Modern automatic transmissions use pressurized hydraulic fluid to change gears. Every time a gear change is required, the car’s computer activates a transmission solenoid, which directs transmission fluid into the valve body to engage the correct gear.. Description. The versatile MicroSquirt with 30″ Harness: Standalone Engine Management System, Transmission Controller or CAN I/O Expansion Module- Version 3.0 MicroSquirt with 30″ Harness is an entry-level, fully assembled ECU and universal 30″ pigtail with varied applications targeting power sports, single cylinder all the way up to 8 cylinders with up to 2 fuel and 4 spark outputs.. This is the warning message you will see when there is a fault with the automatic transmission. FAIL SAFE means the transmission is in limp mode, in limp mode you only have one gear and no torque converter lock up..