Alarm Installer, Need Your HELP!

To any alarm installer expert, I just need an input or possibly an answer. I own a 1991 Honda Accord SE and experiencing a problem. Can an alarm installation process (professionally done) possibly screw up my instrument panel wiring? I'm currently experiencing this flashing "S" on my instrument panel and my speedometer reads "O" RPM at any speed, then eventually the engine light follows. The car always starts off normal then it will happen and it comes and goes from then on, sometimes for a prolong period of time. The steady "S", normally, is an indication when sports option is engaged on my automatic shifter. I'm just wondering if it has any relation to the newly added alarm system to the car. It just started happening right after the day the alarm was installed. I appreciate any input.

this is happening because your speedometer cable is broken. After you get driving, the ECU looks for an output from your speedometer - and when it gets none, it activates the check engine light. Either they forgot to reconnect it or it's just a coincidence