Efi Control System - 2.0l Nissan 200SX S12

DESCRIPTION

The EFI Electronic Control System is a computerized fuel control system. A single control unit monitors a variety of sensors, including the following

1. Airflow Meter
2. Air Regulator
3. Exhaust Gas Sensor
4. Fuel Injector
5. IC Ignition Unit
6. Ignition Switch
7. Neutral Switch
8. Spark Switching
9. Throttle Valve Switch
10. Water Temperature Sensor
11. Heater Fan Switch, Light Switch, Power Steering Oil Pressure Switch
12. Barometric Pressure Sensor (Except Calif.)

EFI CONTROL UNIT

The EFI control unit calculates basic injection pulse width by processing signals from ignition and airflow meter. Receiving signals from each sensor, the unit adds various enrichments, which are programmed into the control unit, to the basic injection amount. Thus the optimum amount of fuel is injected.

The control unit is located on driver's side kick panel. It is not serviceable and should not be opened. A monitor lamp is provided on lower side of unit so system operation can be checked. The control unit contains memory and logic circuits that enable it to interpret sensor inputs and control different engine systems.

Airflow Meter

Airflow meter measures the quantity of intake air, and sends a signal to the control unit. The airflow meter is provided with a flap in the air passage. During idling operation when the amount of intake air is small, the air flows parallel with the flap through the by-pass port so that the specified intake airflow can be provided correctly.

An air temperature sensor is installed in the passage. The by-pass port has the air by-pass screw which regulates idle mixture ratio. The air by-pass screw is set and sealed at the factory.

Temperature Sensor

Coolant temperature sensor is located in the coolant outlet. On all models, sensor provides a varying resistance measurement as coolant temperature changes.

Exhaust Gas Oxygen Sensor

This component measures the amount of unburned oxygen in the exhaust and provides a voltage signal which is used to adjust fuel mixture (amount of injection time).

Throttle Valve Switch

The throttle valve switch is open when the throttle is being moved and closed when the engine is idling. The switch also contains a set of full throttle contacts.

Air Regulator

The air regulator by-passes the throttle valve to control the quantity of air available for engine idling speed during warm-up. A bi-metalic thermocouple, heater and rotary shutter are built into the air regulator. When the temperature is low, the air by-pass port is open. As the engine starts and electric current flows through a heater, the thermocouple begins to rotate the shutter to close off the by-pass port. The air passage remains closed until the engine is stopped and the temperature drops.

Spark Plug Switching Control

The spark plug switching control system is designed to change the ignition system from 2-plug to 1-plug ignition during heavy load driving in order to reduce engine noise. The system also functions to advance ignition timing by a specified value during 1-plug ignition.

Idle-up Control

The idle speed is compensated by the EFI control unit to prevent rough idle when battery voltage is below 12 volts, when load signal is on and engine RPM is less than 1500 RPM, when engine speed is less than 460 RPM, when atmospheric pressure is less than 26.38 in. Hg, or when airflow meter is malfunctioning. The control unit senses the conditions, and determines an On/Off signal. The signal from the control unit is transmitted to the idle-up solenoid valve to stabilize idle speed.

Fuel Pump

The EFI control unit operates electric fuel pump. When ignition switch is turned to "ON" or "START" position, the fuel pump operates. It will operate for 16.7 seconds before engine is cranked before shutting off.

Fuel Injection

The control unit determines how long voltage is provided to each injector. The injection time will determine how much fuel is injected. For more information, see FUEL INJECTION SYSTEM - BOSCH AFC article in FAULT ISOLATION in ENGINE PERFORMANCE.

Automatic Transmission Lock-up Control

The EFI control unit controls transmission lock-up according to engine conditions. Control unit prevents lock-up when idle switch is on and/or coolant temperature is below 131°F (50°C).

INTRODUCTION

The self-diagnostic system diagnoses malfunctions in major sensors and actuators of the system. The ECU constantly monitors the function of these sensors and actuators, regardless of ignition key position. If a malfunction occurs, the information is stored in the ECU and can be retrieved from the memory by turning on the diagnostic mode selector, located on the side of the ECU. The ECU is located on driver's side kick panel. The selector is an "ON" and "OFF" switch, that is operated by inserting a screw driver through the appropriate hole on the side of the ECU.

A malfunction in the system is interpreted by the number of blinks of both the Red and Green light emitting diodes (LEDs) on the control unit. Red should blink first, followed by Green. Red represents the tens digit and Green represents unit digits. For example, if Red blinks 2 times followed by Green blinking 5 times, this would represent code 25.

