Operation
Battery voltage is applied on the data link connector power terminal No. 16 (Green/Red wire). The ground terminals, No. 4 & 5 (Black wires) are grounded to the vehicle body.
A diagnostic output is made from the ECM terminal No. 62 to the diagnostic output terminal No. 7 of the data link connector.
Malfunction indicator light (SERVICE ENGINE SOON) power is supplied from the ignition switch. ECM controls the ground of the malfunction indicator light by turning the power transistor in the ECM, ON and OFF.
The malfunction indicator light (SERVICE ENGINE SOON) power is supplied from the ignition switch. The ECM controls the ground of the malfunction indicator light (SERVICE ENGINE SOON) by turning the power transistor in the ECM ON and OFF.
Circuit Operation
The ignition coil is energized by battery positive voltage from ignition switch.
When ECM turn off its internal power transistor, battery positive voltage is applied to ignition power transistor through terminal No. 3 inside ignition coil, causing ignition power transistor to be turned on.
If ignition power transistor is turned on, the primary circuit of the ignition coil is energized by grounding the ignition coil through terminal No. 2 causing the primary current to flow to ignition coil. (Scheme 208)
The ECM controls generator output current by duty-controlling continuity between the generator "G" terminal and ground. For generator output circuit diagram and related connector identification (Scheme 201)
Scheme 201
The ECM increases the engine idle speed by driving the IAC motor when the automatic compressor-ECU sends a A/C on signal to the module. (Scheme 202)
The A/C-ECU detects how the air conditioning is applying load to the engine, and converts the information to a voltage signal (high voltage = low load, low voltage = high load). This voltage receives this A/C switch 2 signal form the automatic compressor controller through terminal No. 24 and determines the idle-up speed according to the high or low air condition load.
Scheme 202
The ECM sends a duty signal to the fan control module according to engine coolant temperature, vehicle speed, and the condition of the A/C switch. (The closer the average voltage at the terminal comes to five volts, the higher the fan speed becomes). For radiator fan control related circuit diagram and connector identification (Scheme 203)
Scheme 203
Battery voltage is applied to the ECM (terminal No. 34) from the condenser fan control relay (LO). The battery voltage is applied on the ECM (terminal 32) from the condenser fan control relay (HI). When the ECM switches on those power transistors, the condenser fan control relay coil is energized, causing current to flow in the circuit. For A/C condenser fan related circuits, components and connectors (Scheme 204)
Scheme 204
Battery voltage is applied to the MFI relay (terminal No. 1 and No. 2). When the ignition switch is turned to the ON position, the battery positive voltage is applied to the ECM (terminal No. 82). When the battery positive voltage is applied, the ECM turns the power transistor in the ECM on and grounds the MFI relay coil. With this, the MFI relay turns on and the battery voltage is supplied to the ECM (terminals No. 12 and No. 25) from the MFI relay (terminal No. 4). Battery voltage is constantly supplied to the ECM (terminal No. 80) as the back up power. The ECM (terminals No. 13 and No. 26) is grounded to the vehicle body. (Scheme 205)
Scheme 205
Battery voltage is applied to fuel pump relay 1 terminal No. 3 from the ignition switch-IG. Ground is provided through terminal No. 2 to chassis ground.
When ignition switch is turned to ON position, battery voltage is applied to the fuel pump relay 2 terminal No. 1 from the fuel pump relay 1 terminal No. 1. Battery voltage is applied to the fuel pump relay 2 terminal No. 3 from ignition switch-IG.
During cranking and while the engine is running, ECM turns on the power transistor in ECM in order to ground the coil of the fuel pump relay 2. Consequently, the fuel pump relay 2 turns supplied the battery voltage to the fuel pump and the fuel pump circuit resistor.
While engine operates with a light load, ECM turns on the power transistor in the ECM in order to ground the coil of the fuel pump relay 3. Consequently, the fuel pump relay 3 turns off, and fuel pump resistor at terminal No. 2 supplies the battery voltage to the fuel pump at terminal No. 5.
While the engine operates with a heavy load, the ECM turns off the power transistor in the ECM, causing the fuel pump relay 3 to turn on. Consequently, the fuel pump relay 3 terminal No. 1 supplies power directly to the fuel pump terminal No. 5. (Scheme 206)
Scheme 206
The battery positive voltage is supplied to the ECM terminal No. 71 (Black/Red wire) via the starter relay during engine cranking. With this, the ECM detects that the engine is being cranked. (Scheme 207)
Scheme 207
The ignition coil is energized by battery positive voltage from ignition switch. When ECM turn off its internal power transistor, battery positive voltage is applied to ignition power transistor (terminal No. 3) inside ignition coil, causing ignition power transistor to be turned on.
If ignition power transistor is turned on, the primary circuit of the ignition coil is energized by grounding the ignition coil through terminal No. 2 causing the primary current to flow to ignition coil. (Scheme 208)
Scheme 208
Description
When A/C is on, battery voltage is applied through the Pink wire to ECM terminal No. 45 from the automatic compressor controller. When battery voltage is applied to the ECM, the ECM turns on the power transistor in the ECM. The ECM delays A/C engagement momentarily while it increases idle RPM. Then the A/C compressor clutch relay coil will be energized. With this, the A/C compressor clutch relay turns on, and the A/C compressor clutch operates. (Scheme 209)
Scheme 209
Battery voltage is applied to charge air cooler water spray switch (MANUAL) output terminal (terminal No. 3) from the ECM (terminal No. 91) via the resistor in the ECM.
Battery positive voltage is applied to the charge air cooler water spray switch (AUTO) output terminal (terminal No. 5) from the ECM (terminal No. 44) via the resistor in the ECM.
Battery positive voltage is applied on the charge air cooler water spray relay (terminal 1 and 3) from ignition switch IG-2.
While the manual switch of the charge air cooler water spray switch turned on or the engine is operating with a high load with auto switch of the charge air cooler water spray switch turned on, the PCM turns on the power transistor in the ECM to ground the charge air cooler water spray relay coil. Consequently, the charge air cooler water spray relay turns on and the charge air cooler water spray relay (terminal No. 2) supplies the battery positive voltage to the charge air cooler water spray motor. (Scheme 210)
Scheme 210
The charge air cooler water spray lamp power is supplied from the ignition switch. The ECM controls the ground of the charge air cooler water spray lamp by turning the power transistor in the ECM on and off. If the auto switch of the charge air cooler water spray switch is on, the ECM illuminates the charge air cooler water spray lamp. (Scheme 211)
Scheme 211
See also:
• SYSTEM & COMPONENT TESTING
• FUEL INJECTORS
• VENTILATION SOLENOID