Hoping someone can help me with some troubleshooting. Just got the USB to serial adapter last Friday and built my harness and tried it out over the weekend with mostly failed results.
Here's the exact one I bought:
http://www.ebay.com/itm/360871019374?_trksid=p2060353.m2749.l2649&ssPageNa me=STRK%3AMEBIDX%3AIT
I followed the simple instructions from the original post on this thread, used no diodes or resistors, just connected the Tx and Dx together and plugged that into my 8192 terminal (terminal "M" on my OBD1 12 pin port) and the ground to the ground terminal (terminal "A").
Real quick, the car I'm working on is my 1994 Cadillac Fleetwood w/ LT1.
When the FT232RL chip is plugged into just the car, both the tx and dx leds light up constantly with the car on (actually they appear to blink rapidly, but fast enough that they appear to be solid on).
If I'm plugged into the laptop via USB the lights will blink when it's first plugged in and being recognized, and if I try to connect to it from any software. However if I connect it to both the car and the laptop, it mostly ceases to function.
So let's run down quick what I've done so far: I've tried 3 different USB cables, I've tried 2 different laptops running on a different OS (my current laptop running 64-bit Win7 and my old laptop running 32-bit WinXP), I've tried several different versions of the driver, I've built two different harnesses (my first was kind of weak sauce, just threw it together quick with stuff I had laying around so I could test it out first, I then built a second one with better wire and soldered all my connections to rule out that as the culprit) and I've tried several different tuning programs.
I believe I have the correct files, I got my $EE file from, I can't remember now, it wasn't on here because I hadn't signed up for an account yet, possibly from the TunerPro website, but I may try downloading a different definition file from this site just to rule that out. I've attempted to connect using TunerPro RT, TunerCATS RT and Datamaster. TunerPro RT will recognize the adapter if it's not connected to the car once I select the correct COM and will pass the test every time. But once I connect to the car and attempt to acquire data, it insta-fails every time.
TunerCATS RT has yet to have any luck connecting to it, but I've messed with that program the least so I'm not confident I'm doing it correctly on there. Datamaster seems to work until I actually try to record data. It will pass the test, or at least it was until last night. Now I get an unknown error when I test it, but that may be a driver issue. One of the last times I plugged it back into the laptop and it was being recognized it identified it as a Microsoft serial mouse and loaded new drivers for it, so I think I need to go back and wipe out all the drivers and try installing those again after a reboot. BTW, I'm primarily working from the old XP laptop since that one is smaller and easier to setup inside the car.
Before I developed that issue though I was able to record data and have several sessions recorded both from the engine and trans and alternating between both, but during every session it would lose communication, wait for a few seconds and then re-establish the connection, work for a few seconds and then drop out again. And while some of the data it collected appears to be perfectly accurate such as RPMs and engine temps, other data is completely whack. When reviewing the one session where I actually drove around for a bit, there were times when my reported speed (in MPH) would jump to well over 100. Since I was driving in town on 25-35 mph speed limit streets, I wasn't going anywhere close to 100 or above.
I also noticed there's a window in Datamaster that monitors DTCs, and it was randomly lighting up like a christmas tree and mostly didn't make any sense to me. I do get a couple recurring trouble codes, one from a steering sensor and one for interior lighting I think, I'd have to pull those from the HVAC unit to see which ones they are, but I've never put much effort into tracking them down since the car functions perfectly. No SES lights or any idiot lights ever come on and the only real problem it's ever had was when it dropped an O2 sensor last year which I replaced. I haven't replaced the other side yet cause they're kind of a pain in the butt to get out being a 20+ year old car with 130k miles on it and pretty much still 100% of it's original equipment still on it, things like that are a little rusty and little stubborn to remove. But it's on the agenda now that spring is coming.
If anyone is interested, I can upload the sessions I saved from Datamaster and see if anything in there makes any sense or could point you in the direction of where my problems are originating from. But at this point it's just driving me nuts. One other thing I just remembered, it seems that whenever I'm plugged into both the laptop and the car, the LEDs will blink some for a little bit, but shortly after they go dark, which doesn't make sense if it's receiving data from the PCM, but as soon as I unplug the USB from the laptop, they light right back up. Maybe I just got a bad adapter? I don't really know how to check for that, but if anyone has any ideas, I'm all ears.
If I missed any important info, ask and I'll provide what I can. I also have pictures of my adapter and the cable I made if anyone wants to rule those out as my culprit. Or maybe I'm just missing something simple and obvious, I'm experienced with the mechanical side of cars, and I'm even pretty good with electronics and computers, but engine tuning is well outside my normal wheelhouse so I freely admit to being a complete noob as far as that is concerned. I just remembered that at one point I even grabbed my phone and filmed datamaster for a few seconds so if anyone wants to see that I can upload it as well, because while I'm not up to snuff on the tuning stuff yet, what I was seeing on the screen while it was recording really seemed strange.
I think that's enough rambling for the moment, again any ideas, questions, let me know. And if anyone wants pics, video or the datalogs I saved say so and I'll copy them over to this laptop and upload them.
Thank you for any and all help.
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