Engine Controls - System/component Tests — Nissan Stanza III (1990-1992)

INTRODUCTION

Before testing separate components or systems, perform procedures in BASIC TESTING article in the ENGINE PERFORMANCE Section. Since many computer-controlled and monitored components set a trouble code if they malfunction, also perform procedures in TESTS W/CODES article in the ENGINE PERFORMANCE Section.

Note. Testing individual components does not isolate shorts or opens. Perform all voltage tests with a Digital Volt-Ohmmeter (DVOM) with a minimum 10-megohm input impedance, unless stated otherwise in test procedure. Use ohmmeter to isolate wiring harness shorts or opens.

Note. To identify ECU terminals, see WIRING DIAGRAMS article in the ENGINE PERFORMANCE Section.

POWER VALVE CONTROL SOLENOID

Remove vacuum lines and electrical connector from solenoid. Remove solenoid from vehicle. Connect hand-held vacuum pump to middle vacuum port of solenoid and apply vacuum. Solenoid should hold vacuum. Apply battery voltage between solenoid terminals. Vacuum should release.

SURGE TANK & ONE-WAY CHECK VALVE

Apply vacuum to surge tank located on firewall. Vacuum should hold. Apply vacuum to both sides of one-way check valve. Valves should hold vacuum in only one direction. Ensure valve is installed with holding side away from vacuum source.

SWIRL CONTROL VALVE SYSTEM

The Stanza swirl control valve actuator and solenoid are located next to distributor.

SWIRL CONTROL VALVE

Valve should close when vacuum is applied to swirl control valve actuator and should open when vacuum is not applied.

SWIRL CONTROL VALVE SOLENOID

Remove vacuum lines and electrical connector from solenoid. Remove solenoid from vehicle. Connect hand-held vacuum pump to middle vacuum port of solenoid. Apply battery voltage to solenoid. Ensure correct polarity is used or damage to solenoid may result. Apply vacuum. As battery voltage is applied and removed from solenoid, vacuum should alternately bleed from remaining 2 ports.

ELECTRONIC CONTROL UNIT (ECU) POWER & GROUND SIGNALS

See appropriate ECU POWER SOURCE & GROUND diagnostic chart.

ENGINE SENSORS & SWITCHES

Note. For location and identification of ECU terminals, see WIRING DIAGRAMS article.

AIRFLOW METER

Ensure there is no dust or foreign material in hot wire air passage. Faults in the airflow meter circuit should set a trouble code. If Code 12 is set, go to CODE 12 diagnostic procedures in TESTS W/CODES article. Also see AIRFLOW METER VOLTAGE TEST table.

Application	ECU Terminal (2)	Volts
Stanza	16	1.0-3.0
(1) Measure voltage between ground and indicated ECU terminal. Voltage should increase with an increase in airflow (RPM). DO NOT run engine at high RPM under no load. (2) To identify ECU terminals, see WIRING DIAGRAMS article.

(1)	Measure voltage between ground and indicated ECU terminal. Voltage should increase with an increase in airflow (RPM). DO NOT run engine at high RPM under no load.

(2)	To identify ECU terminals, see WIRING DIAGRAMS article.

AIRFLOW METER VOLTAGE TEST (1)

A/C SWITCH

To check A/C switch, measure voltage between ground and specified ECU terminal and condition. See A/C SWITCH VOLTAGE TEST table.

Application	ECU Terminal (2)	Volts
Stanza	41	(3) Zero, (4) 11-14
(1) Measure voltage between ground and indicated ECU terminal. (2) To identify ECU terminals, see WIRING DIAGRAMS article. (3) With engine running both and A/C and blower switches on. (4) With engine running and A/C off switch.

(1)	Measure voltage between ground and indicated ECU terminal.

(2)	To identify ECU terminals, see WIRING DIAGRAMS article.

(3)	With engine running both and A/C and blower switches on.

(4)	With engine running and A/C off switch.

