Laptop/USB/ECU problem, quick question

[spudly13]

I know i know its not datsun related, just hoping someone here could possiby give a little insight.

 

My drift car is an e30 with an lt1 out of a 96 firebird formula.

 

I found some software for checking DTCs and live data etc. I wired up the obd2 port and bought an elm327 usb cable.

 

 

So the problem. ecu on, engine off, i can get it to connect and view the trouble codes. But as soon as i start the engine the usb disconnects from the laptop and disappears from "devices and printers", engine off, unplug, plug back in it will reconnect.

 

Any input appreciated!

[flatcat19]

Will it even show when running or not at all?

Unplug and plug back in while running?

[spudly13]

No live data will show up while running, ive tried unplugging and plugging back in while running, it wont connect because the laptop isnt recognizing the usb while the engines running?

 

when the engines off though i can see some certain live data, such as coolant temp, intake air temp, throttle percentage.

[flatcat19]

And you have the pinout for the DLC wired correctly? 

 

I'm trying to find the pinout to follow along. Not having good luck. 

[spudly13]

http://www.lt1swap.com/fuseblock_obd2port.html

 

Edit: scroll to the bottom of that link^^^

 

Yes i "believe" i have it all wired correctly, Someone else mentioned "to much electrical noise" but im not sure what that means.

[spudly13]

And heres the ecu pinouts

 

http://www.lt1swap.com/lt1_pcm_pinout.htm

 

 

Edit: i have pins 4 and 5 grounded, Pin 16 is 12v off ignition switch, and as im looking back over those pinouts i need to go out and verify which other pins im using.

[flatcat19]

Question...Can you read mode 6 on your scanner/laptop?

[flatcat19]

It sounds like something is killing the ignition switch signal when running. Can you verify that?

[spudly13]

while running i have 12 volts at pin 16 off the ignition yes.

 

And the software im trying to use has a tab for mode 6 testing but i cant get it to do much of anything

 

 

Its to dark to try and verify all the pins and getting to late to move it into the shop (dont wanna piss of the neighbors) ill move it in tomorrow and finish checking over my wiring.

 

Also, i just noticed while i tried it again, while running it doesnt just disconnect, it actually disconnects and reconnects erratically but never stays connected for more then a few seconds at a time

[flatcat19]

Maybe not a secure enough connection or one of the outputs on the DLC is running PWM/pulsing. 

[oldskoolvws]

Are the baud rates matching and supporting as I'm guessing your going all serial and not CAN-bus. With engine off, it's only reporting X-data, with engine running it's reporting XXXXX-data. If the baud is too slow or not matching (parity, etc), you can get communication faults. If it's an ignition power fault, typically there will be an undervolt code thrown.

[flatcat19]

Are the baud rates matching and supporting as I'm guessing your going all serial and not CAN-bus. With engine off, it's only reporting X-data, with engine running it's reporting XXXXX-data. If the baud is too slow or not matching (parity, etc), you can get communication faults. If it's an ignition power fault, typically there will be an undervolt code thrown.

 

Good thought. 

[spudly13]

i will try all the different baud rate options, i was told most cheap cables use 38400, and the nicer ones use 115200.   I was trying to use 38400 and havent actually tried any others, yet.

[mhub91]

is the USB cable a data cable? Or just some generic USB charger you found laying around?