Ecc Cec System Nissan 300ZX Z31

DESCRIPTION

The Electronic Concentrated Engine Control System (ECCS) is a computerized emission, ignition, and fuel control system. A single control unit monitors a variety of sensors, including the following

1. Mass Airflow Meter
2. Crankshaft Angle Sensor
3. Temperature Sensor
4. Detonation Sensor (Turbo Models)
5. Exhaust Gas Oxygen Sensor
6. Park/Neutral Switch (300ZX Turbo)
7. Throttle Valve Switch
8. Vehicle Speed Sensor (300ZX Turbo)

The computer processes information from these sensors and controls these engine functions

1. Air Injection
2. Air Regulator Control
3. EGR Operation
4. Engine Idle Speed
5. Fuel Injectors
6. Fuel Pump Operation
7. Ignition Timing
8. Mixture Ratio

Maxima ECCS Component Locations. Scheme 18

ECCS CONTROL UNIT OPERATION

The control unit is located under left side of dash on Maxima, and on passenger's kick panel on 300ZX and 300ZX Turbo. The unit is not serviceable and should not be opened. Monitor lamps are 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

Air mass meter measures the mass flowrate of the incoming air. Measurements are made by measuring amount of heat dissipated from the hot wire placed in the stream of intake air.

CRANKSHAFT ANGLE SENSOR

The crankshaft angle sensor, which is built into the distributor, has 2 diodes and a wave-forming circuit. When a signal rotor plate passes the space between light emitting diode (LED) and photo diode, the slit to the signal rotor plate alternately cuts the light which is sent to the photo diode from the LED. This causes a pulsating voltage which is converted into an on-off pulse by the waveforming circuit and sent to the control unit.

TEMPERATURE SENSOR

On Maxima and 300ZX models, a cylinder head temperature sensor is located in the cylinder head near the thermostat housing. Both sensors provide a varying resistance measurement as engine temperature changes.

300ZX & 300ZX Turbo ECCS Component Locations. Scheme 19

DETONATION SENSOR

The detonation sensor is located on passenger's side of engine block. It sends a signal when "knocking" occurs. The control unit modifies ignition timing to reduce detonation.

VEHICLE SPEED SENSOR

The vehicle speed sensor provides a vehicle speed signal to the ECCS control unit. The speed sensor consists of a reed switch, which is installed in the speed meter unit and transforms vehicle speed into a pulse signal. On digital type speedometer models, the sensor consists of an LED, photo diode, shutter and wave forming circuit. Its principle is the same as that of the crank angle sensor.

EXHAUST GAS OXYGEN SENSOR

This component measures the amount of unburned oxygen in the exhaust. It provides a voltage signal which is used to adjust fuel mixture (amount of injection time), so that proper combustion occurs.

FUEL TEMPERATURE SENSOR

The fuel temperature sensor is built into the pressure regulator, and senses fuel temperature. When the fuel temperature is higher than the specified level, the ECCS control unit enriches the fuel mixture.

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. These are used on electronically controlled automatic transmission on Maxima, 300ZX and 300ZX Turbo models.

AIR INJECTION

The Air Injection Valve (AIV) sends secondary air to the exhaust manifold, utilizing a vacuum caused by exhaust pulsation in the exhaust manifold. When exhaust pressure is below atmospheric pressure (negative pressure), secondary air is sent to the exhaust manifold. When exhaust pressure is above atmospheric pressure, reed valves prevent secondary air from being sent back to the air cleaner.

EGR OPERATION

Exhaust gas recirculation is controlled by the ECCS. A signal is sent to the vacuum control modulator, providing a regulated vacuum supply to open the EGR valve. EGR operation is affected by cylinder head temperature, throttle valve position and ignition switch position. Recirculation takes place when the engine is operated above idle with cylinder head temperatures between 135-239° F (57-115° C).

ENGINE IDLE SPEED

Idle speed is controlled by the ECCS control unit, corresponding to engine operating conditions. The ECCS control unit senses engine conditions and determines the best idle speed at each cylinder head temperature and gear position. The control unit then sends an electronic signal corresponding to the difference between the best idle speed and the actual idle speed to the AAC valve.

FUEL INJECTION

The fuel injector is a small solenoid valve, to which high pressure fuel is supplied. The ECU controls the solenoid coil within the injector. The coil, when energized, opens a ball valve which allows fuel to pass through a swirl orifice and into the manifold.

FUEL PUMP

The ECCS control unit operates the electric fuel pump. When ignition switch is turned to the "ON" or "START" position, the fuel pump operates. If ignition is on and no signal is received from crank sensor for more than one second, the fuel pump stops. It will operate for 5 seconds before engine is cranked, and will then stop if engine is not cranked over at 20 RPM or more.

