BAC/ECU Fix
05-14-02, 02:36 PM
#1
Nothing to see here.
Thread Starter
BAC/ECU Fix
If after performing all of your tests, you find that the BAC is not receiving it's signal from the ECU you may want to try this fix (As far as I know, this is for the Series 4 NAs). You will need to have a good small-point soldering gun, desoldering tape and TIP120 Darlington transistor (Radio Shack # 276-2068.)
1. Remove ECU from passenger footwell
2. Remove both covers from the ECU (lots of screws)
3. Carefully fold the top board out of the case
4. With the plugs facing you, (see attached image) you should see 2 rows of transistors—they are on the left side. The transistor you are going to be replacing is labeled on the circuit board as "T801"
5. Carefully flip the ECU over and find the three points that the transistor posts come through the board—desolder these three points using desoldering tape available at Radio Shack.
6. You will now need to bend the posts of the new transistor to fit in the now vacant holes on the board and solder the new transistor in.
7. You're done with ECU. Put it back together.
NOW BEFORE YOU RECONNECT CHECK THE CONNECTORS AT THE BAC!!!! If they are touching or are capable of touching you will need to make a new connector that will not short out. When those two wires touch it blows the transistor! I replaced my connectors with shielded Radio Shack brand spades. The OEM connector just plain sux. The plastic was brittle and the connectors slipped out and shorted. Good luck!
B
1. Remove ECU from passenger footwell
2. Remove both covers from the ECU (lots of screws)
3. Carefully fold the top board out of the case
4. With the plugs facing you, (see attached image) you should see 2 rows of transistors—they are on the left side. The transistor you are going to be replacing is labeled on the circuit board as "T801"
5. Carefully flip the ECU over and find the three points that the transistor posts come through the board—desolder these three points using desoldering tape available at Radio Shack.
6. You will now need to bend the posts of the new transistor to fit in the now vacant holes on the board and solder the new transistor in.
7. You're done with ECU. Put it back together.
NOW BEFORE YOU RECONNECT CHECK THE CONNECTORS AT THE BAC!!!! If they are touching or are capable of touching you will need to make a new connector that will not short out. When those two wires touch it blows the transistor! I replaced my connectors with shielded Radio Shack brand spades. The OEM connector just plain sux. The plastic was brittle and the connectors slipped out and shorted. Good luck!
B
05-15-02, 07:47 AM
#4
Nothing to see here.
Thread Starter
I'm surprised that this thread didn't get more views!
The total time to do this is about an hour, including pulling the ECU from the car. Is it that people are fearful of touching their ECUs? I wouldn't even call that thing a computer—my electric toothbrush is more sophisticated!
I guess I should have stated that this fixes the problem with the engine idle when accessories (AC, PS) are turned on. So, if your car stalls when you turn the AC on or your idle drops when turning the wheel this may fix it.
I should also note that I gleaned this fix from several posts that seem to have gotten lost last year when the server went down.
B
The total time to do this is about an hour, including pulling the ECU from the car. Is it that people are fearful of touching their ECUs? I wouldn't even call that thing a computer—my electric toothbrush is more sophisticated!
I guess I should have stated that this fixes the problem with the engine idle when accessories (AC, PS) are turned on. So, if your car stalls when you turn the AC on or your idle drops when turning the wheel this may fix it.
I should also note that I gleaned this fix from several posts that seem to have gotten lost last year when the server went down.
B
05-15-02, 11:02 AM
#6
Junior Member
Join Date: Apr 2002
Location: virgina
Posts: 11
Likes: 0
Received 0 Likes
on
0 Posts
Yo thanx man i just asked this same question like two days ago but got nothing that was even revelent i have a 87 turbo 2 and the test for checking the ecu is using a 1/4 wat 10 ohm resistorand sticking it in the bac valves plug and meshure the ac voltage between between the resistor if it coes up between 6 and 7 volts you are in the green but any thing below 5 and your probley got a shot transistor and need to do this mod do you. the only thing is i dont know how to fox the 87 turbo 2 bord i know how to sodier but i dont know what transistor it is and ime no genioous with wiring charts so if you can help me that would be great
Trending Topics
07-01-02, 02:27 PM
#8
Persona non grata
Crap ... finally got around to yanking the ECU in my '90 Vert to do this. Then I realized this writeup was for the 86-88's. Does anybody know which transisitor is responsible for the BAC on the 89-91 ECU's?
