Method for operating a vehicle security system including code comparison after starting which counts start attempts

A method for operating a security system for an automotive vehicle having an engine including engine running electrical components and an electronic engine controller, said automotive vehicle including a lock switch having a selected position providing power to said engine running electrical components to run said engine, said lock switch being movable by a key having a predetermined cut, said key further containing a first security code stored electronically, said electronic engine controller comprising a counter for counting an attempted start count, said security system having a theft control module operatively connected between said electronic engine controller and said lock switch, said theft control module having a memory storing a second security code and having means for communicating with said key to retrieve said first security code, said method comprising the steps of:

• using said key to place said lock switch in said selected position;
• comparing said attempted start count to a predetermined number;
• disabling said engine from running if said attempted start count exceeds said predetermined number, otherwise enabling starting of said engine;
• incrementing said attempted start count;
• operating said theft control module to interrogate said key for said first security code;
• receiving said first security code into said theft control module;
• comparing said first security code with said second security code;
• if said first security code does not equal said second security code, then disabling said power to said running electrical components and setting said attempted start count to be greater than or equal to said predetermined number;
• if said first security code equals said second security code, then:
• signaling said electronic engine controller of said equality;
• generating a challenge code in said electronic engine controller;
• transmitting said challenge code to said theft control module;
• calculating a response code in said theft control module based on a secret algorithm operating on said challenge code;
• transmitting said response code to said electronic engine controller;
• receiving said response code in said electronic engine controller;
• calculating a comparison code in said electronic engine controller based on said secret algorithm;
• comparing said response code to said comparison code;
• if said comparison code equals said response code then resetting said attempted start count and supplying power to said engine running electrical components;
• if said comparison code does not equal said response code then disabling said power to said running electrical components and setting said attempted start count to be greater than or equal to said predetermined number;
• and
• if no response code is received within a predetermined time then disabling said power to said running electrical components.