IGNITION TIMING

The ECCS control unit uses sensor input to determine correct timing. It sends a signal to a power transistor located in the coil, which permits current to flow through coil. Timing is advanced and retarded by the control unit based on sensor input, built-in programming and detonation sensor signals.

Maxima ECCS Schematic & Vacuum Diagram Note direction of flow. Scheme 20

TESTING & DIAGNOSIS

Operation

The injector cooling fan operates to cool down the temperature of fuel inside the injector and the fuel gallery when engine is stopped under high temperature condition.

Injector Cooling Fan Schematic. Scheme 21

Injector Cooling Fan Flow Chart. Scheme 22

Injector Cooling Fan Operational Chart. Scheme 23

Fan Motor

1. Make sure that continuity exists between terminals of fan motor.
2. Apply battery voltage to the terminals of fan motor. If fan motor does not operate, replace.

FAN MOTOR TIMER UNIT

Check the timer unit with a battery source and a bulb (12V-3W), following the procedure below.

Fan Motor Timer Unit Check. Scheme 24

1. Connect terminal 6 to negative terminal of power source, terminal 5 to test lamp terminal and the other test lamp terminal to negative terminal of the power source.
2. Connect terminal 1 to positive terminal of power source. If test lamp does not glow then it is OK. If test lamp glows then go to step 3.
3. Connect terminal 2 to positive terminal of power source and disconnect it. (Operate timer)
4. Connect terminal 9 to negative terminal of power source. If test lamp glows then it is OK. If test lamp does not glow then go to step 5.
5. Make sure that test lamp should remain on for about 17 minutes after step 3 is performed, and then go out.
6. While test lamp is on, connect terminal 2 to positive terminal of power source. If test lamp goes out then it is OK. If it doesn't go out then it is not OK.

WATER TEMPERATURE SWITCH

1. Remove water temperature switch
2. Check water temperature switch for proper operation.

Operating Temperature

OFF - ON @ 212°F (100° C).

SELF-DIAGNOSTIC SYSTEM OPERATION

The self-diagnostic system is useful to diagnose malfunctions in major sensors and actuators of the ECCS 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 selector is also an on and off switch, yet it is operated by inserting a screw driver through the appropriate hole on the side of the ECU. (Scheme 25)

A malfunction in the system is interpreted by the number of blinks of both the Red and Green light emitting diodes (LEDs) on the BECCS control unit. (Scheme 25) 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 No. 25.

ECCS Control Units. Scheme 25

SELF-DIAGNOSTIC SYSTEM PROCEDURES

1. Verify that diagnosis mode selector is turned fully counterclockwise. Turn ignition switch to the "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 harness is okay, replace control unit.
2. Turn diagnosis mode selector fully clockwise. Depress accelerator pedal, then release. On 300ZX Turbo only, shift transmission control lever from Neutral to other speeds, and then back to Neutral.
3. On all models, start engine. Apply brakes and shift to "D" (A/T models). On 300ZX Turbo, drive vehicle at more than 6 MPH.
4. Turn one of the load switches on and off for all models except 300ZX Turbo. Code 31 will be erased after the E.C.C.S. control unit detects one of the following load signals: Power steering oil pressure switch, A/C heater switch, Headlamp switch, Rear defogger switch, Radiator fan switch. On 300ZX Turbo, turn air conditioner switch and heater fan switch on and off.
5. Make sure that inspection lamps on control unit are displaying code No. 44. If not, write down any alternate code being flashed. If okay, turn diagnosis mode selector fully counterclockwise. Turn engine off. Check malfunctioning area as listed in component testing. Erase memory of self-diagnosis results. See MEMORY ERASURE below.

MEMORY ERASURE

Turn ignition switch to the "ON" position. Turn diagnosis mode selector on (fully clockwise), and keep it there for more than 2 seconds. Turn diagnosis mode selector off (fully counterclockwise), and keep it there for more than 2 seconds. Turn ignition switch off.

