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?

 

UPDATE: Turned out to be the TCM. Had it confirmed by the shop that installed it. Surprised since it was a brand new OEM unit from Mazda. Dealer warrantied replacement and shop warrantied the labor to replace.

 

Mazda 3 AT light has been coming on for 13 months during start ups. Tranny is slipping with sluggish acceleration until fully warmed up. Hard acceleration often trips AT light. I turn off car and restart (or wait a few minutes to warm up) and problem is gone. Car is 2005 Mazda 3 S w/ 102,800 miles. Any idea? Fluid is pinkish red from siphoning and replacing. No engine light. No code reads possible. I'm in Florida, so cold start means car is off a 2 or 3 hours.