Splice or Swap EJ22t harness

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Should I splice or swap?

Splice
6
86%
Swap
1
14%
 
Total votes: 7

mTk
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Splice or Swap EJ22t harness

Post by mTk »

Should i swap the ej22t wire harness into my legacy, or add/splice in the new 22t specific sensor wires that i need. For those of you that have swapped in a 22t, what did you do?

I am getting the entire car harness. Can i seperate out just the engine specific parts?

Thanks in advance for your ideas and advice,

MK
1992 BC672 AWD 5MT
ciper
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Post by ciper »

Neither?

Are the few additional leads missing? I though the wires existed but weren't connected to anything. Even if they dont exist why not just wire the 3-4 extra wires yourself outside the harness?
mTk
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Post by mTk »

That's what i meant by splice, run new wires from the additional sensors to the ecu. Additionally, from looking at the pinouts some of the sensor +/- are switched on the turbo ecu.

MK
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Post by vrg3 »

Don't run a new harness.

Look at these pinouts:
http://www.graphics.cornell.edu/~v/ecupins/

All you have to do is run 5 new wires: the pressure sensor's power, signal, and ground wires; the pressure exchange solenoid wire, and the boost control solenoid wire.

You would of course also have to supply the two solenoids with +12v on the other side. Potential sources would be the +12v supply to the idle air control valve or to the canister purge control solenoid. The only reason those would be a problem would be if the wire is too light a gauge to handle the extra current (I don't remember off the top of my head; it shouldn't be a big deal though).

You could get away with leaving out the pressure sensor's power and ground if you just tap the TPS power underhood and use any convenient ground. A ground from another sensor would be better than the chassis, though, since it would go back to the ECU directly.

Then you'd just have to switch the cam and crank angle sensor signals. Each has three lines (+, -, and shield). But, you could probably get away with just swapping the + lines. Check your particular ECU, but the several BC/BF ECUs that I've examined internally connect both shields and both - lines to ground anyway, so it would make no difference. I haven't looked closely at the connectors underhood, but it also may be possible to just switch the connectors there at the back of the engine block.

It's easy to add and remove wires from the ECU's harness connectors. If you look at the yellow connectors you can see that you first have to undo the locking plate with two flathead screwdrivers (each row of pins has one and they are held in by tabs at either end). Then, you can use a large needle to reach in through the front and push the plastic locking tab off the contact and pull the wire with contact out. Adding a wire is much easier, since you start with a wire with the crimp-on contact already attached, and you just push it in until it clicks.

It sounds like you already have the EJ22T harness so you could take the wires you need off of it, and the connectors for the parts underhood from it too.

Adding in the 4 new contacts (boost control solenoid, pressure exchange solenoid, pressure sensor signal), running those 4 wires through the firewall, tapping the three engine-bay lines (IAC valve power supply, TPS power supply, MAF sensor ground), splicing the three connectors on underhood, and swapping the cam and crank "+" pins should actually be pretty easy. I could probably do it in easily less than an hour. If you're not as familiar with the systems it still shouldn't take too long.
"Just reading vrg3's convoluted, information-packed posts made me feel better all over again." -- subyluvr2212
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Post by mTk »

I have a printout of the ecu pinout from previously, it is EXTREMELY helpful and easy to read, thanks!

It really sounds like splicing is the way to go, hell, i probably won't have to actually 'splice' (ie solder) anything together. I don't have the harness yet (2 more days) but i'll prolly remove the wires from it for the sensors that are turbo specific.

MK
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Post by vrg3 »

mk750 wrote:I have a printout of the ecu pinout from previously, it is EXTREMELY helpful and easy to read, thanks!
You're welcome.
It really sounds like splicing is the way to go, hell, i probably won't have to actually 'splice' (ie solder) anything together. I don't have the harness yet (2 more days) but i'll prolly remove the wires from it for the sensors that are turbo specific.
Well, you'll probably have to crimp/solder at least when you tap the +12v for the solenoids and when you attach the connectors for the new parts.
"Just reading vrg3's convoluted, information-packed posts made me feel better all over again." -- subyluvr2212
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Post by mTk »

Will the turbo ECU run the n/a engine, even if just in limp mode? I may do all the wiring and all the prep work for the install, then drive the car to a friend's for the remainder.

MK
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Post by vrg3 »

It should, yes, but your air/fuel ratios and ignition timing will be a little off. If you drive very gingerly you may be okay.

If you don't install the pressure sensor, pressure exchange solenoid, and boost control solenoid, you'll get check engine lights for all three and a fuel cut above about 40% throttle.

That fuel cut may actually be desirable as it can help keep you from driving the car harder than is safe with the wrong ECU.

Keep in mind that you can do all the prep work except for swapping the "Cam Angle Sensor (+)" and "Crank Angle Sensor (+)" wires while still using your NA ECU. The wires for the solenoids and sensor just don't go anywhere in the NA ECU. Then when you're ready, swapping those wires is really only a five minute job.

Oh, and I checked in the service manual -- the cam/crank sensor negative wires and shields are indeed all internally grounded in the ECU, so you do only need to swap the + lines of the sensors.
"Just reading vrg3's convoluted, information-packed posts made me feel better all over again." -- subyluvr2212
mTk
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Post by mTk »

Sweet, thanks for checking that out. The install should go pretty smoothly.

MK
1992 BC672 AWD 5MT
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