Scheme 26

Scheme 27

1. Make sure idle speed, engine operating temperature and ignition timing are normal. Make sure diagnosis mode lever is turned fully counterclockwise.
2. Run engine at about 2000 RPM for 2 minutes under no-load. Make sure that Green inspection lamp on control unit goes on and off more than 5 times in 10 seconds while engine is running at 2000 RPM.
3. If not, go to step 7). If okay, disconnect throttle valve switch harness connector. Race engine under no-load 2 or 3 times and run at idle speed. Inspection lamps should blink. If so, connect throttle valve switch connector. Test is complete. If not, go to next step. (Scheme 26): 300ZX ECCS Schematic & Vacuum Diagram Note direction of flow.
4. Turn off engine 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.
5. Adjust idle mixture ratio by turning variable resistor 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.
6. Turn off engine and remove airflow meter. Install a new seal plug into variable resistor hole. Install airflow meter to vehicle. Connect throttle valve switch harness connector and return to step 1).
7. If inspection lamps failed to flash as specified in step 2), check exhaust gas sensor harness. Turn off engine and disconnect battery ground cable. Disconnect 16-pin connector from control unit.
8. Disconnect exhaust gas sensor harness connector and connect terminal for exhaust gas sensor to ground with a jumper wire. Check for continuity between terminal No. 24 of 16 pin connector and ground metal of vehicle body. (Scheme 27) (Scheme 27): 300ZX Turbo ECCS Schematic & Vacuum Diagram Note direction of flow.
9. If continuity does not exist, repair or replace harness and return to step 1). If continuity exists, disconnect cylinder head temperature 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 0.2-4.0%. After checking, disconnect the resistor from terminals of temperature sensor and reconnect connector to sensor. If CO was not okay, go to step 4). If okay, go to next step.
12. Replace exhaust gas sensor and make sure inspection lamp goes on and off more than 5 times in 10 seconds when engine is running at 2000 RPM. If okay, return to step 1). If not, replace the ECCS control unit and return to step 1).

CRANK ANGLE SWITCH TEST - CODE 11

1. Turn ignition switch to the "ON" position. Check voltage between crank angle sensor connector terminal B and ground. Battery voltage should be present. Turn ignition switch to the "OFF" position, and check resistance between terminal D and ground. Resistance should be zero ohms. If not, check harness between crank angle sensor and control unit, and harness to the battery. If okay, go to next step.
2. With ignition switch in the "OFF" position, disconnect ECU 20-pin connector and measure the resistance between terminals No. 17 and 8. Resistance should be infinite. Connect crank angle sensor harness terminals with a jumper wire, and measure the resistance between terminals No. 17 and 8. No resistance should be present. If no good, repair or replace harness. If okay, check crank angle sensor for any damage. Visually inspect the unit. If damaged, replace. Perform self-diagnosis. If code No. 11 still flashes, replace ECU.

20-Pin Connector Terminals. Scheme 28

16-Pin Connector Terminals. Scheme 29

Scheme 30

1. Disconnect 16-pin connector and connect terminal No. 26 to ground with a jumper wire. Turn ignition to the "ON" position and measure voltage between terminals No. 31 and 26. Voltage should be 0.6-1.0 volts. (Scheme 29)
2. If voltage is good, go to next step. If voltage is no good, check harness for continuity. If okay, go to next step. If no good, turn ignition switch to the "ON" position and measure voltage between terminals No. 26 and 27. Battery voltage should be detected. If okay, go to next step. If not, repair harness.
3. Disconnect airflow meter connector. (Scheme 30) Apply battery voltage to terminals D and E. Measure voltage between B and D. Voltage should be 1.1-2.1 volts. If no good, replace airflow meter. If okay, go to next step. (Scheme 30): Airflow Meter Connectors (Maxima)
4. Remove airflow meter. Apply battery voltage to terminals B and C. Blow air through airflow meter and measure voltage between terminals D and C. Voltage should be 1.8-2.2 volts at 66 lb. (30 kg) per hour of airflow. If not correct, replace airflow meter. If voltage reading was as indicated, replace control unit.
5. Disconnect airflow meter harness connector. Measure the resistance between airflow meter harness connector terminal D and ground. Resistance should be zero ohms. If not, repair or replace. If okay, turn ignition switch to the "ON" position and measure voltage between harness connectors B and D. Battery voltage should be present. If not okay, check EFI relay and harness related battery source. If okay, go to next step.
6. Turn ignition switch to the "OFF" position. Disconnect ECU 16-pin connector and measure the resistance between the following terminals: 26-30, 26-31, 30-31, 36-26, 36-30, 36-31. Resistance should be infinite. Connect airflow meter harness connector terminals C, E and F with a lead wire and measure the resistance between terminals No. 26-30, 26-31, and 30-31. Resistance should be zero ohms. If not, repair or replace harness. If okay, go to next step.
7. Remove airflow meter. Apply battery voltage to terminals D and E. Measure voltage between terminals B and D. (Scheme 30) Voltage should be 1.1-2.1 volts. If no good, replace airflow meter.
8. If okay, blow through airflow meter and measure voltage between terminals B and D. Voltage should be 2-4 volts. If okay, replace control unit. If no good, replace airflow meter.

