99 5.7L EFI OBD question

[GaryDoug]

You can use an RS232 cable but you would have to add a small circuit to the output. It's called the "two transistor" mod and it inverts the signals as well as stepping the levels up and down as needed to work with the TTL (5v) levels. Before FTDI started making the converter chips, that is what we had to do to use it with the GM ecu's.

http://freecircuitdiagram.com/2009/0...ng-transistor/



If you want to buy a cable, this one is slightly cheaper than the ones at FTDI:
https://www.amazon.com/GearMo%C2%AE-.../dp/B004LC28G2

If you want one from FTDI, get this one:
https://shop.clickandbuild.com/cnb/s...CategoryID=296

Be aware that neither comes with the 10-pin OBD connector.

 

[GaryDoug]

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[GaryDoug]

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[alldodge]

Sounding like some real good work. Once you get it all worked out I would like a copy to check out

 

[thumpar]

I would like a copy also. What is the pinout for the connector?

 

[GaryDoug]

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[GaryDoug]

Follow-up just for once post: For what it is worth, I fixed the problem with the app that I bought. I just needed to completely silence the ecu from sending out housekeeping date to the bus. Adding a simple "repeat 3 times" to the Silence routine stopped the jumping around. Nothing to do with any electrical disturbances, just bad software. I finished the app I was intending to write and it does three times as much as the bought app and it's free. Too bad I can't give it to you because it is in a Mediafire account too, haha. Other forums are interested though. Bye.