Emission Computer testing? (1 Viewer)

gregnash

Anal Retentive Analyst
SILVER Star
Joined
Nov 4, 2011
Messages
11,840
Location
Carson City, NV
 
So I confirmed last night that my ECM is dead (did short jumper wires and reconnected the ICS like normal). I had grounded the ICS to the carb body (Green Wire mod) and the truck runs fine but after doing some further reading from JimC it appears while this is a fix, it really is not one but more of a bypass.

From the reading I have done, while grounding the ICS allows it to function it does not FULLY function like it should. My understanding is that the ICS performs multiple duties between the ECM and Vac that it sees during normal operation. It basically becomes a meter of the amount of fuel that is let into the carb based on reading from the computer and vacuum from the fuel cut switch.

From what Jim has said in other posts basically once you do the Green Wire mod and ground the ICS to the carb body it keeps it in basically an open state anytime it is energized. This is not necessarily great for the engine because it causes excess fuel usage and thus that fuel has to go somewhere (like the cylinders, out the exhaust, in the cat and out the tailpipe, destroying everything slowly as it does).

So with that said, before I drop $50 on a used and supposedly good ECM for BeBe, is there a way to test mine to see that it is truly the culprit and I do not have a break in the grounding wire somewhere. I am not an electrical person so this will have to be dumbed down for me.

I will pull FSMs when I get home but at work I cannot pull up dropbox or any other such site (web security).
 
Joined
Mar 31, 2014
Messages
4,468
Location
Gone
The test to check if the emissions computer is working (for what you're interested in) is easy and detailed in the emissions FSM. See Deceleration Fuel Cut (Attached).

If all the test procedures work according to the FSM, the computer works for dec fuel cut.

If the vacuum switch and fuel cut solenoid work but deceleration fuel cut test fails, the computer is toast.
 

Attachments

Spike Strip

Midnight Rider
SILVER Star
Joined
Nov 22, 2005
Messages
14,796
Location
Lexington
 
 
ECM works by controlling the ground circuit. Common for these to fail, and it's usually the points where the connector is soldered to the board. If you're handy with a soldering iron, you can try re-flowing those connections. If not, and the ECM is bad, try and find an old-skool audio repair person around you. It's nothing for a tech to test and repair a CB like this as it's very simple, and I'd rather have one repaired/tested than spend money on one that has the same issues.

I don't know of any specific test, other than what OS posted as an indirect test, or testing the board with a multimeter.

FWIW, I had one that was driving me crazy as the failure was intermittent, so sometimes truck would idle, other times die. Finally swapped out the ECM for a NOS one and all has been good since. Fingers crossed. Knock on wood.
 

gregnash

Anal Retentive Analyst
SILVER Star
Joined
Nov 4, 2011
Messages
11,840
Location
Carson City, NV
 
ECM works by controlling the ground circuit. Common for these to fail, and it's usually the points where the connector is soldered to the board. If you're handy with a soldering iron, you can try re-flowing those connections. If not, and the ECM is bad, try and find an old-skool audio repair person around you. It's nothing for a tech to test and repair a CB like this as it's very simple, and I'd rather have one repaired/tested than spend money on one that has the same issues.

I don't know of any specific test, other than what OS posted as an indirect test, or testing the board with a multimeter.

FWIW, I had one that was driving me crazy as the failure was intermittent, so sometimes truck would idle, other times die. Finally swapped out the ECM for a NOS one and all has been good since. Fingers crossed. Knock on wood.
Thanks @Output Shaft but system wont let me download here at work. I am pretty sure that I have that manual in my dropbox and can access at home. Thanks for pointing out which section to look in.

And @Spike Strip I may give this a try. For the full delete of this, you basically need to have keyed power to the HOT side of the ICS correct? So basically I could temporarily put something inline to power the ICS while I look at the computer and possibly try to repair.
 

Spike Strip

Midnight Rider
SILVER Star
Joined
Nov 22, 2005
Messages
14,796
Location
Lexington
 
 
Got the ECM many years ago when they were still available from Toyota. Paid whatever Mr. T was asking, then. FAIK, they are still available from Japan, but something a little South of $500!

There is constant 12v to ICS when the key is on/run. You don't need to do anything to it, other than ground it if you want it always 'on' .

Again, you *should* be able to get these repaired for a 100 bux or so if you can find a Vintage Hi-Fi repair shop that is willing to look at it. I gave up in Los Angeles because I don't speak the language of the current crop of repair people... :p

When I was a younger pain-in-the-arse, there used to be a ton of old Lockheed Skunk Works guys around who repaired this kind of stuff on the side (and loved doing it), but they're all gone, now.... :( Used to take all my Vintage Marantz and Mcintosh Hi-Fi stuff to them. But this was before the telegraph was invented, mind you. :rofl:
 

rusty_tlc

Dain Bramaged Member
Joined
Jun 23, 2005
Messages
13,926
Location
Reno, NV
 
 
 
Are you calling me old? :flipoff2:

If it is something I can spot visually like a solder fracture on the PCB I might be able to fix it.

I am going to try to get to the meeting tomorrow think you can bring it?