AIRFLOW METER RESISTANCE VALUES

AIRFLOW METER TEST - CODE 12 (300ZX)

1. Check power source. Turn ignition switch ON. Check voltage between terminal E and ground. Battery voltage should exist and if it does go to step 2. If it does not, check the harness continuity between air flow meter and battery, main relay, "BR" fusible link and power source for ECU.
2. Check ground circuit. Turn ignition switch OFF. Disconnect air flow meter harness connector. Check resistance between C, D and ground. Shield wire. Resistance should be approximately 0 ohms. If ok, go to step 3. If it is not ok, check engine ground and harness connection between air flow meter and ground.
3. Check ECU input signal. Reconnect air flow meter harness connector. Start engine, make sure that voltage between ECU terminal 31 and ground changes by racing engine with accelerator pedal. Output voltage should change to approximately 2-4 volts. If ok, go to step 4. If not ok, check harness continuity between ECU and air flow meter by doing the following: Stop the engine Disconnect air flow meter harness connector Disconnect ECU 16-pin harness connector Check resistance between terminal B and ECU terminal 31. Resistance should be approximately 0 ohms. If ok, replace air flow meter.
4. Reinstall any part removed. Erase self-diagnosis memory. Perform driving test and then perform self-diagnosis (MODE III) again. If ok then testing is complete. If not ok, perform ECU input/output signal inspection test. If not ok, recheck ECU pin terminals damage or the connection of ECU harness connector.

Air Flow Meter Terminals (300ZX). Scheme 31

ECU Connector Terminals (300ZX). Scheme 32

COOLANT TEMPERATURE SENSOR TEST - CODE 13

1. Disconnect 16-pin connector. Measure the resistance between terminals No. 23 and 26. If resistance readings are okay, replace control unit. If not okay, check wiring harness. If harness is okay, place the sensor into water that is maintained at the specified temperature(s) in the «COOLANT SENSOR TEMPERATURE/RESISTANCE RELATIONSHIP»(/nissan/300zx/z31-1983-1989/remont/testing-diagnostics/#ecc-cec-system) table. COOLANT SENSOR TEMPERATURE/RESISTANCE RELATIONSHIP Temperature: °F (°C) Resistance Ohms 14°F (10°C) 7000-11400 68°F (20°C) 2100-2900 122°F (50°C) 680-1000 176°F (80°C) 260-390 212°F (100°C) 180-200
2. If the readings of the sensor do not match the ones in the table, replace temperature sensor. If readings match the ones in the table, sensor is good, replace the control unit.

VEHICLE SPEED SENSOR TEST - CODE 14 (TURBO V6)

1. Disconnect speedometer cable from transmission. Disconnect 16-pin connector from ECCS control unit and check continuity between terminal No. 29 and ground. (Scheme 29) Slowly turn cable.
2. An on-off pulse should be detected. Ignition switch should be in the "ON" position if vehicle has digital speedometer, in the "OFF" position with needle-type speedometer. If no pulse, check harness and vehicle speed sensor. If pulse is good, replace ECCS control unit.

ECCS 20-Pin Connector Terminal Locations. Scheme 33

Scheme 34

Scheme 35

1. On 300ZX models and on Maxima, check spark plugs, ignition wires, distributor cap and distributor rotor. If okay, check battery voltage at power transistor. Disconnect the harness connector at power transistor. Turn ignition switch to the "ON" position and measure the voltage. Measure terminals No. 1 and 4 on Maxima, and No. 1 and 3 on 300ZX models. If battery voltage is not present, replace or repair harness. (Scheme 34): 300ZX & 300 ZX Turbo Power Transistor Terminals (Scheme 35): Maxima Power Transistor Terminals
2. If voltage was present, check harness between ECU and power transistor. Disconnect ECU 20-pin connector and check for insulation between terminals No. 3, 5 and ground. No resistance should exist. Place a lead wire across terminals No. 3 and 2 of harness connector, and measure resistance between terminals No. 3 and 5 in 20 pin connector. If no resistance is found, repair or replace harness. If resistance was found, check power transistor for continuity. Refer to MAXIMA POWER TRANSISTOR CONTINUITY VALUES table. MAXIMA POWER TRANSISTOR CONTINUITY VALUES Tester Terminal (+ / -) Continuity 1/2 Yes 1/3 Yes 1/4 Yes 2/1 No 2/3 No 2/4 Yes 3/1 Yes 3/2 Yes 3/4 Yes 4/1 No 4/2 Yes 4/3 No
3. On 300ZX models, check power transistor continuity. Using an ohmmeter measure current of tester between terminals 1 & 3, 2 & 3 and 2 & 1. Continuity should exist.
4. On Maxima and 300ZX models, if no continuity exists, replace power transistor. If continuity exists, check ignition coil for continuity. Resistance between terminals No. 1 and 2 should be one ohm. Resistance between terminals No. 1 and 3 should be 10,000 ohms. If okay, replace ECU. If not okay, replace ignition coil, and begin test again.

