly larger tires 275/40 r 20, which makes them 28.7 inches in total diameter. The rear two sensors took several days to finally come on, but would sometimes drop off again and trigger the TPMS fault warning on the dash. I then went to Tesla Service Center for relearn procedure, but only 3 of 4 sensors came on. Here is what I learned caused the problems:
1. Discount Tire installed the sensors upside down, with the logo side facing the barrel of the wheel, and the epoxy side facing the tread. My sensors are installed on TPMS valve stem adapters (aka "shorties") b/c the OE valve stems are too long when installed on these Vossen rims and would have hit the calipers. The shop said they had to install the sensors upside down b/c of the angle on the valve stem was about 45 degrees and was blocked by the barrel at that angle. I was able to contact Continental, the manufacturer of the TPMS sensors. First, they said for this type of sensor, they need to be installed with the logo side facing out towards the tread, and the epoxy side facing the barrel of the rim. Second, they said the valve stems are adjustable from 15 to 40 degrees. See pic. There is no need to have the sensors at the max angle, as these are designed to fit multiple types of rims. Continental provided a link to their website with a lot of great info about their TPMS Redi-Sensor: TPMS Video Series – How-to Tech Tips - Redi-Sensor
2. When I had Tesla do the relearn, there was an old set of TPMS sensors in the trunk. The technician said it would not be a problem and went ahead and did the relearn. After the relearn procedure, he had me drive for 20 minutes but only 3 of 4 sensors came on. Based on some of the Continental videos at the above link, this is apparently a common mistake that causes problems during relearn procedures.
(Side Note: if you have sensors on an adapter like mine and you are using a TPMS device to test the sensors, you may have to place the device against the tread near the valve stem to get a good reading. You may not get a reading just from the side wall. Also, Continental said to have the device angled downward when getting a reading, as holding it horizontal may cause it to read the sensor on the opposing wheel.)
Awesome! Happy to hear its all sorted outTook the car to Tesla Service Center and had the relearn procedure done. Issue resolved. So it was a combination of 2 things: (1) Discount Tires installing the sensors upside down in the adapter, causing intermittent signal that would drop off every few days; and (2) Tesla doing the previous relearn while leaving the old set of sensors in the trunk.