SELF-DIAGNOSTIC PROCEDURES

1. Verify that diagnosis mode selector is turned to "OFF" position. Turn ignition switch to "ON" position. Make sure inspection lamps on control unit stay on. If okay, proceed to next step. If no good, check harness for battery source. If okay, replace control unit.
2. Turn diagnosis mode selector to "ON" position. Inspection lamps on control unit should display codes 23, 24 (M/T model), 31 and 32. If not, write down codes displayed.
3. Depress accelerator pedal and release. Inspection lamps on control unit should display codes 24, 31 and 32. If not, write down codes displayed.
4. Shift transmission control lever to the neutral gear position, then to top gear position, and then to neutral. Inspection lamps on control unit should display codes 31 and 32. If not, write down codes displayed.
5. Start engine. Inspection lamps on control unit should display code 31. If not, write down codes displayed.
6. Turn air conditioner switch to the "ON" position, and then turn the switch to the "OFF" position. Inspection lamps on control unit should display code 44. If not, write down codes displayed.
7. Turn diagnosis mode selector to the "OFF" position. Turn engine off. Check malfunctioning area as listed in component testing. Erase memory of self-diagnosis results.

EFI Electronic Control System Components for 200SX. Scheme 20

MEMORY ERASURE

Turn self-diagnosis mode selector to "OFF" position. Disconnect the control unit harness connector or battery cable. Keep it off for more than 15 seconds. Reconnect harness connector or battery cable.

Scheme 21

Scheme 22

Scheme 23

1. Visually check the air cleaner, hoses and ducts, EGR valve operation, electrical connectors, gaskets and throttle valve and switch. Start engine and warm up until water temperature indicator points to the middle of the gauge.
2. Run engine at no-load at 2000 RPM for about 2 minutes. Perform EFI self-diagnosis. Repair or replace components as necessary. If engine does not run smoothly, clean and inspect injectors and replace if necessary.
3. If engine runs smoothly, disconnect distributor vacuum hose from distributor and plug hose. Run engine at 2000 RPM for about 2 minutes under no-load. Run engine at idle speed and make sure the engine speed is below 1000 RPM. Race engine 2 or 3 times under no-load and run engine for about one minute at idle speed.
4. Check ignition timing. Timing should be within 2° of TDC on A/T models, and within 6° on M/T models. If not okay, adjust and return to step 3. If okay, connect distributor vacuum hose.
5. Run engine under no-load at about 2000 RPM for about 2 minutes. Make sure that even if Red lamp goes on, Green lamp on control unit goes on and off more than 9 times during 10 seconds at 2000 RPM. If not, go to step 8. If okay, go to next step.
6. Race engine 2 or 3 times under no-load and then run engine at idle speed. Check inspection lamp for Red and Green blinking simultaneously. If they don't, go to step 13. If they do, again race engine 2 or 3 times under no-load and then run engine at idle speed.
7. Check idle speeds against those listed in idle speeds table. If okay, test is complete. If no good, adjust.
8. If lights did not flash as listed in step 5, turn off engine and disconnect battery ground cable. Disconnect 20-pin connector from control unit. Disconnect exhaust gas sensor harness connector and connect terminal for exhaust gas sensor to ground with a jumper wire. Check for continuity between terminal 4 of 20-pin connector and ground metal of vehicle body. (Scheme 23) IDLE SPEEDS Application RPM M/T 650-850 A/T In "Drive" position 600-800 (Scheme 21): Schematic & Vacuum Diagram EFI Control System
9. If continuity does not exist, repair or replace harness and return to step 1. If continuity exists, connect 20-pin connector and battery ground. Disconnect jumper wire. Disconnect engine coolant temperature sensor harness connector. Connect a 2500-ohm resistor between harness connector terminals.
10. Start engine and warm up until water temperature indicator points to the middle of the gauge. Race the engine 2 or 3 times under no-load, and run at idle speed.
11. Check idle CO. It should be below 8%. After checking, disconnect the resistor from terminals of temperature sensor and reconnect connector to sensor. If CO was not okay, go to step 13. If okay, go to next step.
12. Replace exhaust gas sensor and make sure that even if Red lamp goes on, that Green inspection lamp goes on and off more than 9 times in 10 seconds when engine is run at 2000 RPM. If no good, replace control unit.
13. If CO was not correct in step 11, disconnect jumper wire from exhaust gas sensor harness. Connect exhaust gas sensor harness to sensor. Turn engine "OFF" and remove airflow meter from vehicle. Drill a hole in plug which seals variable resistor of airflow meter and remove seal plug. Install airflow meter on vehicle. Start engine and warm up until indicator is at middle of gauge. (Scheme 22): EFI Control Unit (Scheme 23): EFI Control Unit 20-Pin Connector Terminal Locations
14. Adjust idle mixture ratio by turning air by-pass screw of airflow meter so that inspection lamps blink simultaneously. If found to be not adjustable, replace airflow meter and return to step 1. If adjustable, go to next step.
15. Turn engine off, and remove airflow meter. Install a new seal plug into variable resistor hole. Install airflow meter to vehicle and return to step 1.