View of Ignition Coil Terminals. Scheme 36

Scheme 37

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.
2. On Maxima and 300ZX if sound was heard, go to step 3). If sound was not heard, check fuel pump relay and fuse. Check for continuity between terminals No. 1 and 2 of relay connector, and for insulation between terminals 3 and 4. (Scheme 37) If not good, replace fuel pump relay. If okay, check harness between ECU and fuel pump, and harness between fuel pump and fuse block. If harness is defective, replace/repair. If harness is okay, go to step 4). (Scheme 37): Fuel Pump Relay Connector Terminals On Maxima and 300ZX
3. Disconnect ECCS 15-pin connector, and check voltage between terminal No. 108 and ground when ignition switch is turned to "ON". (Scheme 38) Battery voltage should be present. If not, check harness, and replace or repair as necessary.
4. Check fuel pump for continuity between leads of fuel pump connector. On Maxima and 300ZX, also check pump connector terminals for insulation. If not okay, replace fuel pump. If okay, replace ECU on Maxima and 300ZX.
5. Turn ignition switch to "ON". Check voltage between fuel pump harness connector terminal D and ground. Battery voltage should exist for 5 seconds after turning ignition switch to "ON". If okay, go to next step. If not okay, check harness continuity between fuel pump and ground, fuel pump relay, and power source to the ECU.
6. Check ground circuit. Turn ignition switch to "OFF". Disconnect fuel pump harness connector. Check resistance between terminal E and ground. No resistance should exist. Disconnect fuel pump harness connector, and check resistance between terminals D and E. No resistance should be present. If not okay, replace fuel pump. If okay, check crank angle sensor circuit, and test again if it is necessary.

ECCS 15-Pin Connector Terminal Locations. Scheme 38

Scheme 39

1. Check throttle valve switch for continuity between terminals 18 and 25. (Scheme 39) If there is continuity, go to next step. If there is no continuity, adjust switch so that switch turns on at idle A 250 RPM. If not adjustable, replace throttle valve switch. If adjusted, go to next step. (Scheme 39): Throttle Valve Switch Connector
2. Check for insulation between terminals 18, 25, and ground. If no insulation, replace throttle valve switch. If there is insulation, perform ECCS self-diagnosis, and if okay, end test.
3. On Maxima and 300ZX models, confirm idle switch operation. Turn ignition switch to "ON", and check voltage between 20-pin connector terminal No. 18 and 16-pin connector terminal No. 25. Battery voltage should be present. Voltage will change to zero volts when engine speed is reducing from 900 RPM. If incorrect, adjust idle switch so that the switch turns on at engine idle A 250 RPM.
4. Disconnect ECU 20-pin and 16-pin connectors. Check for continuity between terminals No. 18 and 25. (Scheme 28)and (Scheme 29). With the accelerator pedal free, resistance should be zero ohms. With the accelerator pedal depressed, resistance should be infinite. If okay, replace the ECU. If not okay, go to next step.
5. Check throttle valve switch. Disconnect throttle valve switch harness connector. Check the throttle valve switch for continuity between terminals No. 25 and 18. (Scheme 38) Continuity should exist with the throttle valve at idle, and should not exist when valve is slightly open. If not, replace throttle valve switch. IDLE SPEED SPECIFICATIONS Application RPM Maxima & 300ZX 650-750
6. Check harness for insulation. Resistance should be infinite between throttle valve switch harness connector terminals No. 18 and 25, between 18 and ground, and between 25 and ground. Connect harness terminals No. 18 and 25 with a lead wire and check for continuity between 20-pin connector terminal No. 18, and 16-pin connector terminal No. 25. If no good, repair or replace harness. If okay, replace ECU.

NEUTRAL/PARK SWITCH TEST - CODE 24

On 300ZX models, check harness for continuity. If no good, repair harness. If okay, check neutral/park switch. With plunger depressed there should be no continuity. In free position there should be continuity. If no good, replace switch. If okay, replace ECCS control unit.

LOAD SIGNAL TEST - CODE 31

Disconnect 16-pin connector. Turn ignition switch to "ON" and measure voltage between terminal No. 22 and ground when any of the following load switches are turned on: power steering oil pressure switch, heater/air conditioner switch, headlamp switch, rear defogger switch, or radiator fan switch. Battery voltage should be present. If ok, replace the ECU. If not okay, check load system operation, and the harness between ECU and diodes, and harness between diodes and switches. If not okay, replace/repair. If okay, replace ECU.

START SIGNAL CHECK - CODE 32

Check starting system. If okay, disconnect starter motor "S" terminal. Disconnect 20-pin connector and measure voltage between terminal No. 9 and ground. There should be battery voltage. If not, repair harness. If okay, replace ECCS control unit.

