Howto: 89+ ECU HAC mod

[GrimJack]

First off, I don't suggest trying to do this unless you are very handy with a soldering iron, and perhaps not even then. If you wreck your ECU trying to duplicate this, it's only your own fault. The only guarantee I provide is that this will be a pain in the ass.

That said, here's the deal. You need to do this if you plan to install a MAFT or MAFT Pro and will be travelling between different altitudes. You'll need to solder on two wires (well, you only need one, unless you decide to go back to stock, so you might as well do them both) and cut a trace on the board. I have some high res pics of both of these, I highly suggest that 56k customers go get high speed internet before attempting to look at these.

Feel free to post questions, I'll do what I can to answer.

 

[dbsupra90]

thanks for the pics.

my only suggestion would be to rtv the wires to the board near the solder joint and maybe once again 1/2 way down the wire. w/ the wire ends bent 90* like that vibration could break it loose over time.

 

[boltz]

Good pics Grim. Is this your own handy work? how did you get the info on what to do? Did you copy a modded ECU?

 

[TurboStreetCar]

just curious, what do u do with those 2 wires? do they wire into the maft pro? or do they go to a sensor that you have to buy? i have the GEN 2 but i pretty much stay in my town so im not worried about doing it, just curious about what its all about.

 

[boltz]

1 of the relocated HAC wires hook up to the pro, the other is left disconnected from what i understand. No extra parts needed.


Edit:

Grim, so based on your pictures, the MaftPro wire hooks up to the yellow wire you have in that location?

 

[GrimJack]

If you want to use the internal HAC, you just connect the two wires.

If you want to hook up a MAFT / MAFT pro, you connect the output wire from the MAFT to the yellow wire.

These pics are of my personal ECU, and yes, those crappy solders are my work. I've been in contact with one of the original guys from SoCal that figured out how to do this mod, he sent me some hints and advice.

PS: The D IS121 5J19 module is the internal HAC sensor.

 

[tekdeus]

I'd like to learn more about why this is required, to what altitude extremes, and also if this pertains to pre 89 ecu's.

 

[Jeff Lange]

Pre-89 ECU's have an external HAC sensor, hence there is no ECU modding required.

 

[chriso]

Great info for the long hidden secret of HAC Modding !!! +1 to you sir :boink: I think I would send mine out to the MAFT Pro people for them to do it though.

EDIT: Tried to rep you but realized you are a moderator and can't be repped...oh, well good info, nonetheless !

 

[boltz]

it is fairly easy from what i can see... about the hardest part is cutting that trace, but nothing a modeling xacto cant handle.

 

[drjonez]

HAC mod connections:

http://www.4cefed.com/maftpro/'89+%20HAC.pdf

 

[hottscennessey]

*cough* (pre-89 FTW) *cough*

Great writeup!

 

[boltz]

I am guessing since Dr.J hasn't responded in my PM on (SF) saying anything wrong with Grims pics then i have to assume they are correct.


So Grim, I guess you have this hooked up and running your car?

 

[drjonez]

I am guessing since Dr.J hasn't responded in my PM on (SF) saying anything wrong with Grims pics then i have to assume they are correct.

sorry, quite busy.

 

[GrimJack]

Nope... still a foot of snow on top of my Supra, and the doors are frozen shut. I'll post up as soon as I have it running, believe me.

 

[Daves2JZGTE]

Wow this all sounds familiar to me. LOL

Not that I know anything...........

This was a well-kept secret for many years. Now the info is out.

As for hints id say i gave you a map. LOL


Dave

 

[drjonez]

ok?

 

[Y.O. supra89T]

this should be a sticky or at least in faq
very helpful!!!
great info
keep it coming guys

 

[boltz]

I moded my ECu but have not tested yet. Nor is there confirmation from anyone. It is great info.

The secret shouldnt have been kept because it is not a money maker especially when they mod your ECU free minus shipping costs and down time which is the real pain for me. Especially when i am fully capable of soldering.

 

[Daves2JZGTE]

I told them they could share the info with anyone they wonted they just couldn’t make money from it. I did ask for the credit though. Glad to hear they modded them for free. Grim was only the second person to ever ask me how to do it.

Dave