Grade Logic Control System

WARNING: This page is about a different car, the 1998 Honda Odyssey, 1998 Honda Accord, and 1998 Acura 2.3CL. However, it is still accessible from the selected car via links, so may be relevant.

The PCM compares actual driving conditions with driving conditions memorized in the PCM, based on input signals from countershaft speed sensor, Throttle Position (TP) sensor, Engine Coolant Temperature (ECT) sensor, brakelight switch signal and A/T gear position switch. The PCM uses these input signals to control shifting while vehicle is ascending or descending a slope, or during deceleration.

When the PCM determines vehicle is ascending a slope with shift lever in "D4" position, PCM extends engagement of 3rd gear to prevent transaxle from frequently shifting between 3rd and 4th gears. Shift points between 3rd and 4th gear are stored in PCM, which allows the most suitable gear selection depending on conditions.

When the PCM determines vehicle is descending a slope with shift lever in "D4" position, PCM changes upshift speed from 3rd to 4th gear when throttle is fully closed. This widens the 3rd gear operating range from that programmed for level surface operation and, in conjunction with engine braking from torque converter lock-up, provides smooth vehicle operation. When vehicle is decelerating on a gradual hill in 4th gear, or when applying brakes on a steep hill, the transaxle will downshift to 3rd gear. When vehicle accelerates, transaxle will upshift into 4th gear.

When vehicle decelerates from speeds greater than 30 MPH, PCM shifts transaxle from 4th gear to 2nd gear earlier than normal to reduce the number of times transaxle shifts. This allows smoother acceleration and vehicle operation.