DETONATION SENSOR - CODE 34 (TURBOCHARGED MODELS)

On turbocharged models, disconnect detonation sensor harness connector. Start engine and increase engine speed while checking ignition timing. Check if ignition timing retards by 5 degrees when engine speed increases more than 2000 RPM. If not, replace ECCS control unit. If okay, check harness for continuity. If okay, replace detonation sensor.

FUEL TEMPERATURE SENSOR TEST - CODE 41

1. On Maxima and 300ZX models, disconnect fuel temperature sensor. Measure the resistance of the fuel temperature sensor, and compare with SENSOR TEMPERATURE table.
2. Disconnect 20-pin connector and measure the resistance between terminal No. 15 and ground. (Scheme 33) Resistance should be infinite. Connect the connector and ground with a lead wire. Measure the resistance between terminal No. 15 and ground. Resistance should not exist. SENSOR TEMPERATURE/RESISTANCE RELATIONSHIP Temperature Ohms 14°F (10°C) 7000-11400 68°F (20°C) 2100-2900 122°F (50°C) 680-1000 176°F (80°C) 260-390 212°F (100°C) 180-200
3. If resistance readings are okay, replace ECCS control unit. If not okay, check harness for continuity and repair if necessary. If harness is okay, measure resistance of fuel temperature sensor.
4. If sensor temperature resistance readings are okay, replace ECCS control unit. If readings are not as specified, replace fuel temperature sensor and pressure regulator as an assembly.

EGR CONTROL VALVE CHECK

1. On Maxima and 300ZX models, warm up engine. Check movement of EGR valve diaphragm by keeping engine speed between 900 RPM and 3200 RPM. With engine cold, diaphragm should not move. While engine is hot, diaphragm should move upwards. If not okay, go to step 3). If okay, go to next step.
2. Check EGR valve for operation. The EGR control solenoid should be on, and the EGR system should be off under the following conditions: engine starting; throttle valve switch on; low engine temperature; high engine temperature; engine speed below 900 RPM and above 3200 RPM. If okay, end test. If not okay, check the throttle valve switch, cylinder head temperature sensor, ignition signal, and the starting system.
3. Check EGR vacuum. Disconnect vacuum hose at EGR valve. Check if a vacuum appears when keeping engine speed at 900 RPM to 3200 RPM. Stop engine. If not okay, go to next step. If okay, check EGR control valve. Apply 3.94-4.33 in. Hg of vacuum to the EGR control valve. The valve should be fully open. If okay, restart inspection, if not, replace EGR valve, and start test again.
4. Check vacuum hose for proper connection, distortion, plugging, or breaks. If not okay, replace. If okay, check solenoid valve. Check EGR control solenoid valve for continuity. Resistance at the valve connector should be approximately 30 ohms. Check EGR control solenoid for operation. (Scheme 40) If not okay, replace EGR control solenoid valve. If okay, check battery voltage.
5. Disconnect EGR control solenoid valve harness connector and check voltage with ignition switch in the "ON" position. Voltage at connector should be zero volts when ignition switch is in the "OFF" position, and 12 volts when switch is turned to the "ON" position. If not okay, check harness between the solenoid and ECU, and battery source for ECU. Refer to BATTERY SOURCE & GROUND test. If okay, check harness between ECU terminal No. 4 and the solenoid valve.
6. Disconnect ECU 20-pin connector, and check for continuity between terminal No. 4 and ground while jumping EGR control solenoid harness connector to ground. (Scheme 40) Resistance should be zero ohms. If not okay, repair or replace solenoid harness. If okay, check throttle valve switch, cylinder head temperature sensor, ignition signal and starting system. If okay, replace ECU.

EGR Control Valve Operation. Scheme 40

AIR REGULATOR CHECK

1. On Maxima and 300ZX, visually inspect air regulator shutter for operation. Shutter should be half-open when engine is cold, and fully open when engine is warm. Check air regulator for continuity.
2. Disconnect air regulator harness connector. Resistance should be 70 ohms across leads of connector. If not, replace regulator. If okay, check battery voltage.
3. Turn ignition switch to the "ON" position and measure the voltage from one connector lead to ground. Battery voltage should be present. If not okay, check ignition switch, battery, harness between ignition switch and air regulator, and start test again. If voltage was present, check harness between ECU terminal No. 16 and air regulator.
4. Disconnect ECU 20 -pin connector and check continuity between terminal No. 16 and ground. Resistance should be infinite. If not, repair or replace harness. If insulation is okay, connect air regulator harness connector and ground with a lead wire, then check for the resistance between terminal No. 16 and ground. Resistance should be zero ohms. If okay, replace ECU.
5. Disconnect 20-pin connector. Check voltage between terminal No. 16 and ground when ignition is in the "ON" position. see scheme 24 If there is battery voltage, replace ECCS unit. If not, check harness and repair if necessary. If harness is okay, check air regulator. see scheme 24: ECCS 20-Pin Connector Terminal Locations
6. Check for continuity between the 2 terminals of the connector. Resistance should be 70 ohms. If not okay, replace air regulator. If okay, check EFI harness.
7. Turn ignition switch to the "ON" position, and measure voltage at the connector of EFI harness. Battery voltage should be present between connector and ground. If not okay, repair or replace harness. If okay, replace ECCS.

