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Old 11-03-2010, 05:00 AM   #1
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Member#: 180769
Join Date: May 2008
Chapter/Region: NESIC
lots of junkers

Default "Power Mode" for 95-98 legacy 4EAT's

As you may or may not be aware, early 90's SVX's came with a power mode button in Japan. US models didn't get it, probably for EPA fuel milage reasons. But the pin on the Transmission Control Unit was still there and the programming code still existed in the US TCU's. So it's popular in the 91-94 legacys to move the female pin on the 20 pin connector from postion 6 to position 4. This then makes the "manual" button on the shifter turn on the "power mode".

Power mode is the equivalent of a sport shift button on a newer car. The TCU uses a different shift map so that it holds gears longer, downshifts sooner, and won't lock the torque converter clutch. It makes the transmission much more responsive and fun to drive. There is a small gas milage penalty, around town it's only a MPG or 2, but on the highway it is more because of the torque converter not locking up.

So in 95 subaru switched to OBD-II. This required a complete redesign of the ECU (engine control unit), wiring harness, and TCU. All the pins on the TCU that used to control the "power" and "manual" lights on the dash and the input for the manual mode button have been redesignated as communications lines for the OBDII systems. The TCU case and board have also been redesigned with the plugs on the side instead of the bottom. But through this all, pin 4 on the 20 pin connector was still left unused.

I pulled a pin and pigtail of wire from a 20 pin TCU connector on a spare harness and put it in postion 4, which is the only unpopulated pin on the latching tab side of the 20 pin connector, which is the higest connector up on the TCU. The TCU is to the left of the brake pedal above the drivers feet by the way, big gold box with 3 connectors. You have to release the locking bar on the back of the connector, push the pin in until it clicks, fold the locking bar back into postion and plug the connector back in.

Power mode is activated by grounding pin 4 on the early TCU's. I grounded pin 4 on the 97 OBDII TCU and while it can no longer light up an indicator of power mode being activated you can tell by driving. At part throttle at 45mph it was holding 3rd gear with the engine up around 3k rpms. Unground pin 4, it would shift to 4th and lock the TC dropping the RPMS down in the same driving conditions. It downshifts as soon as you roll into the throttle, rather than having to stab the throttle to WOT to getting it to downshift like you normally do. Much more responsive and fun to drive.

All you need for the mod is a small switch, some wire, and a TCU pin and pigtail. Set up the switch to ground pin 4 of the 20pin TCU connector to a chassis ground and you will have sport mode on command. This should work for a 95-98 TCU, outback or legacy. I'm not sure about the 99's as they changed some things with the bellhousing pattern and ABS sensors among other things and I don't have a 99 handy to test with. I'll try out a 98 outback tomorrow.

Here's a picture borrowed from "Nomake Wan" on subaru-svx.net

Depending on if newer Subaru's kept the separate TCU and the same plug arrangement this could be tested on MY 2000+ ones too.

Here's a great site for further reading on the subject: http://www.alcyone.org.uk/ssm/index.html
Reprogramming earlier TCU's and ECU's is discussed.
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Last edited by WoodsWagon; 11-03-2010 at 05:25 AM.
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Old 11-04-2010, 09:44 PM   #2
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Member#: 74907
Join Date: Nov 2004
Chapter/Region: NWIC
Location: salem, OR
98 cam'd EJ251
Wrx Tranny,slowr than ish


If only I learned this trick before I swapped in a wrx tranny.....

Good info, should definitely help some people hold on to their auto's for a while before caving like I did. Must be nice to step on the gas and have the car downshift, instead of having the stab the hell out of the gas peddle to get the tranny to do something.

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Old 10-31-2012, 09:30 PM   #3
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Join Date: Oct 2012

this sounds really cool. I've driven a 95 legacy (just bought a second one) for about 5 years now and i've always wished it would be more responsive shifting. I had sort of learned how to ride the gas to do what I want but this sounds great. I would need some help wiring the switch and I have to fix some issues with the car first, but thanks for the tip!
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Old 11-01-2012, 01:12 PM   #4
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Join Date: Apr 2002
Chapter/Region: Tri-State
Location: NJ
'06 WX8


WoodsWagon: that's a nice piece of knowledge, thanks for finding out. I have to this on the (now handed down) '95 Impreza. It even has some spare slots for switches in the cluster bezel. My previous "mod" was swapping a '93 "PRND21" indicator into the cluster.
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Old 11-01-2012, 07:06 PM   #5
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Join Date: Nov 2010
Chapter/Region: Tri-State
Location: Jersey Shore, Pa
2002 wrx


i did this mod a while back and it's well worth it. not hard to do.
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Old 06-26-2014, 10:59 AM   #6
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Member#: 394480
Join Date: Jun 2014
Location: New Hampshire
1998 Legacy Brighton


I HAVE to do this to my doggy 2.2 wagon, cant even get it to shift when touching the bumper with my foot driving up mt ascutney in Vermont. pretty sad. definitely not an electrician though so if someone who has done this could possible post a picture of what pin is moved where or something close, ill update you guys with how it turns out.
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Old 08-27-2014, 05:05 PM   #7
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Anyone do this ? Just got a 98 Legacy GT and the shift times are sooooo slow. Pictures would be great
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Old 12-01-2014, 02:37 PM   #8
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Join Date: Aug 2014
2003 Legacy


Anyone know if this works for newer transmissions/TCUs, i.e. TZ1A4 and the AG33A TCU?
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Old 01-26-2015, 08:29 PM   #9
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Join Date: Apr 2004
Location: N. Idaho
2002 WRX GG>>
2016 Focus RS


^ I'm working on this for my '02 WRX...I grounded the Power* mode pin (connector B55/23), and it did nothing..... maybe the TCU is just not programmed for this.

I have read this will work on the '99+ USDM NA cars. It would be the White B54 / 20 pin (there shouldn't be anything plugged in) - it's based on looking @ the connector from the side the wires enter w/the latch on top.

* Referring to an EDM TCU IO pinout from the FSM. The JDM/EDM/ADM got the Power and Hold (winter) option (rocker button next to shifter- NOT the same as the early '90s Subaru's w/the 'MANUAL' button) AND/OR the Sport Shift on certain '99+ models. I'm sure the Sport Shift is a different transmission, but 'hoping' the Power mode is just grounding a pin on the TCU / TCM.

If I can't find the pin to ground, I'll be looking for a TCU from an overseas model....but it'll have to be one w/OUT the sport shift and VDC control otherwise I'll probably get an AT CEL since I won't have those hooked up to anything.

Do a SEARCH for "power mode subaru" on Google and you'll find LOTS of info, too.

For the older models - '92-'98 - here's the idea:

Last edited by wtdash; 06-19-2015 at 04:33 PM.
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