Hi Everyone! I am new to this forum and this is my first post so I apologize in advance if this is a well discussed topic. I bought a 2008 Mazda 3 Hatch for my son. It's been a really good car until some transmission problems as of late. Back in May, the car started having issues that felt like the transmission was slipping while accelerating and would shift hard but not past 3rd gear. The AT and Check engine light was on so we took it into a shop. They said the code was for a bad shift solenoid but after testing all of them and finding they were good they replaced the TCM. $1,200 later we had a great running car again until this week. My son called me and said the AT and check engine light was on again but after turning it off to check things out and restarting it the AT light went out and the car drove fine. He brought it to me and I checked the code. PO758 B Solenoid. I cleared the code and he drove the car for another 3 days without issue. Yesterday on the way to work the AT and check engine light went off again and it went into limp mode. We had it towed home and after restarting it the AT light went off again and once again the code was PO758. I proceeded to pull and bench test all the solenoids. The ohms are all within specifications and they all click when hit with voltage. I am thinking TCM again but I hesitate to replace it because it's only 3 months old. It's OEM from Mazda with the E update. Is it possible this thing could be bad?

 

How clean is the ATF? What brand of ATF?

How much does B Solenoid cost? Might be a cheap option to R&R the solenoid?

The TCM should have a 12mth parts warranty.

Who fitted the TCM? Has it been programmed to the car by Mazda?