A/C SWITCH VOLTAGE TEST (1)

AIR TEMPERATURE SENSOR

Air temperature sensor is a component part of mass airflow sensor. Measure sensor resistance across sensor terminals. At 68°F (20°C), resistance should be about 2100-2900 ohms. At 176°F (80°C), resistance should be about 270-380 ohms. Check sensor voltage values against values in AIR TEMPERATURE SENSOR VOLTAGE TEST table. Replace sensor if voltages are not within specifications.

Temperature °F (°C)	Volts
68 (20)	1.0-1.5
176 (80)	.3
(1) With engine running, measure voltage between ground and ECU terminal No. 26.

(1)	With engine running, measure voltage between ground and ECU terminal No. 26.

AIR TEMPERATURE SENSOR VOLTAGE TEST (1)

ENGINE (COOLANT) TEMPERATURE SENSOR

Disconnect engine (coolant) temperature sensor connector. Measure resistance across sensor terminals. Check sensor resistance values against values in ENGINE (COOLANT) TEMPERATURE SENSOR RESISTANCE TEST table. Replace sensor if values are not as specified.

Temperature °F (°C)	Ohms
68 (20)	2100-2900
176 (80)	300-330
(1) Measure resistance across sensor terminals.

(1)	Measure resistance across sensor terminals.

ENGINE (COOLANT) TEMPERATURE SENSOR RESISTANCE TEST (1)

EXHAUST GAS (OXYGEN) SENSOR

If fault is present in oxygen sensor circuit, Code 33 will be set in ECU memory. If Code 33 is set, go to CODE 33 diagnostic procedures in TESTS W/CODES article.

Condition	Volts
Lean	.1
Rich	1.0
(1) With engine running at normal operating temperature, measure voltage between oxygen sensor connector terminal and ground.

(1)	With engine running at normal operating temperature, measure voltage between oxygen sensor connector terminal and ground.

EXHAUST GAS (OXYGEN) SENSOR VOLTAGE TEST (1)

EXHAUST GAS TEMPERATURE SENSOR (CALIFORNIA)

Place exhaust gas temperature sensor in boiling water at 212°F (100°C). Resistance at 212°F (100°C) should be 76,770-93,830 ohms. As temperature increases, sensor resistance should decrease. Check sensor voltage values against values in EXHAUST GAS TEMPERATURE SENSOR VOLTAGE TEST table. Replace sensor if values are not as specified.

Pin No.	Volts w/EGR Closed	Volts w/EGR Open
8	1.0 or More	0-1.0
(1) With engine running, measure voltage between ground and indicated ECU terminal.

(1)	With engine running, measure voltage between ground and indicated ECU terminal.

EXHAUST GAS TEMPERATURE SENSOR VOLTAGE TEST (1)

NEUTRAL/INHIBITOR SWITCH

Check switch voltage values against values in the NEUTRAL/INHIBITOR SWITCH TEST table. Replace switch if values are not as specified. Also, see appropriate NEUTRAL/INHIBITOR SWITCH or NEUTRAL SWITCH & A/T CONTROL diagnostic chart.

Terminal No.	Volts In Park/Neutral	Volts In All Other Positions
35	Zero	6.0-7.0
(1) Turn ignition on. With transmission in specified position, check voltage between ground and indicated ECU terminal.

(1)	Turn ignition on. With transmission in specified position, check voltage between ground and indicated ECU terminal.

NEUTRAL/INHIBITOR SWITCH TEST (1)

POWER STEERING OIL PRESSURE SWITCH

Switch is attached to power steering high pressure hose. Signal is used by ECU to help control idle speed. Check resistance between switch terminals. Resistance should be 2-3 ohms.

Check voltage at appropriate ECU terminal with engine idling and steering wheel in straight ahead then measure voltage again while turning steering wheel side-to-side. See POWER STEERING OIL PRESSURE SWITCH TEST table and the WIRING DIAGRAMS article to identify proper ECU terminal for testing.

