Caddy STS w/ 555U and serv. theft light

what year?  i went through techsoft and didnt find any install notes on it.  they might have not powered up an accy wire or ign wire.  or powered it up as the wrong one.  i do know that some cars like a saturn sl1 (or something) needs to have an accy see (-) during remote start to prevent the check engine light, something along those lines.

I am not familiar with the 555, but I might know what is wrong. You need to do two things. First, hook up the vehicle's key in sense wire to your remote starter's ground out when running wire. Be sure to diode isolate this line if you are using it for something else. This will trick the car into thinking it has a key in the ignition. Secondly, you must use a relay to open the pink ignition wire to the factory theft module usually located above the gas pedal. This relay should be powered by ignition and a diode isolated ground out when running line. This will prevent the car from looking for a valid transponder key in the ignition cylinder while remote started. Hope this helps.sparky

Thaks for that info.  Do you know what the key sense wire is? (color).