If the engine controller is found to be faulty, repairs would take longer and the launching could slip further, probably to early next week.

The mission was postponed again about five hours before liftoff on 24 July due to a faulty main engine controller on the number three main engine.

The faulty engine controller, valued at $4 million, was on the shuttle's third main engine.

In addition, a short circuit cut power to an engine controller; engineers would later attribute this to serious wiring problems that grounded the entire shuttle fleet for months.

The engine controller regulates the functions of the two independent fuel and oxidizer circuits.

These valves are positioned by the engine controller, which uses them to throttle the flow of liquid oxygen to the preburners and, thus, control engine thrust.

The engine controller regulates the amount of gaseous hydrogen allowed to bypass the nozzle coolant loop, thus controlling its temperature.

The injectors are activated using one of two methods - hydraulic pressure from the fuel pump, or an electronic signal from an engine controller.

Products include engine controllers and custom software for UAV's.

The wiring inspection was ordered after a short circuit on the Columbia caused two engine controllers to shut down on a flight in July 1999.