For diagnosing power steering oil pressure switch system, see appropriate POWER STEERING OIL PRESSURE SWITCH diagnostic chart.

ECU Terminal	(1) Volts	(2) Volts
43	8-9	Zero
(1) With engine running and steering wheel straight ahead. (2) With engine running and turning steering wheel side-to-side.

(1)	With engine running and steering wheel straight ahead.

(2)	With engine running and turning steering wheel side-to-side.

POWER STEERING OIL PRESSURE SWITCH TEST

THROTTLE POSITION SENSOR (TPS) & IDLE SWITCH

Throttle position sensor and idle switch are a combined assembly located on side of throttle body. See ADJUSTMENTS article in the ENGINE PERFORMANCE Section for adjustment procedures. Check sensor voltage values against values in THROTTLE POSITION SENSOR VOLTAGE TEST table. Replace sensor if values are not as specified in the table.

Application	Terminal No.	Volts
Stanza	20	.4-4.0
(1) Turn ignition on. Measure voltage between ground and indicated ECU terminal. Observe voltage while opening and closing throttle valve.

(1)	Turn ignition on. Measure voltage between ground and indicated ECU terminal. Observe voltage while opening and closing throttle valve.

THROTTLE POSITION SENSOR VOLTAGE TEST (1)

VEHICLE SPEED SENSOR

Remove vehicle speed sensor from transmission. Connect DVOM across sensor terminals. Turn vehicle speed sensor by hand and note voltage. Reading should be .5 volt (alternating current). If reading is not as specified, replace sensor

RELAYS

A variety of relays are used and can be tested 2 different ways. The following relays can be tested using an ohmmeter and remotely supplied power and ground circuits

Fuel pump relay
Main relay
Radiator/condenser (cooling) fan relay
Mixture heater relay
Neutral/park relay.

Safety relays can be tested using an ohmmeter, voltmeter and remotely supplied power and ground circuits. All testing procedures require proper identification of relay internals. See WIRING DIAGRAMS article.

Except Safety Relay

Turn ignition on. Ensure power to relay exists. Turn ignition off. Disconnect connector from relay being tested. Using ohmmeter, check for relay winding continuity across appropriate relay terminals. See WIRING DIAGRAMS article to identify proper relay terminals (wire colors) for testing. Energize relay and check continuity of relay output circuit.

EXAMPLE: Typical Fuel Pump Relay

Turn ignition on. Ensure battery voltage exists at Blue wires of safety relay and fuel pump relay. (Scheme 19) If battery voltage is not present at both Blue wires, check for a blown 10-amp power fuse or an open circuit between fuse and relays.
Turn ignition off. Unplug fuel pump relay. Check for continuity across Blue wire and Blue/White wire terminals. If continuity does not exist, relay is defective. If continuity exists, Black wire terminals. Energize relay by applying battery voltage to Blue wire terminal and ground to Blue/White wire terminal. Ensure continuity exists while relay is energized.

Scheme 19

Safety Relay

Turn ignition on and ensure power to relay exists. Turn ignition off. Disconnect safety relay connector. Using an ohmmeter, check one-way internal diode in safety relay by checking for continuity in both directions. Energize relay and check for voltage signal on relay output circuit.

EXAMPLE: Typical Safety Relay

Turn ignition on. Using a voltmeter, check for battery voltage at Blue wire of safety relay. (Scheme 19) If voltage is not present, check for blown 10-amp fuse or open circuit between fuse and relay.
Turn ignition off. Disconnect safety relay connector. Using ohmmeter, check for continuity across relay's Black wire and Blue wire terminals. Reverse ohmmeter leads. Continuity should only exist in one direction. Connect voltmeter positive lead to Red/Blue wire terminal. Connect negative voltmeter lead to Black wire terminal. Apply battery voltage to Blue wire terminal and ground to Black wire terminal. Voltmeter should show battery voltage while relay is energized.

AIR INJECTION CONTROL VALVE SOLENOID

See AIR INJECTION CONTROL VALVE SOLENOID under AIR INJECTION EMISSION SYSTEMS & SUB-SYSTEMS .

