Uber-easy DIY USB ALDL Cable

[RobertISaar]

with the one i posted:

connect the RXD and TXD pins together(solder would be my method), then connect that circuit to the ALDL pin M, then connect the ground pin on the converter to the ground pin in the ALDL connector (pin A).

it's that simple.

[one92rs]

i will get a buddy of mine to look at this tomorrow. he is all about electric. he is trying to set up a miata with a/c drive motors right now. thanks buddy.

[EagleMark]

with the one i posted:

connect the RXD and TXD pins together(solder would be my method), then connect that circuit to the ALDL pin M, then connect the ground pin on the converter to the ground pin in the ALDL connector (pin A).

it's that simple.

To easy! Does it work? Still to easy... and to cheap...

[RobertISaar]

i've been using it to troubleshoot my testbench. i seem to get quite a few packet errors on the bench if i don't have my 4K PPM signal hooked up to anything though. if i either connect it to a spare cluster or directly to ground, problem goes away ~99%.

however, when i had it hooked up in-car, i had 0 packet errors, so it must be something about the bench causing it.

[phonedawgz]

USB to ALDL 160 Baud Pin E or 8192 Baud Pin M cable for $55 shipped -

http://www.reddevilriver.com/aldl.html

It does use the FT232RL chip

By the time you do $10-15 for the FT232RT USB, 20.90 for the OBD1 ALDL cable shipped, $5 for the box you are at $40. The pre-built cable is $50 + $5 shipping.

[RobertISaar]

i have a cheaper source for the male connector... ~$9 shipped.

combine that with the $9 for the converter and the $3 it costs for a box, that's just over $20 complete.

[FSJ Guy]

Plus, you really don't NEED a cable connector. You can wire it directly to the harness or use flat connectors to connect to the ALDL port. No fancy connector required.

I still haven't had time to test the one I bought from sparkfun yet.

[RobertISaar]

at this price, you can honestly install them permanantly and not feel too bad about it. $12 for a USB cable instead of an ALDL port.

[belaw]

with the one i posted:

connect the RXD and TXD pins together(solder would be my method), then connect that circuit to the ALDL pin M, then connect the ground pin on the converter to the ground pin in the ALDL connector (pin A).

it's that simple.

What do you do with pin B on the ALDL connector?

[phonedawgz]

Earlier OBD1 vehicles need a 10K resistor between pins A and B to start the data flow.

Later OBD1 use bi-directional data flow on pin M and don't require it. Having the 10K resistor between pins A & B won't hurt however.

[89S10_Project]

Earlier OBD1 vehicles need a 10K resistor between pins A and B to start the data flow.

Later OBD1 use bi-directional data flow on pin M and don't require it. Having the 10K resistor between pins A & B won't hurt however.

Is it possible that my 1989 S10 needs this 10K resistor present and that's why I'm not getting data?

[RobertISaar]

depends on the application. most cars don't need it, the some that do tend to need a 10K resistor connected from the B pin to the A pin(or the ground on the converter) either temporarily or permanantly.

if you use a male OBD1 connector, then you could simply run a wire from the B pin to a rocker/toggle switch, then to a 10K resistor, then to the ground circuit. you can then hide all of it in a small project box from radioshack. i think i use the 3" X 2" X 1" versions.

Having the 10K resistor between pins A & B won't hurt however.

depends. some applications go into "ALDL mode" and will change the idle speed and add up to 10* of spark advance.

[belaw]

depends on the application. most cars don't need it, the some that do tend to need a 10K resistor connected from the B pin to the A pin(or the ground on the converter) either temporarily or permanantly.

if you use a male OBD1 connector, then you could simply run a wire from the B pin to a rocker/toggle switch, then to a 10K resistor, then to the ground circuit. you can then hide all of it in a small project box from radioshack. i think i use the 3" X 2" X 1" versions.



depends. some applications go into "ALDL mode" and will change the idle speed and add up to 10* of spark advance.

This is for a '7427 PCM and I will probably omit the ALDL connector for a permanent install. So can I just de-pin the white/black wire that terminates at pin B from the PCM and pitch it?

[RobertISaar]

IIRC, the only thing the 7427 uses the ALDL pin B is for blinking out codes if connected directly to ground.

i'm not a 7427 expert though.

[EagleMark]

This 10K needed for 160 Baud ECM is a horrible rumor created on internet that won't go away! Even the Moates website shows 10k resistor needed for all 160 Baud ECMs. 10K really messes up good data on 1227747 and other old 160 Baud ECMs by putting the ECM in ALDL mode, it increases idle and adds timing, not needed at all for data!

Other then checking codes by crossing A and B I've had no use for 10K, it is needed in $6E to start data flowing. I have no idea what else it is used for except to screw up data.