INJECTOR TEST

1. On Maxima and 300ZX models, check each injector for continuity. Resistance should be 3 ohms. If not, replace injector. If okay, check battery voltage at each injector.
2. Disconnect ECU 15-pin connector. Measure voltage between injector harness terminal and ground with the ignition to the "OFF" position. Voltage should be battery voltage. If not, check harness and fusible link. If okay, check ECU harness.
3. Check harness between ECU and connectors for continuity. Connect a lead jumper wire between injector connector terminals. Check voltage between 15-pin connector terminals No. 101, 102, 103, 104, 105, 106 and 114 and ground. If battery voltage is not present, repair or replace harness. If voltage is present, replace ECU.

BATTERY SOURCE & GROUND TEST

1. On Maxima and 300ZX models, verify that diagnosis mode selector on the ECCS control unit is turned fully counterclockwise. Turn ignition on and make sure that Red and Green inspection lamp on the control unit stay on. If they stay on, test is complete.
2. If not, disconnect ECU 15-pin and 16-pin connectors. Check for continuity between terminals No. 28, 36, 107, 109, 112 and 113 and ground. Resistance should be zero ohms. If not, check that the ground terminal is securely mounted. If it is, replace harness. If it is not securely mounted, re-mount.
3. If resistance at ECU terminals was as specified, check battery voltage. Securely connect ECU 15-pin and 16-pin connectors. Turn ignition switch to the "ON" position and measure the voltage between terminals No. 27 and 35 and ground. Battery voltage should be read. If okay, inspection ends. If not okay, check EFI control relay.
4. Measure the voltage at terminal No. 6 of 20-pin connector for 6 seconds when ignition switch is turned to "OFF" from the "ON" position. Voltage should be 12 volts when ignition is turned to the "OFF" position, and zero volts when ignition is turned to the "ON" position. If not okay, check terminal polarity of battery, check harness between ECU No. 6 and EFI relay.
5. Check for continuity at EFI relay. Relay continuity should be as stated in the «EFI RELAY CONTINUITY»(/nissan/300zx/z31-1983-1989/remont/testing-diagnostics/#ecc-cec-system) table. If okay, check the harness between ECU terminals No. 27 and 35 and EFI relay. (Scheme 37) If not, replace EFI relay.

EFI RELAY CONTINUITY

EXHAUST GAS SENSOR TEST

1. On Maxima and 300ZX models, disconnect 15-pin connector and check voltage between terminal No. 115 and ground when ignition is in the "ON" position. (Scheme 41) If there is battery voltage, test is complete. If not, measure the resistance between terminals of exhaust gas sensor heater connector. Resistance should be between 5.0-6.0 ohms. If okay, check harness. If not okay, replace exhaust gas sensor.
2. If resistance across sensor was okay, turn ignition switch to the "ON" position and measure the voltage at the harness connector. Battery voltage should be present. If not, check EFI relay, harness between EFI relay and exhaust gas sensor, and harness between EFI relay and battery. If voltage was okay, check harness between ECU terminal No. 115 and exhaust gas sensor. Jump harness to ground with a lead wire, and measure resistance between ECU 15-pin connector terminal No. 115 and ground. Continuity should exist. If not, repair or replace. If resistance was not present, replace ECU.

AUXILIARY AIR CONTROL VALVE TEST

1. On 300ZX Turbo, check voltage between 20-pin and 16-pin connector terminals No. 2 and 28, and between No. 2 and 36, with connectors connected to the control unit. Battery voltage should be present with ignition switch turned to the "ON" position. If battery voltage is present, test is complete. If not present, check harness and repair if necessary. If okay, check fuel pump relay.
2. Check for continuity between terminals No. 1-2 and 3-4 on fuel pump relay connector. There should be continuity between terminals No. 1-2 and no continuity between terminals No. 3-4. Apply 12 volts to terminals No. 1-2. There should now be continuity between terminals No. 3-4. see scheme 24and (Scheme 41). If no good, replace relay. If okay, go to next step.
3. Check AAC valve for continuity between terminals. Continuity should exist. If there is no continuity, replace AAC valve.

