Control System (Ecu); Control System - TOHATSU MFS 25D Service Manual

3) Control System (ECU)

If the ECU (Engine Control Unit) fails, the engine stops.
The ECU provides the following functions.
1. Calculates the most suitable fuel injection amount and ignition timing based on the engine revolution speed,
throttle position, intake vacuum, intake air temperature and engine temperature.
2. Controls the fuel injectors, ignition coils and ISC (Idle Speed Control) valve.
3. Controls the warning lamp (LED).
4. Controls the engine low speed ESG function.
5. Controls the engine high speed ESG function.
6. Memorizes engine operation information.
Monitoring and failure diagnosis can be carried out using a PC on which TOHATSU DIAGNOSTICS (software) is
installed and diagnostics harness.

(2) Control System

The ECU (Electronic Control Unit) is installed in the cylinder block via a bracket. Data received from sensors such as
pulser coil, T-MAP (Manifold Pressure, Manifold Temperature) sensor and engine temperature sensor are processed
in a computer to drive the actuators (fuel injectors, ISC valves, etc.) and control the fuel injection amount and ignition
timing according to the operating conditions then.
The principal control items are as follows.
Control Item
Ignition Timing
Fuel Injection Amount
ISC
(Idle Speed Control)
Fuel Feed Pump
Tachometer
Warning Buzzer*1
Warning Lamp (LED)
(The tachometer warning
lamp synchronizes
and lights or flashes
accordingly.)
Memorizing operational
data
*1: Only for Remote Control Models
4st 25/30 2022
Sets the most suitable ignition timing according to the current operating conditions.
Sets the most suitable fuel injection amount according to the current operating conditions.
Stabilizes the engine revolution speed during idling or low speed running by actuating
the ISC valve to control the air flow in the bypass passage.
Controls the actuation of the fuel feed pump (FFP).
Outputs the tachometer actuation pulses.
Per Crankshaft Rotation (6 Pulses) (12 Poles)
Emits a warning sound when an error is detected.
• Only for 0.5 seconds after starting: Indicates that system operation is normal and there
is no problem.
• Continuous sound: When engine high speed ESG is "ON"
When the engine temperature is abnormally high (85°C or higher)
When engine oil pressure is abnormally low
• Intermittent sound: When water temperature sensor or T-Map (Manifold Pressure)
sensor is defective or sensor circuit is disconnected.
The lamp lights or flashes when an error is detected.
• Lit only for 5 seconds after starting: Indicates that system operation is normal and there
is no problem.
• Lit : When engine high speed ESG is "ON"
When the engine temperature is abnormally high (95°C or higher)
When engine oil pressure is abnormally low
• Flashing: Failure of the engine temperature sensor or T-MAP (manifold pressure, intake
air temperature) sensor is defective or circuit disconnection
Manages the following engine operation information:
• Engine operating hours
• Maximum water temperature record (Maximum water temperature and time of occurrence)
• Engine high speed ESG operation record
• Engine low speed ESG operation record
• Malfunction records
Control Description
4
4-21