Code 700 in the engine computer just means there is a diagnostic fault code memorized in the transmission computer. The minute you unplugged that computer, you erased all the valuable information it had in its memory. Fortunately the code(s) came back so your mechanic can read it. When the computer detects a problem with a sensor or slippage in the clutch packs, it defaults to "limp-in" mode where it stays in second gear. That is to allow you to drive it slowly to the repair shop, not on the highway.
The only way to reset the computer is to turn the ignition switch off, then restart the engine. If it starts out right away in second gear, suspect a sensor problem has been detected. If it starts out in first gear like normal, then goes into second gear after one or more upshifts, the computer likely detected internal slippage, but the fault code will tell for sure.
Monday, February 15th, 2010 AT 4:55 AM