IDLE-UP SOLENOID VALVE TEST

1. Check idle-up solenoid valve for continuity. Resistance between the terminals of the solenoid valve connector should be 30 ohms. If not, replace. If okay, check EFI harness for continuity and main harness for battery source. Check EFI relay. Repair or replace as needed.
2. On Maxima, check system operation. Warm engine, and run at idle. Turn on the headlamp switch and observe engine speed. On manual transmission models, engine speed is increased. On automatic transmission models, engine speed is reduced when disconnecting idle up solenoid valve harness connector (in "D" position).
3. Check load signals. Perform self-diagnosis. Check solenoid valve for continuity. (Scheme 41) Resistance across valve connector terminals should be 30 ohms. If not okay, replace idle-up solenoid valve.
4. Check for battery source. Battery voltage should be present between valve connector and ground when ignition switch is in the "ON" position. If okay, go to next step. If not, check harness between solenoid valve and fuse block and ignition relay and switch.
5. Check harness between ECU terminal No. 2 and solenoid valve. Disconnect ECU 20-pin connector. Connect harness connector and ground with a lead wire. Check continuity between ECU terminal No. 2 and ground. Resistance should be zero ohms. If not, repair or replace. If okay, replace ECU.
6. On 300ZX, check for battery voltage between terminals No. 2 and 28, and 2 and 36 with the 16-pin and 20-pin connectors connected to the control unit. If okay, end test. If not okay, check harness for continuity.
7. Check EFI relay for continuity. Continuity should exist between relay connector terminals No. 1 and 2, and between terminals No. 3 and 4 with 12 volts applied between terminals No. 1 and 2. If not okay, replace EFI relay. If okay, check idle-up solenoid for continuity between the terminals of each connector.

Checking Idle-Up Solenoid Valve Continuity. Scheme 41

AIR INJECTION VALVE CONTROL TEST

1. On Maxima and 300ZX models, check system operation. Disconnect cylinder head temperature sensor harness connector and connect a resistor (2500-ohm) across the terminals of cylinder head temperature sensor harness connector.
2. Start engine and check whether the AIV valve operates by listening to the operating sound. If okay, disassemble AIV case and check AIV control valve and reed valves for binding or damage. Check cylinder head temperature sensor. If okay, test is complete. Replace malfunctioning part.
3. Check AIV control solenoid valve for continuity. Resistance should be 30 ohms across terminals of valve connector. Check AIV control solenoid valve for operation. If not okay, replace the solenoid valve.
4. Check for battery voltage between harness connector and ground when the ignition switch is turned to the "ON" position. Battery voltage should be present. If not, check battery voltage and ground for ECU, and harness between EFI relay and the solenoid valve.
5. Check harness for continuity. Jump with a wire lead harness connector to ground. Measure resistance between ECU terminal No. 14 and ground. Resistance should be zero ohms. If not, repair or replace harness. If okay, replace ECU.
6. If voltage readings were not okay, check harness continuity between AIV solenoid valve and ECU. Stop engine. Disconnect AIV solenoid valve harness connector. Disconnect 20-pin connector from ECU. Check resistance between terminal B of valve harness connector, and ECU terminal No. 20. Resistance should be zero ohms.

PRESSURE REGULATOR SOLENOID VALVE TEST

1. Disconnect cylinder head temperature sensor harness connector and connect a lead wire between the terminals of cylinder head temperature sensor harness connector.
2. Disconnect vacuum hose between pressure regulator and solenoid valve. Start engine and make sure that vacuum does not exist for 3 minutes. If okay, test is complete. If not, go to next step.
3. Confirm that ignition switch is in the "OFF" position, and check for continuity between regulator harness connector terminals No. 80, 83 and 85 and ground. Turn ignition switch to the "ON" position, and measure voltage between harness terminals No. 81 and 84 and ground. Battery voltage should be present. Disconnect starter motor "S" terminal. Turn ignition switch to "START", and measure voltage between harness terminal No. 82 and ground. Battery voltage should be present.
4. On all, check pressure regulator control solenoid valve for continuity. Resistance between terminals of solenoid valve connector should be 30 ohms on Maxima and 300ZX models.
5. On Maxima and 300ZX models, check pressure regulator control solenoid valve for operation. If not okay, replace pressure regulator control valve. If okay, check for battery voltage between solenoid valve harness connector and ground. Battery voltage should be present when ignition switch is in the "ON" position.
6. Check harness between solenoid valve and ECU terminal. Jump solenoid harness connector to ground with a lead wire. Measure continuity between 20-pin connector terminal No. 19 and ground. Resistance should be zero ohms. If not, repair or replace solenoid valve. If continuity exists, replace ECU.

ECCS Wiring Diagram (Maxima). Scheme 42

ECCS Wiring Diagram (300ZX & 300ZX Turbo). Scheme 43

See also:
• COOLANT SENSOR TEMPERATURE/RESISTANCE RELATIONSHIP