What happens if you are driving a vehicle with an ATEC/CEC transmission in fourth range and electrical power to the transmission TCU is lost?

What happens if you are driving a vehicle with an ATEC/CEC transmission in fourth range and electrical power to the transmission TCU is lost?

• A. The transmission immediately shifts to neutral.
• B. The transmission will shift to the next lower range (third).
• C. The transmission will remain in fourth range until the vehicle is shut off.
• D. The transmission downshifts until it reaches first range.

Answer: (C)

Shifts in this transmission are controlled electronically by the TCU; when power to the TCU is lost, there are no commands to move the gear range, so the hydraulics hold the last engaged range. If you were in fourth range when the power failed, the transmission will stay in that range because it cannot downshift or shift to neutral without TCU control. The only way to reset or reenable proper shifting is to restore electrical power, which is typically accomplished by turning the engine off and back on or supplying power again; until then it remains in the current range.

Shifts in this transmission are controlled electronically by the TCU; when power to the TCU is lost, there are no commands to move the gear range, so the hydraulics hold the last engaged range. If you were in fourth range when the power failed, the transmission will stay in that range because it cannot downshift or shift to neutral without TCU control. The only way to reset or reenable proper shifting is to restore electrical power, which is typically accomplished by turning the engine off and back on or supplying power again; until then it remains in the current range.