1G Transmission Starts in 3rd?!?

[dsmboise]

Just got this thing running, but not driving!

It seems that the transmission is starting out in a higher gear or something.

Has anyone ever experienced this or heard of this problem?

Thanks!

 

[DSM1G90]

Sounds like an automatic.

Some one has worked on it and put the tranny in 'limp' mode when the two big wire 16 wire harnesses are connected with the wrong respective connectors that goes to the tranny.
.
Check and follow wire color codes to see if the colors match per each end of the two connectors.

 

[dsmboise]

Awesome! Thanks! I will try that.

Yes, it is an automatic. a KM175, I believe.

The someone who has worked on it is me, but when I tore it down it was soon evident that someone else had been in there not too many miles ago. I got this Talon in a "buy one for $500, get that piece in the back for free!" sale at a local thrift shop slash car dealer (Youth Ranch!).

I just might have hooked up the wrong harnesses. After reading about the manual shift control the other member is building, I started to figure it out: if both switches are off, it is in third. I thought: "wow! that must mean that I have no voltage to the first two solenoids."

Thanks again. I'll keep you posted (pun intended) on my progress

Oh, Wait!

Do you mean at the TCU itself, or at the Trans?

I am not sure if I have located the TCU or not. I found a 3 harness control unit under the carpet, under the ECU.

Do you think that is the TCU?

 

[Bud92gsx]

Auto magic..

Your tcu is probably shot..You should still have 1 and 2 manual gears..But put in drive and its stuck in 3rd(limp mode).

Swap out the tcu, you should be good to go..

The tcu is behind the ecu closet to the firewall behind radio etc..It sits horizontal, the ecu sits vertical

 

[Kapok6]

Sounds like an automatic.

Some one has worked on it and put the tranny in 'limp' mode when the two big wire 16 wire harnesses are connected with the wrong respective connectors that goes to the tranny.
.
Check and follow wire color codes to see if the colors match per each end of the two connectors.

+1

Myself and a good friend of mine both experienced this. There are two connectors beside each other for the trans (in the engine bay) that are the same design. (No idea why mitsu would use the same plugs so close together).

I was ready to pull the trans back out and so was my buddy. I ended up realizing the wire colors didn't match, so I disconnected them, reconnected the plugs to match the wire colors, and bam, everything works fine.

I told my friend to check this before he did anything else, and sure enough, he had gotten the connectors mixed up too. He switched them around, and trans operated fine.

 

[daplatano91]

Make sure the two four pin connector for the transmission are not swapped. One should have three wires yellow orange blue and go to the connector with same color wires coming from of the front of the transmission. The other should be going to the sensor to the side of the transmission under the transmission mount. Also if you can put the car on four jack stands start it an leave in in 1st gear grab your test light an probe the orange and yellow wires to make sure they both have power. then 2nd and only 1 should have power.

 

[blackrosenova40]

Auto magic..

Your tcu is probably shot..You should still have 1 and 2 manual gears..But put in drive and its stuck in 3rd(limp mode).

Swap out the tcu, you should be good to go..

The tcu is behind the ecu closet to the firewall behind radio etc..It sits horizontal, the ecu sits vertical

Do you have some kind of fetish with "faulty tcu's?"

Didnt you learn from the last situation a 3rd gear default situation doesnt automatically mean you have a faulty tcu, in fact its the least likely because most tcu codes and lack of tcu power will have a 3rd gear default.

 

[dsmboise]

Thanks Guys!

The harness that is going to the solenoid group (at the front of the tranny) right now is a green, red, black, white.

The harness that connects to the sensors (inhibitor switches, I think) is red, blue, orange, yellow. but THAT connects to the sensor harness and it has four GREEN wires! Thanks Mitsu, way to keep it confusing!


I think you guys are right though: fried TCU. The ECU was bad, why break a trend?

I'm going to try for voltage at the solenoids. Just to HOPE that I don't have to buy a TCU - they look EXPENSIVE!

Sorry to be all gushy about the thanks and all, but I am SO not used to people who KNOW what they're doing, trying to help me with this car. So please be patient with my gratitude!

Make sure the two four pin connector for the transmission are not swapped. One should have three wires yellow orange blue and go to the connector with same color wires coming from of the front of the transmission. The other should be going to the sensor to the side of the transmission under the transmission mount. Also if you can put the car on four jack stands start it an leave in in 1st gear grab your test light an probe the orange and yellow wires to make sure they both have power. then 2nd and only 1 should have power.

I'm going to do that right now.

 

[Bud92gsx]

Fetish no..But most of the time its a faulty tcu or fuse..

Now if your done calling my bluff we can get back on topic.I didnt write tech article on bypassing the tcu to get backlash from you..

 

[blackrosenova40]

Fetish no..But most of the time its a faulty tcu or fuse..

Now if your done calling my bluff we can get back on topic.I didnt write tech article on bypassing the tcu to get backlash from you..

Sorry but a real diagnosis in this situation would go like this...

1. Check for TCU codes, no codes move to step 2, otherwise step 3.
2. Verify TCU is receiving proper igntion power, 12v constants, and grounds, if it isnt, then repair, otherwise replace/swap tcu and recheck.
3. Diagnose and repair for related codes.

Without following steps like this your just taking a shot in the dark.

 

[dsmboise]

Umm...

How do I check for TCU codes?

Is it the same way I check for ECU codes?

I heard that the TCU codes disappear as soon as key-off happens...is that true?

 

[dsmboise]

Here's the thing:

I have it up on jack stands and:

NO manual 1st OR 2nd

NO voltage to ANY wire in solenoid connector

Which wire do I check for TCU voltage?

Is there a fusible link or fuse?

There is a missing relay in the fuse panel: top left, near kick panel. The cover says that it is anti-theft, but maybe it's TCU power?

Please help! I'm so close!

Any wiring diagrams that would designate harness assignments would be VERY appreciated.

UPDATE:

I checked for TCU codes at the DIAG harness by the fuse block.

I get a constant 5V whenever the key is on.

Pretty sure that means the TCU is shot. I will try to diagnose by replacement, but I don't know how to find a known good one under $400.00!

Also, that doesn't seem to me to explain why I don't get 1st or 2nd manually. I thought the manual valve would FORCE the transaxle into low gear. Maybe not on this KM 175.

That's all for now.

Thanks!

I think that a constant 5V at the diag terminal is like a flat line. Beeeeeeeeeeeeeeeeeeeeep. Dead, you know?

So I pulled the TCU, and opened the case. GUESS WHAT?!?! 47uf cap was blown and leaking all over that beautiful board.

Looks like it cooked the circuit trace that provides power to/from that cap.

So I pulled it, cleaned the area, fluxed the damaged circuit trace, and tinned the damaged trace.

I just so happen to have some caps from the ECU fiasco one last 47uf. So, I soldered it in and we'll see if I just might have caught the damage in time.

 

[DSM1G90]

At least you know how to repair your own blown traces and work an iron - good for you on that part!

Actually, the KM-175 is also listed at the F4A22-1 tranny and I know there are a few of them out at 'the Jungle'.

Bet you can find a TCU out at "the Jungle' for cheap, or Barger-Mattson there in Meridian or Dillons .. at least, "the Jungle"and "Pick-a-part" will let you pull your own parts.

Good luck - DSM

 

[dsmboise]

Thanks!

It ROCKS to know there are other DSMers here in the valley.

I appreciate the help!