Trying to communicate with 1226865 ECM

American Delco GM ECUs and PCMs, ALDL, OBD 1.5.
User avatar
Posts: 304
Joined: Sun Jan 25, 2015 4:21 pm
Location: Sydney

Re: Trying to communicate with 1226865 ECM

Postby j_ds_au » Fri Sep 27, 2019 4:14 am

ndndndnd wrote:Do I need another transistor circuit to invert the signal? I thought the 'Q1' transistor (2N3904) in the WinALDL circuit already inverted the signal? I was investigating inverting the signal so I could omit the transistor circuit and reduce the number of variables...

I guess what I'm getting down to is: does anyone know if this circuit should be working, even through the FT232BL chip?

Thanks for your continuing help guys!

ND

The purpose of the existing transistor is as a buffer and level converter. The fact that it also inverts is a nuisance in this case.

The circuit is fine (indeed, looks quite good) if you're driving an FT232RL, because you can enable a further inversion within the chip. But it cannot work with an FT232BL without an extra transistor (and two 10k resistors) to correct the signal polarity.

Joe.

Posts: 17
Joined: Thu Sep 12, 2019 7:40 pm

Re: Trying to communicate with 1226865 ECM

Postby ndndndnd » Sun Sep 29, 2019 8:32 am

Ah, ok. This almost sounds like progress!

So, ummm, how do I wire in the extra transistor and where do the extra two 10k resistors go? Can I just use another 2N3904?

Thanks!

ND

User avatar
Posts: 304
Joined: Sun Jan 25, 2015 4:21 pm
Location: Sydney

Re: Trying to communicate with 1226865 ECM

Postby j_ds_au » Mon Sep 30, 2019 4:29 am

ndndndnd wrote:Ah, ok. This almost sounds like progress!

So, ummm, how do I wire in the extra transistor and where do the extra two 10k resistors go? Can I just use another 2N3904?

Thanks!

ND

Hi ND,

Yes, a 2N3904 is fine. Ground the emitter; connect one resistor in series with the base, the other end connecting to the collector of the first transistor (disconnect the FT232BL); connect the other resistor as a pull-up to +5V for the collector, which then feeds the FT232BL.

Joe.

Posts: 17
Joined: Thu Sep 12, 2019 7:40 pm

Re: Trying to communicate with 1226865 ECM

Postby ndndndnd » Tue Apr 28, 2020 8:16 am

Yayy! I've actually managed to make this work!

Ok, I revisited this when I planned to tune up my carb, got out my analogue multimeter/dwell meter and found it dead. Replacements are hard to come by/expensive/old so I thought I'd look into reading data from the ALCL and seeing if I can tune the MCS through that.

After re-reading my threads and picking up where I'd got to (really handy way of recording what on earth you were doing!) I thought I'd try to buy the read-deal FT232RL, rather than a clearly-fake eBay special.

A bit eccentric in the days of the internet, but I called the FTDI technical line for some advice, and they were really helpful!

I was advised to buy one of these:

https://ftdi-uk.shop/collections/usb...we-1800-bt_0-0

The advantage of the RS232 cable is that it contains and FT232RQ chip, plus a level shifter. This means it can cope with Voltages up to 15V, quite handy when your ALCL is pumping out data at battery voltage.

I simply plugged it into FT_PROG and inverted the RxD (received data) input and then went out to the car.

10k ohm resistor between pins A & B, connect GND (black wire) to pin A and RxD (yellow wire) to Pin D, fire up WinALDL, select 4800 baud and the 'CLCC car 1984, 1985, 1986' configuration. Key on.... and data simply started flowing.

After all that pissing about it was dead easy in the end - I just had to buy the right fricking cable in the first place!

My problem now is making the data usable.

Can anyone confirm what changes ALDL mode makes with the 1226865 ECM? I think it's advancing the timing, and possibly forcing it into closed loop. Does anybody know how to stop it doing this, so I can analyse the car when it's running normally?

User avatar
Posts: 5260
Joined: Sat Feb 28, 2009 8:38 pm
Location: Wellington NZ

Re: Trying to communicate with 1226865 ECM

Postby delcowizzid » Tue Apr 28, 2020 10:41 am

Normally sets spark advance to the value in diagnostic advance setting in the ecu. On the holden it locks at 10 degrees upto a certain rpm like 2500 then returns to normal advance both commanded advance and rpm settings are adjustable
If Its Got Gas Or Ass Count Me In.if it cant be fixed with a hammer you have an electrical problem

Posts: 164
Joined: Mon Mar 09, 2020 4:35 pm

Re: Trying to communicate with 1226865 ECM

Postby In-Tech » Tue Apr 28, 2020 12:11 pm

ndndndnd wrote:Yayy! I've actually managed to make this work!

https://ftdi-uk.shop/collections/usb...we-1800-bt_0-0


Hello, just a quick note that your link above didn't work. Here are two that do.
https://ftdi-uk.shop/collections/usb-ca ... 800-bt_0-0 <<<<<<<< for UK
https://ftdi-us.shop/collections/usb-rs ... 800-bt_0-0 <<<<<<<< for US

What did you use to invert the signal? Is it in your software? Is that what the FT_Prog is used for? :lol: I used to use a 7407 flip flop chip on my rs232 stuff back in the day of making my own crap.

Posts: 17
Joined: Thu Sep 12, 2019 7:40 pm

Re: Trying to communicate with 1226865 ECM

Postby ndndndnd » Tue Apr 28, 2020 5:29 pm

delcowizzid wrote:Normally sets spark advance to the value in diagnostic advance setting in the ecu. On the holden it locks at 10 degrees upto a certain rpm like 2500 then returns to normal advance both commanded advance and rpm settings are adjustable


That's interesting. I am worried that running the engine with the diagnostic mode engaged might cause donation, however if it reverts to the correct advance above a certain rpm that might be safer. When I next go out to the car, I might try the spark advance tables in TunerPro and see if they reveal what's actually happening.

One issue is that the early ECMs like mine can't be reprogrammed via the ALDL port, which makes things more complicated...

Posts: 17
Joined: Thu Sep 12, 2019 7:40 pm

Re: Trying to communicate with 1226865 ECM

Postby ndndndnd » Tue Apr 28, 2020 5:32 pm

In-Tech wrote:What did you use to invert the signal? Is it in your software? Is that what the FT_Prog is used for? :lol: I used to use a 7407 flip flop chip on my rs232 stuff back in the day of making my own crap.


Yes, I just used FT_prog - it was actually fairly straightforward! I'll give a quick summary of the steps used when I get back to my computer.

User avatar
Posts: 5260
Joined: Sat Feb 28, 2009 8:38 pm
Location: Wellington NZ

Re: Trying to communicate with 1226865 ECM

Postby delcowizzid » Tue Apr 28, 2020 6:21 pm

It locks timing at 10 degrees or whatever I'd set at o that you can check base timing with a light. Do you have a bin and xdf
If Its Got Gas Or Ass Count Me In.if it cant be fixed with a hammer you have an electrical problem

Posts: 17
Joined: Thu Sep 12, 2019 7:40 pm

Re: Trying to communicate with 1226865 ECM

Postby ndndndnd » Tue Apr 28, 2020 7:23 pm

I have the TunerPro files for the 1228079 ECM, which I think was used for the later 87-88 CCC Camaro and others. I've not yet tried it to see if it will work with the earlier 1226865. Theoretically it should interpret some data correctly, and some data may be junk...

Previous

Return to US ALDL ECUs

Who is online

Users browsing this forum: No registered users and 1 guest