2002 Acura MDX Q&A
2002 Acura MDX Question: Did my transmission really need to be replcace?
Hi. Last summer, my check engine indicator lit up and I took it to the dealership. They found Code P0740. They noted on my receipt that they found the transmission to be failing and recommended it to be replaced. I didn't notice anything wrong in the way my car was running. No noises, goes into reverse when I put it on reverse, wasn't slipping, it was running great, actually. But I know nothing about cars and when I was told that my transmission needed replacing, I had it replaced. Looking at my receipt, it appears that they also changed the ECU. The diagnosis costed me $70.04, and the transmission and ECU, $5,421.90. (Please don't scream). I was just talking to my friend about it and he told me that the only possible affected components with that code are 1) hydraulic control system; 2) torque converter, and 3) transaxle. He also said that failure of any of these three components would render the car undriveable. But my car was running just fine. He also said that the transmission is irrelevant, and the ECU is irrelevant. Can a mechanic please confirm all that? Thanks guys! - applewarren
P0740 indicates that the contorller detected a malfunction in the torque converter clutch circuit. This does not indicate a hydraulic problem, rather an electrical problem. In order to diagnose the TCC system one would have to check out the TCC control solenoid which is in the valve body in the transmission, so some minor disassembly of the valve body would have been in order as well as checking other parts of the electrical system. It's possible for a simple problem to cause that code or there could be complications. It'd be interesting to hear how they diagnosed the P0740 code. it's possible that the entire system failed requiring a new controller ant complete transaxle but I don't think it's likely that there wouldn't be other symptoms of a failing transmission and controller. You say the car drove well, I believe you but if you had a code P0740, all it would do is not go into torque converter clutch (TCC) lockup, which you might not even notice if youre're not hip to cars especially. I don't know what your friend is trying to tell you about the ecu being irrelevant or the trans being irrelevant. I think you needed a second opinion from an independent Acura specialist or a transmission shop. There's no telling what was actually wrong at this time because the trans and ecu went back to the factory or rebuilders and the evidence is gone. Here's a directory link for you if you want to find other shops: http://repairpal.com/directory?address=98029&car_brand_names=Acura - Superbob
There are several steps required to properly diagnose code P0740 on your MDX. The first step is to verify that the line pressure is good (which it probably is if it drives and shifts ok). If ok then check TCC and pressure control solenoid valve C for proper operation. If those are ok then remove transmission and inspect o-ring for torque converter, if that is ok then the converter and transmission most likely need to be replaced. One of the problems with the design of these transmissions is that the transmission needs to be removed and disassembled to change the filter. It is very important to change the fluid at least every 50k miles to ensure longevity. Always use the proper fluid (this transmission uses Honda ATF Z1). It is impossible to say at this point what exactly was wrong with your transmission. I will say that if the converter clutch was slipping, then the fluid was probably contaminated with clutch material which will eventually clog the filter screen and lead to other internal mechanical problems. The ECU does not normally get replaced when overhauling the transmission unless it has a problem driving the solenoids (which should be diagnosed before removing the transmission). In general, a dealer is not the most economical place to have transmission work done. If internal problems exist, they will replace the entire transmission rather that overhaul or repair it. James - Jamesw