Eg33 swap......obd1 ECU with obd2 TCU

[EastCoastEJ22T]

I have a 1995 legacy running an OBD1 Eg33 from a svx. I am using the obd2 legacy transmission and TCU.

 

Basically..... I replicated the TCU to ECU interface from the 1995 legacy by splicing into the signals from the OBD1 svx ecu.

 

In total there are 7 wires that go from the leg TCU to the leg ECU on my 1995. I have 5 of them figured out and spliced, but don't know what to do with the last 2 wires.

 

 

--- LEG TCU ----- SVX ECU

#1. B56-19 ----- B60-3 ======TPS power

#2. B54-8 ------ B60-2 ====== TPS signal

#3. B54-9 ------ B60-5 ======MAF signal

#4. B54-5 ------ B61-16 ======Engine Speed Output

#5. B55-16 ----- B59-20 ======Torque control signal

#6. B56-16 ----- ??? =======Torque Control Cut Signal (no pin on ecu)

#7. B55-11 ----- ??? =======AT diagnostics signal (no pin on ecu)

 

The good:

-The car shifts fine through all four gears. It pulls hard and acts normal, although maybe a little to aggressive on the up-shifts due to the lack of a Torque Control Cut Signal.

 

The Bad:

-The torque converter will not lock-up at highway speeds.

-Flashing ATF light on start up, goes away after a few seconds and does not return.

 

Any input or advice is greatly appreciated.

 

Cheers,

Ian

[idosubaru]

Have you compared schematics for them? Wonder what the difference is?

 

Would an OBDI or SVX TCU offer any advantages? a TCU that matches the ECU would seem to have some advantages and TCU's are a dime a dozen. I have one that's not worth much to me.

[EastCoastEJ22T]

Have you compared schematics for them? Wonder what the difference is?

 

Would an OBDI or SVX TCU offer any advantages? a TCU that matches the ECU would seem to have some advantages and TCU's are a dime a dozen. I have one that's not worth much to me.

 

I have both an obd1 scx tcu and obd1 legacy tcu already on hand.

 

The wiring and pinots are not even remotely similar. You would have to rewire the complete sytem, and switch all the trans sensors over to the OBD1 versions.

 

I am mainly looking for a method to replicate those two TCU pin requirements. Either by tapping into the SVX ecu or somewhere else in the body harness.

 

I am not even sure what the AT diagnostics signal is for?

[ausubaru92]

The 4EAT of the OBD1 style is a different control system to the later 'Series 2 4EAT'.

 

If you are using a series 2 box, you will need the series 2 TCU

 

Torque control just sent a signal from the TCU to the ECU to reduce timing momentarily while the transmission changes gear. Will work fine without it.

 

The AT diagnostics signal is part of the OBD2 communication system, not required for normal operation.

 

As for not locking up, the TPS on some early models was reversed to later models, maybe you will need to invert the signal from the TPS to the TCM

[EastCoastEJ22T]

I tried switching the TPS wiring and still no torque converter lock up. It was worth a try.

[WRX2FFU]

I am not sure but torque convertor lockup may be able to be done with a switch.

 

I am not sure if the subie TC lockup solenoid needs voltage or ground?

 

I know on chevy 200r4/700r4 you can wire a switch in for TC lockup for highway use. Lots do it for trans swaps.

[EastCoastEJ22T]

I don't see a specific pin on the TCU pinout that triggers the Torque converter lock-up.

 

Does anyone know if the tourque converter is mechanically actuated or electrical?