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View Full Version : 97 AT->MT swap, ECU question



Hocrest
10-03-2008, 08:28 PM
I did the MT swap on my 97 Legacy today. Everything went good and it runs great. But the mileage seems to have dropped alot. On an hour drive tonight I averaged about 15mpg.

For wiring all I've done is to splice the wires for the starter, and wire in the reverse light switch. I checked Josh's write up for Gen 1 Legs, and it says to cut pin 20 on the ECU connector. According to the FSM's for 97, pin 20 of the ECU harness goes to the TPS and the CTS, so I doubt that's the one I want to cut.

I also now have the ABS light on. The FSM's show an input to the ABS computer from the TCU. Any idea if I need to ground this or supply a voltage?

AussieDan
10-03-2008, 09:52 PM
Do you still have the TCU plugged in? From memory the auto ABS is tied in to the TCU so you'll need to keep it if you want functioning ABS.

I do happen to have a spare manual ABS controller and actuator if you want to convert those over too.

Which FSM are you using? The 97s are quite different from 98+ in the ABS department, let me know if you need a 97 fsm.

Hocrest
10-04-2008, 12:50 AM
I have the TCU unplugged. I can plug that back in to take care of the ABS.
I'm more concerned with the ECU though, it seems like it's running very rich...

AussieDan
10-04-2008, 09:25 AM
Not sure why it would be running so rich, possible your front O2 sensor is on the way out.

I took a quick look at the 97 FSM and don't see any AT-only connections so I doubt that's your problem.

Hocrest
10-04-2008, 11:34 AM
Never mind, I'm an idiot...

I took the car to AZ this morning to check the codes. One for signal from the TCU (1722), I was expecting this one. I also got a code for the MAF. As the clerk was trying to sell me a can of MAF cleaner, I had a vision in my head of the MAF wire dangling next to the valve cover. :roll:

Went out, drove around the side of the building and popped the hood to confirm. Yep, I never plugged it in (doh). The slight stuttering and richness seems to be gone. :grin:

I think I found the pin (#81) I need to ground to let the ECU know that I have a MT, I'll post to confirm when I try it out.

Huffer
10-04-2008, 05:38 PM
Wow, nice job on the swap... it's amazing how something as simple as an unplugged sensor slips by when you've done something as cool as a tranny swap. :)

filter27e
10-05-2008, 09:50 PM
I've been wanting to do this every since I bought my car. I had convinced myself that I would need an automatic with a child on the way. Yeah, I didn't need one that bad after all :-(

Hocrest
10-05-2008, 10:09 PM
I spent some more time going through the FSM's over the weekend. I think the easy fix for the ABS is to grab a MT ABS computer.
I grounded pin 81 of the ECU, the CEL did go out. But it's back again, I'll get the codes tomorrow to see what's going on...

AussieDan
10-06-2008, 06:36 AM
Damn, guess I missed the (MT) notation on pin 81, interesting.

Does your car have a separate ABS controller at the base of the passenger a-pillar (next to the blower motor) or the later integrated unit (with everything built into the actuator in the engine bay)?

Hocrest
10-06-2008, 07:49 AM
Damn, guess I missed the (MT) notation on pin 81, interesting.

Does your car have a separate ABS controller at the base of the passenger a-pillar (next to the blower motor) or the later integrated unit (with everything built into the actuator in the engine bay)?

I didn't find pin 81 in the schematics. It wasn't until I started going through the pages of ECU diagnostics that I found it.

For the ABS?? I don't know, I'll have to take a look.

subba
10-06-2008, 10:18 AM
did you reset the ECU?

Hocrest
10-07-2008, 04:26 PM
I reset the ECU this morning, and after driving around for a bit to run some errands, it hasn't returned yet.

I got a PM asking about the ECU wire I grounded. It was pin 81. There was no wire in that spot, so I had to improvise. To help ID the correct space 79-L, and 82-LR.

I also got the cruise control working again today, It was easier than I thought. On the plug on the CC unit I removed the pins 3-GY and 4-LR (LgB in Canada). That is all you need to do to get the cruise working. But, unless you wire in the front/blue switch on the clutch pedal, the engine will rev high if you have the cruise set and go on the clutch. To take care of that, splice the clutch switch into series with the 1-YW wire on the brake switch.

I was going to wire in the back clutch switch, so that the clutch has to be engaged to start the car, but I decided to leave it as is.

As long as the CEL stays out, I'm pretty much done with the swap. Like I mentioned, I'll grab a MT ABS unit, next time I'm at the yard.

Hocrest
12-26-2008, 06:08 PM
Just thought I'd update this thread. I continued to have an issue with the CEL returning after about 90 minutes of driving.

I finally got an ECU out of a 97 MT, swapped that in and no no more CEL. So if anyone else is going to do this swap and wants to avoid the CEL, get the ECU as well.

T_F_E
12-26-2008, 08:15 PM
So how much in total did this swap cost? I really really want to do this

Hocrest
12-27-2008, 10:36 PM
So how much in total did this swap cost? I really really want to do this

That's gonna depend on where you get your donor trans. All together I'm under $300.

$100 --Trans, Starter, Linkage, pedal box, flywheel (From a U-Pull yard)
$40 --Flywheel cutting
$120 --Ebay clutch
$20 --Gear Oil

T_F_E
12-27-2008, 10:39 PM
wow... how long did it take you?

Hocrest
12-27-2008, 11:51 PM
wow... how long did it take you?
I did the swap itself in a day. But I've done my share of swap's with other Subaru tranny's. And then a few hours on a few other days to sort out the little wiring differences.

If you know what your doing, this could easily be done in a weekend.

subba
01-06-2009, 01:21 PM
dont forget the M/T driveshaft.

Thanks for giving us a update BTW, i like when members not leave us hanging lol :smt023

Hocrest
01-07-2009, 09:03 AM
dont forget the M/T driveshaft.
Yeah, forgot to list that...

You can get just the front half of the driveshaft though. Which is helpful since Harry's started charging for two driveshafts when you get a Soob driveshaft :smt012

Blackheat68
06-14-2009, 07:58 PM
what kind of "little wiring differences" did you face?


how hard were they to overcome?

Benfolio
06-17-2009, 01:03 PM
Huh. Never saw this thread before. Good to know about the cruise fix. I can deal with no ABS, but cruise? Nah.

i STILL haven't wired mine correctly. I have all the harnesses and modules out of the '97, but have been too lazy to splice, or swap, them into the '98 to take care of the NSS, the CEL (due to the NSS being in neutal all the time), the ABS, and the cruise.

Hocrest
12-12-2009, 08:40 PM
what kind of "little wiring differences" did you face?


how hard were they to overcome?

Sorry, just saw this post...

Other than the ones mentioned earlier in this post, the only one I can think of is wiring the reverse switch into the harness that went to the indicator on the AT.

-There are two switches on the MT trans, use a meter to check for continuity. One will be closed when in "R", the other will be closed anytime you're in a gear. Use the one that's closed when you're in "R"

-From the AT to the chassis there are 2 large connectors, the smaller of the 2 went to the indicator on the side of the trans. Determine which connectors sense "R" and wire the 2 wires from the "R" switch on the MT into those. It's continuity so polarity doesn't matter.

daleyswanson
12-21-2009, 09:46 PM
i wanted to do this but i figure i will do it when i swap in another engine, and just do engine, tranny and ECU to match it all. thats awesome you did it for 300 though. that part caught me off guard