Autosport Labs

I was working on configuring my RaceCapture Pro in-vehicle today and had it hooked up to my computer while it was concurrently powered by the vehicle, so I could easily download configuration changes. When I turned off the ignition key I was surprised to see some idiot lights still illuminated on the dash. Measured voltage across the 12V +/- pins of the RaceCapture Pro and saw 3.3V. Promptly disconnected the USB cable from the computer and the voltage dropped to zero and the idiot lights went out.

It's probably not a good thing to be trying to power up the vehicle through the computer's USB port when the ignition is off. Maybe a diode on the 12V power to the RaceCapture Pro could prevent backfeeding to the vehicle in such case?

Yes, it would be good to isolate the USB power line. Thanks for the note!

I noticed this as well, except my car kept running even after removing the key. Of course the next time I tried to start it I got an error saying incorrect sentry key. This is on a Dodge.

Is there anything we can do to fix this? It is causing all kinds of problems in my car with the immobilizer key system.

This is only happening when you are connected via USB, correct?

You could put an IN4004 diode in series with the 12V input to RCP. You can find this diode at RadioShack.

Keep us posted on how that works

Yes, it seems to be a problem if I power the RaceCapture up through USB without the car running.

I will head to RadioShack and see if they have one of those and give it a shot. I'll report back when I get a chance to give it a try.

Note, you will want the Cathode of the diode towards RaceCapture/Pro. Let us know how it works out!

This worked perfectly. No more CELs dealing with the immobilizer key.

Noted. We will be sure to update the next board revision!