Only Have 1st & 3rd Gear! Help!!

[GSanchez1370]

I have a 2007 Mazda 3s automatic transmission and it has about 78,000 miles on it. The check engine light and the at light are on. I had it checked for a code and it gave me p0757. I've replaced all the solenoids. I can only go up to third gear! Has anyone else had this problem??

 

[concept]

When was the last time you had the transmission fluid changed? Was it changed when the solenoids were replaced? If the fluid had never been changed, have you checked its level exactly as written in the owner's manual? Low fluid levels will often prevent shifting, even if the solenoids are all perfectly okay.

 

[GSanchez1370]

When was the last time you had the transmission fluid changed? Was it changed when the solenoids were replaced? If the fluid had never been changed, have you checked its level exactly as written in the owner's manual? Low fluid levels will often prevent shifting, even if the solenoids are all perfectly okay.

Yes, the transmission fluid was changed when the new solenoids were replaced. Also the wiring harness was replaced as well. Could it be that it's stuck in "safe mode" and if so how do you go about resetting it? Would it be wise to have a transmission flush and have the speed sensor replaced?

 

[GrasshopperCO]

I've only had manual Mazdas, so please feel free to completely ignore my insights when it comes to how to deal with autos. If it's stuck in safe mode, can't you reset it by disconnecting the battery and resetting the ECU? I'm not trying to be pretentious by putting that in the form of a question; I'm really not sure if that'll work for your particular issue. Couldn't hurt, I suppose. Any chance you're leaking fluid? Again, I know manuals need their fluid changed less often than autos, so I'm really not sure what the procedure is here. Concept is a much better authority than I am, but I wanted to join the discussion and hopefully learn something.

 

[GSanchez1370]

I've only had manual Mazdas, so please feel free to completely ignore my insights when it comes to how to deal with autos. If it's stuck in safe mode, can't you reset it by disconnecting the battery and resetting the ECU? I'm not trying to be pretentious by putting that in the form of a question; I'm really not sure if that'll work for your particular issue. Couldn't hurt, I suppose. Any chance you're leaking fluid? Again, I know manuals need their fluid changed less often than autos, so I'm really not sure what the procedure is here. Concept is a much better authority than I am, but I wanted to join the discussion and hopefully learn something.

I appreciate your insight! I checked and no leak. Any opinions and advice is welcomed and appreciated!! New problem just arose...when shifting from park to reverse when the car is cold it doesn't go into reverse. It's like it's stuck in neutral.

 

[GrasshopperCO]

As far as I've been able to discern, a P0757 fault code translates to "Shift solenoid B stuck open", but since you've replaced the solenoids...maybe it could be the TCU/TCM? I think Mazda refers to it as the TCM (Transaxle Control Module). I'm more inclined to think it's an electrical problem with one of the control units going bad than actual mechanical issues within the transmission.

 

[GSanchez1370]

As far as I've been able to discern, a P0757 fault code translates to "Shift solenoid B stuck open", but since you've replaced the solenoids...maybe it could be the TCU/TCM? I think Mazda refers to it as the TCM (Transaxle Control Module). I'm more inclined to think it's an electrical problem with one of the control units going bad than actual mechanical issues within the transmission.

Where is the TCM located? And how much would you think to replace it?

 

[concept]

Have you seen this lengthy explaination of that code by a Mazda mechanic? I noticed that the connector (shown near the bottom of this page) can be a source of the problem. The Control Module is also mentioned.

http://www.justanswer.com/mazda/74593-mazda-3-03-mazda-transmission-no-2nd-code-p0757.html

 

[GrasshopperCO]

According to this forum post, the TCM is integrated into the ECU. I think you'd be having more problems with an ECU failure than just the transmission, so concept's link could explain it. It may well be a connector or sensor issue. Electrical problems are always a nightmare to solve :/

 

[GSanchez1370]

Then would it do any good just to replace the entire ECU?

 

[GrasshopperCO]

Then would it do any good just to replace the entire ECU?

If that's absolutely the discernible cause of the problem, then it certainly would be - your car won't ever function properly otherwise. However, I would advise strong caution: since it would be an expensive solution, I definitely wouldn't replace it on a whim. It should really only be done as a last resort, or if the problem can be traced without a shadow of doubt to the ECU.

 

[GSanchez1370]

I totally agree. I just don't know where to go from here. Soleniods and wiring harness have been changed..there's no transmission fluid leak..tried to reset ecu to get it out of fail safe mode. But I still only have 1st and 3rd gear. Anymore suggestions??