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Thread: LT1 swap into old truck, OBD1 computer on OBD2 harness, repin?

  1. #1
    Carb and Points!
    Join Date
    Feb 2015

    LT1 swap into old truck, OBD1 computer on OBD2 harness, repin?

    (yes, this is a bit long...I've been researching this quite a bit, and wanted to make sure all my bases were covered before I threw my hands up in despair :D)

    Some time ago, I broke the chassis on a '96 Camaro, scrapped the car, and saved the engine and entire wiring harness/ECM to swap into my '62 International Scout 80. I reused the OEM engine harness from the '96, and integrated it into the existing Painless harness in the Scout. I stripped the mating connectors for the engine harness from the rest of the Camaro chassis harness, and removed the bits I wouldn't be using (A/C connections, VATS, BCM, etc). I also did the same with the underhood fuse/relay box. All pink wires I ran to switched power, and orange & red wires to battery power. I installed the 16 OBD2 style connector under the dash, and connected the wires to the same color wires coming off of C220 and C230.

    I have two different 16188051 ECMs that were functional in the Camaro before I tore it down (fried the stock OBD2 computer with a bad HyperTech flash, and the first 8051 I got was for an auto trans car, whereas I was running a manual..needless to say, it didn't run well, lol), and the 16185051 that I was running most recently in the car is the one I'm attempting to use now.

    I used this USB - TTL converter to make a programming cable -, and used these directions to make the cable - I used the FTDI VCP drivers, and connected the RX & TX pins together with a wire to the OBD connector, except for the tan wire, which I wasn't sure if I was supposed to connector the programming cable to the tan or the purple wire. I still have the tan wire on C105 underhood. From what I've been reading, I think I'm supposed to be on the tan wire, with the purple wire being the newer OBD2 bus communication wire that handles things like communication from the BCM.

    I have an XP laptop that I loaded up with TunerPro, TunerPro RT, WinFlash, Datamaster and the Datamaster ALDL check program. The USB converter passes the ALDL cable check with the Datamaster ALDL check program whether I connect to the purple wire or tan wire.

    However, using the WinFlash program, I can't get it to read the vehicle info or the BIN, regardless if I connect to the purple wire or tan wire. Using TTS Datamaster, the program says that it's getting something from the ECM, but it's not valid data. On the USB-TTL converter, I have tried running it with the diode and resistor connected just like the video said, with the wire connected directly to TX/RX without the resistor and diode, and with just the resistor on the RX time, but direct to the TX line. I have also tried with the ground connected straight to battery (which didn't work at all
    ), with the ground connected to just the black wire on the OBD port, with the ground connected just to the black/white wire on the OBD connector - both resulted in the same receiving invalid data.

    Now I'm at a loss....I did see on another thread that the pinouts between the 94/95 and 96/97 at the ECM are slightly I need to connect to a different wire at the PCM since I'm using a '94/'95 computer on a '96 harness? Is it possible that the OSEPP USB-TTL converter just isn't the right one I need? It did just now occur to me that I didn't yet verify that all the power and ground connections to the ECM (I may have forgotten a couple ground on the engine harness), and I'll check those tonight, but I still wanted to make sure I wasn't missing something else.

  2. #2
    Carb and Points!
    Join Date
    Feb 2015
    Solved it on my own...just built another MAX232 based serial cable, as my programming laptop has a real serial port already on it, and all is well now - just downloaded the stock BIN a few minutes ago :)

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