The PCM instantaneously determines which gear should be selected by
various signals sent from sensors, and actuates the shift control
solenoid valves A and B to control shifting. Also, a Grade Logic Control
System has been adopted to control shifting in D4 position while the
vehicle is ascending or descending a slope, or reducing speed.
From sensor input signals, the PCM determines whether to turn the
lock-up ON or OFF, and activates lock-up control solenoid valve A and/
or B accordingly. The combination of driving signals to lock-up control
solenoid valves A and B and the linear solenoid pressure is shown in
the table below.
GRADE LOGIC CONTROL SYSTEM
The PCM compares actual driving conditions with driving conditions
memorized in the PCM, based on the input from the vehicle speed
sensor, the throttle position sensor, the barometric pressure sensor,
the engine coolant temperature sensor, the brake switch signal and
the shift lever position signal, to control shifting while a vehicle is
ascending or descending a slope, or reducing speed. Ascending
When the PCM determines that the vehicle is climbing a hill in position,
the system extends the engagement area of 2nd gear and 3rd gear to
prevent the transmission from frequently shifting between 2nd and 3rd
gears, and between 3rd and 4th gears, so the vehicle can run smooth
and have more power when needed. There are two ascending modes
with different 3rd gear driving areas according to the magnitude of a
gradient stored in the PCM.
The PCM memory contains shift schedules between 2nd and 3rd gears,
and between 3rd and 4th gears that enable the PCM’s fuzzy logic to
automatically select the most suitable gear according to the magnitude
of a gradient.
Fuzzy logic is a form of artificial intelligence that lets computers
respond to changing conditions much like a human mind would.
When the PCM determines that the vehicle is going down a hill in
position, the shift-up speed from 3rd to 4th gear when the throttle is
closed becomes faster than the set speed for flat road driving to widen
the 3rd gear driving area. This, in combination with engine braking
from the deceleration lock-up, achieves smooth driving when the
vehicle is descending. There are two descending modes with different
downshift (4 — 3) schedules according to the magnitude of a gradient
stored in the PCM. When the vehicle is in 4th gear, and you are
decelerating on a gradual hill, or when you are applying the brakes on
a steep hill, the transmission will downshift to 3rd gear. When you
accelerate, the transmission will then return to 4th gear.
When the vehicle goes around a corner, and needs to first decelerate
and then accelerate, the PCM sets the data for deceleration control to
reduce the number of times the transmission shifts. When the vehicle
is decelerating from speeds above 26 mph (41 km/h), the PCM shifts
the transmission from 4th to 2nd earlier than normal to cope with
This book is based on the «Automotive Transmission Troubleshooter» software by the
same author. All similarities to this software package are intended. Both of these
products are copyrighted by the author, Mandy Concepcion. For further insight on
automotive transmissions please see our complementary DVD-Video.
Section: Acura/Honda Transmission Oil Pan (ID) Identification
Honda/Acura transmissions don’t have a transmission oil pan. They
mostly carry the shift solenoids on the outside of the transmission. For
this reason an oil pan is not needed. To get to the valve body the
transmission has to be opened or halved completely. To help you
identify the transmission here you can reference the different diagrams
that have been extracted from actual photographs from the author’s