EGR CONTROL SOLENOID

See EXHAUST GAS RECIRCULATION (EGR) under AIR INJECTION EMISSION SYSTEMS & SUB-SYSTEMS .

FAST IDLE CONTROL DEVICE (FICD) SOLENOID

Apply battery voltage to solenoid terminals. Solenoid should operate. Also check solenoid plunger for sticking and check for broken spring.

See AIR INDUCTION POWER VALVE SYSTEMS .

See SWIRL CONTROL VALVE SYSTEM under AIR INDUCTION POWER VALVE SYSTEMS. Also, see appropriate SWIRL CONTROL VALVE diagnostic chart.

FUEL PRESSURE

For fuel pressure procedures and specifications, see FUEL PRESSURE under FUEL SYSTEM in BASIC TESTING article.

FUEL PRESSURE REGULATOR

Relieve fuel pressure from system. Connect fuel pressure gauge between fuel filter and fuel tube. Remove hose from fuel pressure regulator and plug intake manifold. Connect hand-held vacuum pump to pressure regulator. Turn engine on and gradually apply vacuum to regulator. Fuel pressure should decrease as vacuum increases. Compare fuel pressures to regulated pressure values listed in FUEL PRESSURE table in BASIC TESTING article. If pressures are not as specified, replace fuel pressure regulator.

FUEL PUMP

If fuel pump does not run, disconnect fuel pump connector. Provide ground and battery voltage to fuel pump connector terminals. See WIRING DIAGRAMS article to identify fuel pump connector terminals (wire colors). If pump runs, see RELAYS under RELAYS & SOLENOIDS for testing, or repair open or short in harness between relay and pump. If pump does not run, replace fuel pump. Also, see appropriate FUEL PUMP diagnostic chart.

FUEL PUMP RELAY

See RELAYS under RELAYS & SOLENOIDS.

START SIGNAL

Start (ON-OFF switch) signal is used for ECU control of fuel pump. See appropriate START SIGNAL diagnostic chart.

FEEDBACK SYSTEM

Stanza models use a single Red LED. Start engine and warm to operating temperature. Ensure idle speed and timing are adjusted to specification. Increase engine speed to about 2000 RPM for 2 minutes under no-load condition; enter self-diagnostic Mode II and monitor Red LED on ECU.
Red LED should flash a minimum of 5 times every 10 seconds. If Red LED does not respond as described, check idle mixture (CO percentage level). See ADJUSTMENTS article. If idle mixture adjustment does not affect LED operation, check fuel pressure regulator, airflow meter, injector(s), engine (coolant) temperature sensor or ECU.

FUEL INJECTOR

See appropriate INJECTOR MALFUNCTION diagnostic chart.

Start (ON-OFF switch) signal is used for ECU control of injector(s). See appropriate START SIGNAL diagnostic chart.

Application	Ohms
Stanza	10-15

INJECTOR RESISTANCE SPECIFICATIONS

AIR REGULATOR

See appropriate AIR REGULATOR diagnostic chart. Measure resistance across regulator valve terminals. Resistance should be about 70-80 ohms.

AUXILIARY AIR CONTROL (AAC) SOLENOID/VALVE

AAC valves on all other models are solenoids. Ensure AAC winding resistance is within specification. See AAC WINDING RESISTANCE table.

Terminals No.	Ohms @ 68°F (20°C)
Stanza	10

AAC WINDING RESISTANCE

FAST IDLE CONTROL DEVICE (FICD)

See FAST IDLE CONTROL DEVICE (FICD) SOLENOID under SOLENOIDS.

Start (ON-OFF switch) signal is used for ECU control of air regulator. See appropriate START SIGNAL diagnostic chart.

IGNITION SYSTEM

For ignition system testing, see BASIC TESTING article.

Start (ON-OFF switch) signal is used for ECU control of ignition system. See appropriate START SIGNAL diagnostic chart.