07-01-02, 03:25 PM
#9
HAILERS
Join Date: May 2001
Location: FORT WORTH, TEXAS,USA
Posts: 20,563
Likes: 0
Received 22 Likes
on
20 Posts
http://www.teamfc3s.org/info/articles/idle.html
https://www.rx7club.com/forum/showth...threadid=90036
https://www.rx7club.com/forum/showth...threadid=90036
Last edited by HAILERS; 07-01-02 at 03:27 PM.
08-17-02, 12:36 AM
#10
Round&Round not Up&Down
Join Date: Aug 2001
Location: West Bloomfield, MI
Posts: 2,805
Likes: 0
Received 0 Likes
on
0 Posts
I've gone through the tests and came to the conclusion that I had a bad T801 transistor. I've got the replacement transistor from RS and I removed the ECU hoping to find this transistor. I see the T801 written on the board, but the transistor looks fine. Should it be burned in some way, or is all of the damage internal and will not show any signs of being bad?
08-19-02, 10:28 AM
#11
Round&Round not Up&Down
Join Date: Aug 2001
Location: West Bloomfield, MI
Posts: 2,805
Likes: 0
Received 0 Likes
on
0 Posts
I soldered the new transistor in, but I'm not getting the correct reading at the green wire on the BAC at idle. Is there a right way and a wrong way to solder the transistor in? I didn't see any polarity marks on the board or the piece itself........
03-06-03, 09:44 AM
#15
Persona non grata
Reviving an old thread. Does anybody have a pic of the transistor that needs to be replaceon a '89 - '91 ECU? That pic is for a '86 - '88, and it's completely different.
03-06-03, 05:39 PM
#18
Nothing to see here.
Thread Starter
I'm downloading the FSM now to take a look. Just have to get my son to stop bugging me to "change maps!" on Unreal Tournament...he's 5.
03-06-03, 06:47 PM
#20
Senior Member
Join Date: Sep 2002
Location: Louisiana
Posts: 613
Likes: 0
Received 0 Likes
on
0 Posts
While we are on the ECU--here's a question....I have an 86 NA, and I am now working on the "no starting" problem(gonna do the ATF trick tomorrow), but when it was running, I had the usual lag between 3700 and 4000. I have seen all the posts about how this is when the 5 and 6 ports open, and I have no desire to wire them shut. I heard someone once tell me that there was something you could do to the ECU to fix this....anyone know what it is??
03-06-03, 08:20 PM
#22
Nothing to see here.
Thread Starter
Originally posted by skydivr73
While we are on the ECU--here's a question....I have an 86 NA, and I am now working on the "no starting" problem(gonna do the ATF trick tomorrow), but when it was running, I had the usual lag between 3700 and 4000. I have seen all the posts about how this is when the 5 and 6 ports open, and I have no desire to wire them shut. I heard someone once tell me that there was something you could do to the ECU to fix this....anyone know what it is??
While we are on the ECU--here's a question....I have an 86 NA, and I am now working on the "no starting" problem(gonna do the ATF trick tomorrow), but when it was running, I had the usual lag between 3700 and 4000. I have seen all the posts about how this is when the 5 and 6 ports open, and I have no desire to wire them shut. I heard someone once tell me that there was something you could do to the ECU to fix this....anyone know what it is??
Amur-- LOL! Since I got the 91 TII I've really not had any problems so I haven't been contributing as much and picking HAILERS' brain. Where is he and that damned scanner!?! I love when he puts car parts on the scanner!!!
Brian
I hope it's not his! 
03-06-03, 10:54 PM
#24
HAILERS
Join Date: May 2001
Location: FORT WORTH, TEXAS,USA
Posts: 20,563
Likes: 0
Received 22 Likes
on
20 Posts
Here, I finally found it: http://home.earthlink.net/~burntoast/3700.html