(If I can't make the meeting I live nearby and you could drop it by my house.)
 

gregnash

Anal Retentive Analyst
SILVER Star
Joined
Nov 4, 2011
Messages
11,840
Location
Carson City, NV
 
Possibility that I may be there... however it is still attached to the truck and needed for it to run (at least that is what I am reading at the moment) as I have not don't a switched hot connection for it.

And I would never call you OLD Dan.... at least not to your face!
 
Joined
May 5, 2016
Messages
54
Location
HI
Definitely going to follow this thread @gregnash as Im having the same issue and want keep my ICS working like it should, yet as with many, I've got it grounded to carb. I have a solder gun, so tomorrow after work, I'm gonna open up the ECM and give it a good visual to look for any solder cracks. if thats the case I think i still have the skills to do it, past that, its all magic in there!

I should add that my ICS works and fails randomly when hooked up to the ECM. That tells me its a connection problem that relates to the solder cracking problem.
 
Last edited:

rusty_tlc

Dain Bramaged Member
Joined
Jun 23, 2005
Messages
13,926
Location
Reno, NV
 
 
 
The test to check if the emissions computer is working (for what you're interested in) is easy and detailed in the emissions FSM. See Deceleration Fuel Cut (Attached).

If all the test procedures work according to the FSM, the computer works for dec fuel cut.

If the vacuum switch and fuel cut solenoid work but deceleration fuel cut test fails, the computer is toast.
I just looked at the PDF, Toyota had a habit of calling any collection of logic chips a computer. The good news is the "computer" is probably a few comparators and some logic gates. The bad news is they are probably TTL logic which hasn't been made in low these many years. If anybody has a spare I'd love to reverse engineer it.
 
Joined
Mar 31, 2014
Messages
4,468
Location
Gone
Computer looks to have only four inputs:

1. Coil
2. Vacuum Switch
3. Cat Temp Sensor
4. Speed Sensor (don't know how it gets that info)

The deceleration fuel cut system is only using RPM (coil) & vacuum switch input (on/off). Super simple.


image.jpeg
image.jpeg
 

NeverGiveUpYota

Dare me.
SILVER Star
Joined
Mar 28, 2011
Messages
6,571
Location
East Hampton, CT
 
I have read a bunch of threads on tach spikes that stay high and most all mention the coil wire to the emissions computer too (@Output Shaft) .... so if someone can clear that up for me, I'd be thrilled too.
 

NeverGiveUpYota

Dare me.
SILVER Star
Joined
Mar 28, 2011
Messages
6,571
Location
East Hampton, CT
 
Ok the upper diagram that OS added, in the facing left side, what the hell are those two electrical components labelled VSV? I ask because I have at least three from memory, possibly more, green clips that are plugged to nothing. (I don't have the front headlight washer res there and hooked up so always figured at least one went to its electrical when installed).
 

gregnash

Anal Retentive Analyst
SILVER Star
Joined
Nov 4, 2011
Messages
11,840
Location
Carson City, NV
 
Got a quick minute last night to test the vacuum switch and tested fine so definitely not that. That was before the rain hit again and by the time it let up it was dark and late.

Surprisingly I was able to find a used ECM on ebay for $20 from Cruiser Junktion, message them to ensure that it was tested good and they responded quickly saying it had come out of a running truck. So done and done.. should be here next week and I will swap them out. @rusty_tlc Looks like you will have a new toy next month!
 
Joined
May 5, 2016
Messages
54
Location
HI
Pulled the Emission board apart to look at the solder points of the connector, found three cracks in the solder. Re-soldered them and so far my ICS is working properly, but time will tell as it was an intermittent problem. Cross referencing my pic with the cracks and @Output Shaft pic of the Emissions manual don't seem to align with the ICS control circuit... unless I'm looking at this wrong...

Emissions Board.JPG
 

Spike Strip

Midnight Rider
SILVER Star
Joined
Nov 22, 2005
Messages
14,796
Location
Lexington
 
 
The cracks would indicate why it was intermittent: When board heats up, cracks expand and lose conductivity.

Anybody who plans to keep the Emissions computer should do this as a precaution. Just be careful not to overheat the board and lift the traces. Just a simple reflow is all you need with a pencil point tip.
 

Landpimp

GOLD Star
Joined
Mar 14, 2003
Messages
16,069
Location
Gig Harbor WA
 
 
 
I have access to the same guy in a vintage hi fi shop right here in my little town, he has down some small non Hi Fi work for me to nothing. We they opened a a few years ago it was like a gift from god...........seeing how I am an old Hi Fi nut ;)

also have an old Ma Bell Telephone guy(grandpa of my guys at the shop).......he can do some amazing things.

Again, you *should* be able to get these repaired for a 100 bux or so if you can find a Vintage Hi-Fi repair shop that is willing to look at it. I gave up in Los Angeles because I don't speak the language of the current crop of repair people... :p

When I was a younger pain-in-the-arse, there used to be a ton of old Lockheed Skunk Works guys around who repaired this kind of stuff on the side (and loved doing it), but they're all gone, now.... :( Used to take all my Vintage Marantz and Mcintosh Hi-Fi stuff to them. But this was before the telegraph was invented, mind you. :rofl:
 

Users Who Are Viewing This Thread (Users: 0, Guests: 1)

Top Bottom