TIMING ADVANCE SYSTEM

Ignition timing advance is controlled by the ECU based upon sensor input signals reflecting ignition timing needs. If timing problems are experienced, inspect input signals for proper operation. See appropriate ECU pin voltage chart in PIN VOLTAGE CHART S article in the ENGINE PERFORMANCE Section. Inputs which help control timing include the following

Crank angle sensor
Airflow meter
Engine (coolant) temperature
Idle switch in idle position
Ignition switch crank signal
Battery voltage.

DETONATION RETARD OPERATION

Problems with the detonation retard circuit should cause Code 34 to be set. If Code 34 is present, see CODE 34 chart in TESTS W/CODES article. Check knock sensor wire for open or short to ground. Check knock sensor shield ground wire for continuity to ground. Check routing of knock sensor wire. Wire should not be routed close to spark plug wires or high output accessories.

AIR INJECTION VALVE

Apply vacuum to Air Injection Valve (AIV) vacuum motor. (Scheme 20) Apply air to air cleaner side of AIV and make sure air only flows toward exhaust manifold side. Also see appropriate AIR INJECTION VALVE diagnostic chart.

Scheme 20

Scheme 20: AIR INJECTION VALVE

Remove vacuum lines and electrical connector from solenoid. Remove solenoid from vehicle. Connect hand-held vacuum pump to middle vacuum port "B" of solenoid. Apply battery voltage to solenoid. (Scheme 21) Ensure correct polarity is used or damage to solenoid may result. Apply vacuum. As battery voltage is applied and removed from solenoid, vacuum should alternately bleed from remaining 2 ports.

Scheme 21

Scheme 21: AIR INJECTION CONTROL VALVE SOLENOID

FUEL TANK VACUUM RELIEF VALVE

Wipe valve housing clean. Find means to inhale air through cap. A slight resistance accompanied by clicks indicates vacuum relief valve is okay. By further inhaling air, resistance and clicks should disappear. If valve is clogged or if no resistance is felt, replace fuel tank filler cap.

Scheme 22

Scheme 22: FUEL VAPOR VENT LINE

Check all hoses and fuel filler cap for leaks. Disconnect fuel tank vapor hose at canister. Attach "T" fitting, manometer, and shutoff valve to hose. (Scheme 22)
Slowly apply air pressure to open shutoff valve until manometer indicates 15 3/4" (400 mm) water. Close shutoff valve. Remove air supply.
Fuel tank and hoses should hold this pressure within 1" (25 mm) of water for 2 1/2 minutes. If not, repair or replace components as necessary.
If pressure holds for 2 1/2 minutes, remove fuel filler cap. Ensure pressure drops. If not, check hoses and lines for obstructions.

CARBON CANISTER

Remove hoses from carbon canister. Blow air into canister ports as shown. (Scheme 23) Air should pass through purge and vent lines, but should not pass through vacuum lines.

Scheme 23

Scheme 23: CARBON CANISTER

FUEL CHECK VALVE

Disconnect hoses from fuel check valve. Apply air on fuel tank side of valve. Resistance should be felt and a portion of airflow should be directed toward carbon canister. Repeat test on carbon canister side of valve. Air should flow freely through valve. If valve does not function as stated, replace check valve.

VACUUM RELIEF FILLER CAP

Wipe cap clean. Apply vacuum from tank side. Slight resistance should be felt and the cap should make distinct clicking noises. As vacuum increases, resistance should decrease and clicking noise should stop. If valve is plugged or no resistance is felt, replace cap as an assembly.

EGR CONTROL SYSTEM

See appropriate EGR CONTROL and EGR FUNCTION diagnostic charts.

EGR BACKPRESSURE TRANSDUCER

Plug one port of the EGR backpressure transducer (EGR-BPT). (Scheme 24)and (Scheme 25). Connect hand-held vacuum pump to remaining EGR vacuum port and apply vacuum. Apply pressure to bottom port. Check for leaks. If leak is present, replace BPT valve.