Scheme 24

1. Disconnect the 20-pin connector and measure the resistance between terminals No. 6 and 11, 6 and 15, and 6 and 16. (Scheme 23) If no good, go to next step. If okay, check airflow meter flap. If flap is okay, replace control unit. If not okay, replace airflow meter.
2. If resistance readings in step 1 were not correct, check airflow meter resistance readings between terminals E and B, E and C, and E and D on airflow meter. Resistance should be as listed in table. If no good, replace the airflow meter. (Scheme 24): Airflow Meter Connector Terminals
3. If okay, check resistance readings between terminals B, C, D, E and ground. Resistance should be infinity. If okay, check airflow meter flap. If no good, replace airflow meter.

AIRFLOW METER RESISTANCE VALUES

WATER TEMPERATURE SENSOR (CODE 13)

1. Disconnect 20-pin connector and measure the resistance between terminals No. 3 and 5 (ground). (Scheme 23) When water temperature is above 68°F (20°C), resistance should be below 2700 ohms. When temperature is below 68°F (20°C), resistance should be above 2300 ohms. If resistance readings are okay, check harness. If harness is okay, replace control unit.
2. If resistance readings were no good in step 1, remove sensor from vehicle. Subject sensor to immersion by placing it in water at various temperature. Check sensor resistance readings. At 32°F (0°C), resistance should be 5000 ohms. At 86°F (30°C), resistance should be about 2400 ohms, and at 140°F (60°C), resistance should be about 650 ohms.
3. If resistance readings are no good, replace water temperature sensor. If no good, check harness. If harness is okay, replace control unit.

IGNITION SYSTEM (CODE 21)

1. Disconnect high tension cable from one spark plug and check hot spark during cranking. If okay, test is complete. If no good, perform EFI self-diagnosis.
2. If self-diagnosis is okay, check distributor, ignition coil and high tension cable and repair or replace if necessary. If okay, replace IC ignition unit.
3. If self-diagnosis was no good, check harness and repair if necessary. If okay, replace IC ignition unit and return to step 1 .

FUEL PUMP (CODE 22)

1. Turn ignition switch to the "ON" position, and listen to the fuel pump operating sound. The sound must be heard for about 5 seconds. If not okay, go to next step. If sound was heard, perform EFI self-diagnosis. If this is okay, end test. If not, replace the ECU.
2. Disconnect EFI 15-pin connector. (Scheme 27) Check voltage between terminal O and ground when ignition switch is turned to the "ON" position. Battery voltage should be present. If okay, go to next step. If no voltage appeared, check body harness (under assist seat) for power source.
3. Check fuel pump for continuity at body harness connector under assist seat. The body harness connector contains 12 pins. Holding the connector so that there are 2 terminals on the left, separated from the rest by a groove, check for continuity between the second and the fourth lower terminals to the right of the groove. If no continuity exists, replace fuel pump. If continuity exists, replace ECU.

Scheme 25

1. Disconnect the 20-pin connector and measure the resistance between terminals 8 and 12. (Scheme 23) With switch released, there should be no resistance. With switch depressed, resistance should be infinity.
2. If no good, measure resistance between terminal F and G on switch connector. (Scheme 25) Resistance should be zero. If okay, go to step 3. If no good, adjust idle switch so that it turns on at idle speed A 250 RPM. If still no good, replace throttle valve switch. (Scheme 25): Throttle Valve Switch Connector Terminals
3. Measure the resistance between terminal F and G on switch connector and body ground. Resistance should be infinity. If okay, check and repair harness if necessary. If harness is okay, replace control unit. If resistance is not okay, replace the throttle valve switch.

