Electronic Control System

Electronic Control System

Electronic Control

The electronic control system consists of the powertrain control module (PCM), sensors, and seven solenoid valves. Shifting and lock-up are electronically controlled for comfortable driving under all conditions.

The PCM receives input signals from the sensors, switches, and other control units, processes data, and outputs signals for the engine control system and A/T control system. The A/T control system includes shift control, grade logic control, clutch pressure control, and lock-up control. The PCM switches the shift solenoid valves and the A/T clutch pressure control solenoid valves to control shifting transmission gears and lock-up torque converter clutch.





Shift Control

The PCM instantly determines which gear should be selected by various signals sent from sensors and switches, and it actuates shift solenoid valves A, B, C, and D to control gear selection.

Shift solenoid valves are a normally closed type. Shift solenoid valve opens the port of shift solenoid valve pressure leading to shift valves while shift solenoid valve is turned ON by the PCM, and closes the port when shift solenoid valve is OFF.

The combination of driving signals to shift solenoid valves A, B, C, and D and their respective gear position are shown in the table.





Shift Control - Grade Logic Control

The grade logic control system is used to control shifting in D, D3 (seven-position transmission), and S with automatic shift mode (five-position transmission). To control shifting while the vehicle is ascending or descending a slope, the PCM compares actual driving conditions with memorized driving conditions, based on the input from the accelerator pedal position sensor, the throttle position sensor, the engine coolant temperature sensor, the barometric pressure sensor, the brake pedal position switch signal, and the shift lever position signal.





Grade Logic Control: Ascending Control

When the PCM determines that the vehicle is climbing a hill in D, D3 (seven-position transmission), and S with automatic shift mode (five-position transmission), the system extends the engagement area of 2nd gear, 3rd gear, and 4th gear to prevent the transmission from frequently shifting between 2nd and 3rd gears, between 3rd and 4th gears, and between 4th and 5th gears, so the vehicle can run smoothly and have more power when needed.

NOTE: Shift commands stored in the PCM between 2nd and 3rd gears, between 3rd and 4th gears, and between 4th and 5th gears, enable the PCM to automatically select the most suitable gear according to the magnitude of a gradient.





Grade Logic Control: Descending Control

When the PCM determines that the vehicle is going down a hill in D, D3 (seven-position transmission), and S with automatic shift mode (five-position transmission), the shift-up speed from 4th to 5th gear, 3rd to 4th gear, and from 2nd to 3rd (when the throttle is closed) becomes faster than the set speed for flat road driving to extend the 4th gear, 3rd gear, and 2nd gear engagement areas. This, in combination with engine braking from the deceleration lock-up, achieves smooth driving when the vehicle is descending. There are three descending modes with different 4th gear driving areas, 3rd gear driving areas and 2nd gear driving areas according to the magnitude of a gradient stored in the PCM. When the vehicle is in 5th or 4th gear and you are decelerating while applying the brakes on a steep hill, the transmission downshifts; to a lower gear. When you accelerate, the transmission then returns to a higher gear.





Shift Control - Manual Shift Mode

The Fit five-position transmission is provided with a D-paddle shift mode in D, and with a sequential shift mode in S. Both modes are entered by pulling the upshift paddle shifter (+; upshift switch) or downshift paddle shifter downshift switch) while driving.

D-Paddle Shift Mode

When the transmission is switched into the D-paddle shift mode by pulling the paddle shifters while driving in D, the transmission can shift into a lower gear by pulling the downshift paddle shifter, and it can shift into a higher gear by pulling the upshift paddle shifter. When the transmission shifts into a lower gear or a higher gear by pulling the paddle shifters, the shift indicator in the gauge control module displays the number of currently-selected gear. This number of the gear goes off when the transmission downshifts automatically, or when the transmission upshifts automatically while coasting.

The transmission stays in 5th gear if the upshift paddle shifter is pulled when driving in 5th gear, and the shift indicator displays "5" in 2 seconds, then goes off. The transmission stays in 1st gear if the downshift paddle shifter is pulled when driving in 1st gear, and the shift indicator displays "1" in 2 seconds, then goes off.