Scheme 24

Scheme 24: EGR BACKPRESSURE TRANSDUCER

Scheme 25

EGR VALVE

Apply vacuum to EGR valve using a hand-held vacuum pump. EGR control valve should be fully open. Replace EGR valve if operation is not as specified. (Scheme 26)

Scheme 26

Scheme 26: EGR VALVE

EGR CONTROL SOLENOID (2-PORT)

Remove vacuum lines and electrical connector from solenoid. Remove solenoid from vehicle. Connect hand-held vacuum pump to either vacuum port of solenoid. Apply battery voltage to solenoid. Ensure correct polarity is used or damage to solenoid may result. Apply vacuum. As battery voltage is applied and removed from solenoid, vacuum should alternately bleed/hold from remaining port. Replace solenoid if operation is not as specified.

EGR CONTROL SOLENOID (3-PORT)

Start (ON-OFF switch) signal is used for ECU control of EGR control solenoid. See appropriate START SIGNAL diagnostic chart.

POSITIVE CRANKCASE VENTILATION (PCV)

Run engine at idle. Remove ventilation hose from PCV valve. If valve is working properly, a hissing noise should be heard from hose and a strong vacuum should be felt immediately when finger is placed over valve inlet. If not, check hose and hose connections for leaks or obstructions. Repair or replace as necessary.

MISCELLANEOUS CONTROLS

Note. Although some of the controlled devices listed here are not technically engine performance components, they can affect driveability if they malfunction.

RADIATOR (COOLING) FAN MOTOR

The ECU performs on-off control and low/high speed control of the radiator (cooling) fan according to vehicle speed, engine temperature, and A/C on signal. All models use 2 or more cooling fan relays and 2 fan motors.

RADIATOR (COOLING) FAN CONTROL RELAY(S)

See RELAYS under RELAYS & SOLENOIDS. Also, see appropriate table under RADIATOR (COOLING) FAN CONTROL RELAY OPERATION for relay(s) operation.

CONDENSER (COOLING) FAN CONTROL RELAY (S)

See RELAYS under RELAYS & SOLENOIDS. Also, see CONDENSER (COOLING) FAN CONTROL RELAY OPERATION for relay operation.

RADIATOR (COOLING) FAN CONTROL RELAY OPERATION

Engine Coolant Temp.°F (°C)	Cooling Fan Speed (1)	Relay No. (Off or On)
W/Evaporator Outlet Temp. Above 46°F (8°C)
Less Than 201 (94)	(2) High	1 & 2 (On)
203-210 (95-99)	(3) High	1 & 2 (On)
Greater Than 212 (100)	High	1 & 2 (On)
W/Evaporator Outlet Temp. 37-46°F (3-8°C)
Less Than 201 (94)	(2) Low	1 (On), 2 (Off)
203-210 (95-99)	Low	1 (On), 2 (Off)
Greater Than 212 (100)	High	1 & 2 (On)
(1) The radiator (cooling) fan will operate at high speed if engine temperature (coolant) sensor is defective. (2) The radiator (cooling) fan should be off when vehicle speed is greater than 50 MPH. (3) The radiator (cooling) fan should be on low speed when vehicle speed is greater than 50 MPH.

(1)	The radiator (cooling) fan will operate at high speed if engine temperature (coolant) sensor is defective.

(2)	The radiator (cooling) fan should be off when vehicle speed is greater than 50 MPH.

(3)	The radiator (cooling) fan should be on low speed when vehicle speed is greater than 50 MPH.

A/C SWITCH & BLOWER SWITCH ON

Engine Coolant Temp.°F (°C)	Cooling Fan Speed (1)	Relay No. (Off or On)
Less Than 201 (94)	Off	1 & 2 (Off)
203-210 (95-99)	Low	1 (On), 2 (Off)
Greater Than 212 (100)	High	(1 & 2 (On)
(1) The radiator (cooling) fan will operate at high speed if engine (coolant) temperature sensor is defective .