Transmission Computer Question

[RT4me]

Hey all.

Does the Trans computer throw out any codes on the OBD-II scanner when they go bad or are they tested separately (or just swapped out to test like mentioned in the manual)?

The reason why I ask is:

The Trans has be doing the 2-3 "slight slip" like most of them do (100K miles) and like my last few cars, I knew the trans would soon be on it's way out. It's had a new end clutch and some other work over the years and has been serviced pretty regular. This weekend it finally made a large clunk when I was decelerating and then was slipping. It seems to be in Limp home mode and running in 3rd gear.

It's my wifes daily driver and she's managed to milk this trans for an extra year or so. If it were mine, I'm sure it would have quit long ago the way I drive. (or did drive in my younger days).

I didn't want to chance it so I pulled over and went home and got the trailer. The fluid (which I check every week to keep an eye on it since it's on it's last leg isn't really burnt. It is a tiny bit red vs pink but not too bad considering the car has 112K on it.

I guess my question is: If the computer goes into limp home mode (if the computer is bad and not from a transmission problem), I'm guessing it would'nt burn up the fluid correct?

Given that I've owned 3 autos and the symptom is almost identical, I'm getting the trans rebuilt but I just want to make sure I don't put a good trans in with a bad computer. I guess I would know immediately when it starts out in 3rd gear!.

The car is the 1998 3KGT SL with 100K on the clock. I'm more than capable of doing the work, I'm just a little un-educated when it comes to the transmission computers on these cars.. You hear so many horror stories. I'm guessing when the trans computers go bad, they normally don't burn the crap out of the fluid?? or am I wrong?

[jpyounis1]

i def hear you. wouldnt want to start a rebuild if its just the computer..

well, did u take the TCU out?, if not id take it out. its under the center console by the accelerator pedal if you didnt know. behind the ECU.
remove the top, check for leaking capacitors, and if it smells like fish its toast. Since you have a 98, im not thinking this will be the case, but its a easy one to rule out...another thing too, check the 2 connectors in the engine bay, right on top of the the transmission. make sure the wires and all the connectors are still intact. corrosion or a loose wire can cause a problem similar to this with the pulse generators.

in the past when ive done work on auto trans at my shop, sometimes its very possible for a fried TCU to cause issues like this, as the oil pump may not be pressurizing properly, or the TCU isnt sending the correct impulses to the tranny solenoids. etc. but id rule the tcu out of the equation with ur symptoms unless the caps are leaking.

I believe you need the mitsubishi MUT-II scanner to view the trans codes. but im not sure. maybe someone can chime in.

in this case man, im going with worn clutch packs. the bad clunk was probably a loss in fluid pressure, which put the clutch packs into stress enough that the trans kicked it self into safe mode.

IPT is your best friend for our auto's. give em a call. their shift kit may be of interest for u too. good luck

[RT4me]

Thanks,

I'm out there now pulling the TCU and checking connections.

Ya' know it's funny.

It was late the other night when I checked the fluid and it looked dark to me. I was just out at the car and the fluid (while a darker red, not real pink like after a flush), doesn't really look to bad. And it does not smell that burnt.

Granted, it's not "ultra clean" but the trans does have a 2-3 slight slip and it's got 100K. I see now that I have a jerk with shifting from Park to Reverse but Neutral to Drive is fine. It's in 3rd gear which I'm guessing is the limp home mode.

The jerk makes me thing something internal and I certainly don't have a problem putting a rebuilt trans in. (Ps. I called IPT last week. I'm in PA so that works out great).

Can the trans computer give me that "Bang" into Reverse??? Now I"m second guessing just a bit. No codes on the OBD-II scanner but like you said, I think you need a different factory tool to scan the Trans Computer.

Any other input from anybody.??

[jpyounis1]

Thanks,

I'm out there now pulling the TCU and checking connections.

Ya' know it's funny.

It was late the other night when I checked the fluid and it looked dark to me. I was just out at the car and the fluid (while a darker red, not real pink like after a flush), doesn't really look to bad. And it does not smell that burnt.

Granted, it's not "ultra clean" but the trans does have a 2-3 slight slip and it's got 100K. I see now that I have a jerk with shifting from Park to Reverse but Neutral to Drive is fine. It's in 3rd gear which I'm guessing is the limp home mode.

The jerk makes me thing something internal and I certainly don't have a problem putting a rebuilt trans in. (Ps. I called IPT last week. I'm in PA so that works out great).

Can the trans computer give me that "Bang" into Reverse??? Now I"m second guessing just a bit. No codes on the OBD-II scanner but like you said, I think you need a different factory tool to scan the Trans Computer.

Any other input from anybody.??

with regards to the color, yea there was probably filings from the clutch packs in the oil causing the color, and now that the car sat, the magnets on the oil pan picked them up so the surface color is back to red.

well thats good with regards to ipt. you wont be sorry. a light move in teh trans when shifting from park to reverse is normal depending on how the car is parked etc. like on a incline or whatever.

to be honest, id drain and flush the fluid..and see what happens. its possible that might help.