2023 Ranger Lariat. Almost to VA from FL the "Check Brake System" and brake light popped on. Brakes work fine. Took it to the dealer and, after 2 weeks in the shop, they decided to replace the booster. That didn't fix the problem. It appears to happen only when cold (<40) after roughly 30 minutes of driving. My dealer is stumped. Any ideas?

 

For starters, a capable scan tool will be required without which you could spend a lot of $$$ and still not find the cause.
Because it is under warranty , I would request the use of a loaner until they fix it.

 

I've been told that the computer is not recording any errors, so the scanner is of limited value. It appears to be caused by something not happening that should, rather than something happening that shouldn't. A loaner would help, but this truck is equipped to be towed behind an RV, and I need to get back to Florida. I guess I could ask for loaner and have them bring it to Florida when it's fixed...how far would that request go?

 

When you said. "Your Dealer", thought you were close to home.

A capable scan tool can tell you a lot .
If you know what is supposed to happen and it isn't , if you know what to look for the scan tool is the answer. There is no other way to see what is or is not happening on today's vehicles. The ideal situation is to be able to produce the problem so when repaired that set of conditions is repeated or we would not know if the problem was corrected. If the person doing the checking is on a flat rate basis and warranty only pays so much, get the picture?
System codes do not contain the solution to a problem ONLY direction on where to start checking.
If the problem is intermittent and in this case below a particular ambient temperature, those conditions need to be considered also.

 

I did make it home, outside Richmond, Va. The dealer says that they've got the "computer" hooked up, but now the error doesn't happen. I'm trying to escalate through Ford, Inc. There are only so many causes for that error message, so Ford engineering should be able to work backwards to identify potential issues. I'm also taking your advice to ask for a loaner.

 

Glad you made it home safely.
Threre is a tool very similar to a flight recorder that gets connected to the vehicle and it records all necessary info .A good tech,if he/she has the tool will examine the inputs to the vehicle computer and the time it takes place. With that info, the tech can pinpoint the problem area and determine what is or is not happening.They are supposed to know what is supposed to be taking place.

Unfortunately, not everybody has the tool or maybe wants to get involved with it.

Dealership service departments have access to the info and usually have the tools to do whatever repairs might be required. Outside shops have to pay for a subscription to gain access to that info. The problem is to find a shop with a person willing to tackle the problem. Warranty work sometimes ,,,,,,,,,,,,,,,,,,,doesn't pay that well.

If possible, can you kinda note, what you, and the vehicle, are doing at the time the notice shows up? That info alone can be very helpful.

A little side note, the engineers cannot always anticipate some unusual situations that take place out in the field.