Trans failsafe with codes.

GSXRliterbikz · #1 10-23-2016, 04:05 PM

So I did some searching and found that there are several issues that the X trans is known for. Coming from an e38 background, I always thought the 5hp24 was a pretty rugged trans. All 740's from 97 up use them.
So I was a bit surprised to see so many possible issues.
Just wanted to check with everyone and see if some have had similar issues.

The codes I pulled were with inpa in the tcu. 5 codes. Pressure controller EDS 1-5.
All said open circuit or short circuit to ground.
Its a hard error, always present.
First time it happened was on the highway. Had been driving for over an hour, on a lightly rainy day.

From the research I did, my first place to look will be the connector on the back of the trans. I guess it can get dirty and short things out. But my issue is not intermittent. I left the car in the garage overnight and theres no change.

Other info on the car is its an 04/01 build 4.4 sport. New battery this week. Thought I might have a batt drain from something since my shifter light never shuts off. But since the new batt. I haven't had any issues with starting it. Alt light never comes on. Alt is a new one 6 months ago. Other than the new TFS, it runs great. Engine and trans temps seem normal.

Sponsored Links

GSXRliterbikz · #2 10-23-2016, 04:30 PM

Went out just now to look at the connector. Took it apart and cleaned it with a spray cleaner. Put it back on and started the car. Still have a failsafe, but different codes.

So maybe it is the connector and I just didn't get it clean enough?

RRPhil · #3 10-23-2016, 06:25 PM

I would just measure the resistances manually with a multimeter and see what you get.

EDS 1 should be around 5.5 - 6.0 ohms & EDS 2-5 should be between 5.5 - 6.5 ohms

The three on-off solenoids (MV 1-3) should measure around 26 to 27 ohms

Both of the speed sensors should measure around 315-325 ohms, and the temperature sensor (between pins 13 & 14) according to the graph :

I ended up making a small breakout board just to make the measurements easier

Phil

GSXRliterbikz · #4 10-23-2016, 09:13 PM

Yea, doing that while in the car will be tricky to say the least.
But I'll give it a try.

GSXRliterbikz · #5 10-24-2016, 04:25 PM

So had some time to tinker today.
I looked at trying to ohm out the pins on the round connector. But quickly dismissed it due to the royal pita that was going to be.
And since I was having errors on all pressure controllers, I had to imagine it was an electrical issue. Possibly the harness internally.
But before messing around with the pan I tried searching some more on the forum here. All I can say is the forum search engine sucks @**.
Used google to search the same words I did here and had a ton of hits. One in particular was nearly the same issue I had, only he had just 2 pressure sensor failures. Dealer replaced the trans, valve body, converter, all with no change. Turned out to be the tcu in the ebox.
I popped mine out just for giggles. Found the minutest about of green corrosion on a couple pins.
Since I have parted out many late model e38's with the same tcu, I grabbed one off the shelf, popped it in, and bingo, no more TFS. Car runs fine.

So on to why the heck water got into a covered box? Didn't see any in the bottom, no residue on the tcu case, no other signs of water in there. Is it possible that its getting in the connector on the trans and wicking up to the tcu? Its a common fault on 740's that the thermostat will go bad and wick coolant up the heater harness into the dme and pop fuses. Possible that something similar is happening here?
I took a pic, but photo buckets down right now, I'll post it up later.

jopecasa · #6 10-25-2016, 12:12 AM

Cool!

Can you please elaborate more on HW & SW?

Did you use the same variant for your E53?

GSXRliterbikz · #7 10-25-2016, 06:51 AM

Quote:

Originally Posted by jopecasa

Cool!

Can you please elaborate more on HW & SW?

Did you use the same variant for your E53?

Build months were very close. Part numbers matched, HW/SW numbers almost matched. The replacement one was from a sport package 7, so it had steptronic like the X has.
I'm sure theres coding differences that I will need to change to make it function 100%, but it got rid of my TFS.
TCU's are not vin coded like a DME. They can be interchanged as long as they are from the same era. I've done it plenty of times on 7's. When retrofitting a steptronic shifter into a car the easiest thing is to just swap TCU's instead of coding the existing one. Since the X and the 7 share the same trans, it works. I assume using an e39 one would work as well.

GSXRliterbikz · #8 10-25-2016, 06:54 AM

Heres the pic of the TCU pins. Doesn't look like much, but I guess its enough.

jopecasa · #9 10-25-2016, 07:59 AM

Quote:

Originally Posted by GSXRliterbikz

Build months were very close. Part numbers matched, HW/SW numbers almost matched. The replacement one was from a sport package 7, so it had steptronic like the X has.
I'm sure theres coding differences that I will need to change to make it function 100%, but it got rid of my TFS.
TCU's are not vin coded like a DME. They can be interchanged as long as they are from the same era. I've done it plenty of times on 7's. When retrofitting a steptronic shifter into a car the easiest thing is to just swap TCU's instead of coding the existing one. Since the X and the 7 share the same trans, it works. I assume using an e39 one would work as well.

Awesome!

Cheers for sharing info!

Sponsored Links