Scanmaster and laptop question

Correct me if I'm wrong, but my understanding is that you can't scan or tune an OBD1 LT1 if a scanmaster is hardwired to the car because both use a two way signal to the PCM. I have a scanmaster mounted in my air vent and I just received my ALDL cable in the mail. I plan on starting the tuning process soon with Tunercats. Could I just mount a switch to the power wire for the scanmaster and turn it off while tuning/logging or should it be to the data wire? I'm trying to get everything squared away before I start tuning.

Correct me if I'm wrong, but my understanding is that you can't scan or tune an OBD1 LT1 if a scanmaster is hardwired to the car because both use a two way signal to the PCM. I have a scanmaster mounted in my air vent and I just received my ALDL cable in the mail. I plan on starting the tuning process soon with Tunercats. Could I just mount a switch to the power wire for the scanmaster and turn it off while tuning/logging or should it be to the data wire? I'm trying to get everything squared away before I start tuning.

I have no personal experience with this device, but if it is putting the ALDL channel into a special mode then you could run into problems using it with other devices that also set special modes (like datamaster or tunercat).

OTOH if it just passively reads the data that is already on the wire, then it shouldn't be a problem, assuming the device is reasonably well-designed.

Just cutting power to it should be sufficient.

I'd switch pin 9, the data wire.

I'd switch pin 9, the data wire.


Yup, put a small switch on the data wire. Scanmaster turns off if no signal is received.

I just did this Scanmaster install on my TA, hardwired it, then thought hmmm.. what happens if Laptop connects at same time, so I fired up Datakaster and when I hit "connect" it would not connect then the laptop screen started freaking out, the icons were blinking and programs started launching, hard to explain but seemed like the mouse was flying all over and launching programs at random.

I drilled a small hole in the scanmaster case and installed a toggle which opens up the data wire. No problems since.

BTW, I installed my Scanmaster under the "visor" which blocks sun from hitting the speedo... hidden and can still see all the gauges.

From my online ScanMaster guide:
You need to provide for a "disconnect" on the white data wire. It must be disconnected if you attempt to attach any other device to the ALDL connector, like a laptop cable for LT1_Edit or other programming system, a cable for a Hypertech Power Programmer, or a dealer scan tool. The ScanMaster uses bi-directional communication, and the signals from the ScanMaster will interfere with the signals from the programmers or scanners. A small switch or a "plug" will suffice.

I located a miniature switch right next to the ALDL connector.

Son of a... I thought I read that somewhere but I couldn't remember/find the source. Thanks!

My website moved a few months back, so any old links may not work:

http://www.injuneer.com/ScanMast.html

http://www.injuneer.com/images/photos/Interior/DCP04287a.jpg