TPMS antenna repair attempt

About a year or two ago I noticed that when morning temps drop to below 50, my tire pressure monitor displays dashes for about 30-40 minutes vs usual 2-3 minutes. If there's still dashes after that time, a TPMS antenna communication error pops up. The problem disappears when it gets colder or warmer.

This time it happened again. Before throwing $300 blindly at the problem and getting a new replacement part I decided to take the module apart and see what may be wrong with it. The manifestation of the problem says it is cold solder. Feels pretty much like it is.



Well, this is the shittiest made car electronic module I've ever seen. I see no reason for MSRP $300 other than including 1000% margin in the asked price. Chinese grade plastic enclosure which is fixed to PCB with self tapping screws. The PCB is apparently hand-soldered, at least in some parts of it. It is coated with some gummy substance to protect it from moisture, oxidation and vibration. But the coating is subpar, it easily peels with a nail. Rubbing alcohol has no problem removing it to dry bone PCB in seconds. The coating is applied apparently by hands, so parts of PCB miss even that protection. I found no coating around the main chip pins that were heavily oxidized. Encircled in red.



Removed the rest of the coating from that side of the chip and reflowed the solder just to test if that was it. 3 minutes of test drive, and the tire pressures jumped in, like they used to do. That was it. I'll be pulling the module once again around weekend, wash the subpar coating off and reflow everything, now with addition of lead solder. I had to mention TPMS antenna uses lead-free solder, so large solder points like around the connector and antenna coil look like they started to disintegrate. Then I spray it with a real PCB coating and call it a day.

What the heck, Toyota?.. Is it a part of your business model? Selling crappy parts designed to fail, for insane profit. Googling for "Toyota TPMS problem" shows dozens of various forum pages where people replace this expensive module in all Toyota models. That's a very lucrative business indeed.

Eh...

 

Hmm...I wonder if I am having the same issue. My 2018 doesn't even show the PSI reading on gauge cluster. (I have a platinum model if that matters). I don't even get dashes or a blank display, I don't see anything. Where is this antenna located?

 

At the back of the cabin, above headliner. Need to pull it down and release 3-4 clips. Bolt is 10 mm.

 

I like this: https://mgchemicals.com/products/co...formal-coatings/conformal-coating-waterproof/

 

I've got 419D from them

 

The next morning it still works. The pressures popped up in 2 minutes after starting the engine.