TRANSMISSION SWITCH (CODE 24)

1. Disconnect 20-pin connector and measure resistance between terminals 14 and 5. (Scheme 23) Resistance should be as listed. If okay, perform EFI self-diagnosis. If diagnosis not okay, replace ECU. If okay, end test. TRANSMISSION SWITCH RESISTANCES (OHMS) Application Ohms Neutral 0 Except Neutral Infinity
2. If resistance readings test incorrect, check neutral switch for operation. Connect ohmmeter leads across terminals of switch. Continuity should exist when switch button is pressed. If continuity is okay, check EFI and engine harness for continuity. Continuity should exist. If not, repair/replace harness. Perform EFI self-diagnosis. If diagnosis okay, end test. If not, replace ECU.

A/C SWITCH, LIGHTING SWITCH, FAN SWITCH, POWER STEERING SWITCH (CODE 31)

Disconnect 20-pin connector and measure voltage between terminal 7 and body ground. (Scheme 23) With A/C switch turned to the "ON" position, there should be 12 volts. With switch turned to the "OFF" position, there should be no voltage. If not, inspect harness and repair if necessary. If harness is okay, check switches and replace if necessary. If okay, replace control unit.

STARTER SWITCH (CODE 32)

1. Disconnect 20-pin connector and measure the voltage between 9 and 5 (body ground). (Scheme 23) Turn ignition switch to "START" position. If battery voltage is present, perform EFI self-diagnosis. If still not okay, replace control unit.
2. If there is no battery voltage, check harness and repair if necessary. If okay, check starting circuit and replace or repair if necessary. If okay, replace or charge battery.

AIR TEMPERATURE SENSOR (CODE 41)

1. Disconnect 20-pin connector and measure the resistance between terminals No. 2 and 6. (Scheme 23) When cylinder head temperature is above 68°F (20°C), resistance should be below 2700 ohms. If temperature is below 68°F (20°C), reading should be above 2300 ohms.
2. If okay, perform EFI self-diagnosis. If code 41 remains, replace ECU. If no good, check air temperature sensor for insulation between terminals A, E and ground. (Scheme 26) If not, replace air temperature sensor. If okay, measure resistance between terminals A and E.
3. With air temperature above 68° F (20° C), resistance should be below 2700 ohms. With air temperature below 68° F (20° C), resistance should be above 2300 ohms. If okay, check harness and repair or replace if necessary. If okay, perform EFI self-diagnosis. If okay, end test. If not okay, replace ECU.

1. Disconnect 15-pin connector and check voltage between terminal C and ground when ignition is on. (Scheme 27) If battery voltage is present, replace ECU. If not, check air regulator for continuity. Resistance should be 70 ohms across terminals of regulator. If not, replace regulator. If okay, check EFI harness and repair if necessary.

Air Temperature Sensor Locations. Scheme 26

EFI 15-Pin Connector. Scheme 27

INJECTOR

Disconnect 15-pin connector and check voltage between terminals E, A, B, J and ground. (Scheme 27) There should be battery voltage. If okay, test is complete. If not, check each injector for continuity at connector. If there is continuity, check harness. If not, replace injector.

BATTERY SOURCE & GROUND

1. Disconnect 15-pin and 20-pin connectors. Check continuity between terminals 5, K and ground. (Scheme 23)and (Scheme 27). Check voltage between terminal D and ground. There should be battery voltage.
2. If okay, test is complete. If not, repair harness. If harness is okay, test is complete. If no good, check EFI relay. (Scheme 28) Relay should show continuity as listed in table. If not, replace relay.

EFI Relay Terminal Connectors. Scheme 28

EFI RELAY CONTINUITY

Scheme 29

1. Disconnect 15-pin connector and check voltage between terminal I and ground when ignition is on. (Scheme 27) If not okay, go to next step. If there is battery voltage, disconnect 20-pin connector. Turn ignition switch to the "ON" position, and measure the voltage between terminal No. 7 and ground. With the air conditioner switch on, there should be 12 volts present. With air conditioner switch off, there should be no voltage. If okay, go to next step. If no good, check diodes for open circuit. Check switches for battery source. Repair or replace as needed. (Scheme 29): Checking Idle-Up Solenoid Valve
2. Check idle-up solenoid for continuity. (Scheme 29) Resistance should be 30 ohms across the leads of the idle-up solenoid connector. If okay, check EFI harness for continuity and main harness for battery source. Check EFI relay. (Scheme 29) If not good, repair or replace as necessary.

200SX EFI Control System Wiring Diagram (1 Of 2). Scheme 30

200SX EFI Control System Wiring Diagram (2 Of 2). Scheme 31

See also:
• FUEL INJECTION SYSTEM - BOSCH AFC