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How to send commands to ELM327 OBD interface

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powerampfreak

Jan 1, 1970
0
Hello!
I'm looking for information how to send commands to the popular ELM327 OBD interface. I want to design a stand alone device that check long term fuel trim values along with some other parameters.
Is there a good guide somewhere how those commands are set up?
Thanks in advance
 
M

miso

Jan 1, 1970
0
It looks like the device you buy is just a packaged version of the chip
and a bit of glue electronics. Is the actual datasheet useful?
 
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powerampfreak

Jan 1, 1970
0
Great guys!
ELM327 is a pre-programmed PIC processor. It communicates by RS-232, so probably I can set up another PIC through the USART and communicate with the ELM.
And possibly use a 2x16 char LCD display to show the parameters. Brill !!!
 
M

miso

Jan 1, 1970
0
I wonder if it was defective? Maybe it latched up.

Otherwise, can you just hyperterminal to it and play around?
 
M

miso

Jan 1, 1970
0
Well close. The Infiniti socket is 16 pins and so is standard ODBII. But
this is a 14 to 16 pin adapter.

And I thought only Apple uses GD proprietary connectors.

The shop manual calls the ODBII scanner the GST (general scanner tool),
just to make the manual harder to read I suppose.

BTW, if you never did it, for like $20 or so, there are websites that
let you download the official manuals. I suppose there are pirated
manuals as well, but $20 seems fair considering what cars cost. You get
a one day subscription to the service. it is really intended for repair
shops.
 
J

josephkk

Jan 1, 1970
0
This forum and article might be of some help.
"free OBD2 software with MPG calc"
<http://ecomodder.com/forum/showthread.php/free-obd2-software-mpg-calc-7490.html>

Incidentally, I bought a Mini ELM327 BlueTooth on eBay to play with.
The plan was to leave it plugged into my vehicle OBD2 connector and
have it communicate performance numbers via BT to my Droid X phone
while driving. The plan was ruined when I found myself with a dead
car battery the next morning. It seems that the Mini ELM327 does not
turn off when the ignition key is off, and continues to draw power.
Actually, it drew enough power to get hot enough to partially melt the
blue plastic case. A quick survey of other such devices indicates
similar problems. I had to crack the case to install an on-off
switch.

There is something weird about this, a PIC eating enough power to flatten
a 12 V, 50 Ah or more battery in a few hours??? Hot enough to melt the
case??? Where in hell is all that energy going?

???-)
 
C

Charlie+

Jan 1, 1970
0
There is something weird about this, a PIC eating enough power to flatten
a 12 V, 50 Ah or more battery in a few hours??? Hot enough to melt the
case??? Where in hell is all that energy going?

I have had one of these clone ELM bluetooth units for about a year 1.5
version, no signs at all of overheating, gets slightly warm in use as
you wd expect, I dont leave it plugged in doing nothing though....!
Maybe OP has been unlucky in his units, but it seems to be a known
problem, look on Amazon comments etc.
C+
 
J

josephkk

Jan 1, 1970
0
Well close. The Infiniti socket is 16 pins and so is standard ODBII. But
this is a 14 to 16 pin adapter.

And I thought only Apple uses GD proprietary connectors.

Bwahahahahah. Large companies have been using proprietary connectors
since there were connectors, well over 100 years. How could you possibly
be that naive?
 
J

josephkk

Jan 1, 1970
0
^^^^^



And someone with no knowledge that vehicles DO have "accessory" power
that goes off when the ignition switch is off :)

...Jim Thompson

This is on the OBD2 connector, which does not depend on the ignition
switch position. Please pay attention properly.

?-)
 
L

linnix

Jan 1, 1970
0
I have had one of these clone ELM bluetooth units for about a year 1.5
version, no signs at all of overheating, gets slightly warm in use as
you wd expect, I dont leave it plugged in doing nothing though....!
Maybe OP has been unlucky in his units, but it seems to be a known
problem, look on Amazon comments etc.

It's just bad designs/programmers. Poorly design products can kill any battery. Don't they know about low-power/idle/standby modes? Perhaps they do and will be ready to sell you an upgrade with a premium price.
 
T

tm

Jan 1, 1970
0
Jim Thompson said:
It doesn't? When I get smog-checked, they plug into the OBD2, then
turn the key!!!

...Jim Thompson
--

The 12 volts on the ODB2 connector is directly to the battery. It is on all
the time.
 
L

linnix

Jan 1, 1970
0
message





The 12 volts on the ODB2 connector is directly to the battery. It is on all

the time.

And they know nothing about activity timer? All smartphones are connected to the batteries all the time, but not on all the time.
 
It doesn't?  When I get smog-checked, they plug into the OBD2, then
turn the key!!!

The ECU which they talk to isn't on unless you turn the key

OBD2 connector has KL30, the ECU wake-up/shut-down based on KL15



-Lasse
 
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