The transmission stays in the current gear and does not upshift to the next higher gear if the upshift paddle shifter is pulled while driving below the minimum allowable speed for, and the shift indicator blinks the number of the next higher gear several times, then returns to the number of the current gear.

Likewise, the transmission does not downshift to the next lower gear if the downshift paddle shifter is pulled while driving over the maximum allowable speed, the transmission stays in the current gear, and shift indicator blinks the number of the next lower gear several times, then return to the current gear number.

D-paddle shift mode is canceled by the mode control system when the PCM determines the driver is driving under normal conditions and when the vehicle comes to a complete stop.





S Automatic Shift Mode and Sequential Shift Mode

S has two shifting modes; the automatic shift mode and the sequential shift mode. In S automatic shift mode, the transmission upshifts and downshifts automatically from 1st through 4th gear, and the paddle shifters are ready to be activated to switch to the sequential shift mode. In the automatic shift mode, the shift indicator and the M indicator in the gauge control module do not come on.

When the upshift paddle shifter (+; upshift switch) or downshift paddle shifter (-; downshift switch) is pulled, the automatic shift mode is canceled, and the sequential shift mode comes into operation. The shift indicator displays the number of the selected gear, and the M indicator comes on. In the sequential shift mode, the driver can shift up and down manually from 1st through 5th gear by using the paddle shifters, much like a manual transmission. The paddle shifters are installed on the back of the steering wheel, and the driver can shift gears by pulling the paddle shifters without taking either hand off the steering wheel.

In the sequential shift mode, the transmission must be shifted up and down by pulling the paddle shifters. However, the transmission cannot downshift and stays in the current gear if the downshift paddle shifter is pulled while the vehicle is coasting at a speed that would cause the engine to over-rev by downshifting the transmission, and the shift indicator blinks the number of the selected gear several times, then returns to the number of the current gear. If the vehicle speed reaches an appropriate speed while the shift indicator is blinking the number of the selected gear, the transmission downshifts and the shift indicator displays the selected gear. The transmission also cannot upshift and stays in the current gear if the upshift paddle shifter is pulled while driving below an appropriate upshifting speed, the shift indicator blinks the number of the selected gear several times, then returns to the number of the current gear. If the vehicle speed reaches the an appropriate upshift speed while the shift indicator is blinking the number of the selected gear, the transmission upshifts and the shift indicator displays the selected gear.

This mode has automatic downshifting areas so the vehicle can run smoothly with more power to cope with upcoming acceleration. When coasting in 5th gear or 4th gear, the transmission downshifts to the next lower gear if the vehicle slows down to the programmed speed, or by pressing the brake pedal.

When the transmission decelerates to a stop, the transmission shifts to 1st gear automatically. The transmission can be shifted to 2nd gear by pulling the upshift paddle shifter while the vehicle is stopped, and the vehicle can start off in 2nd gear.

The sequential shift mode is canceled when moving the shift lever to any position other than S.





Clutch Pressure Control

The PCM actuates A/T clutch pressure control solenoid valves A, B, and C to control the clutch pressure. When shifting between gears, the clutch pressure regulated by A/T clutch pressure control solenoid valves A, B, and C engages and disengages the clutch smoothly.

The PCM receives input signals from the various sensors and switches, processes the data, and outputs current to A/T clutch pressure control solenoid valves A, B, and C.





Lock-up Control

Shift solenoid valve D controls the hydraulic pressure to switch the lock-up shift valve and lock-up ON and OFF. The PCM turns shift solenoid valve D and A/T clutch pressure control solenoid valve A ON, and lock-up starts. A/T clutch pressure control solenoid valve A regulates and applies hydraulic pressure to the lock-up control valve to control the amount of lock-up.

The lock-up mechanism operates in all five gears.

PCM A/T Control System Electrical Connections - Seven-position Transmission:

PCM A/T Control System Electrical Connections - Five-position Transmission:

PCM A/T Control System Input and Output (Part 1):

PCM A/T Control System Input and Output (Part 2):

PCM A/T Control System Input and Output (Part 3):

PCM A/T Control System Input and Output (Part 4):