Engine Controls - System/component Tests Nissan Sentra B13

INTRODUCTION

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

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.

ELECTRONIC CONTROL UNIT (ECU) POWER & GROUND CIRCUIT

See appropriate ECU POWER SOURCE & GROUND diagnostic chart.

ENGINE SENSORS & SWITCHES

Note. For ECU connector terminal identification, see PIN VOLTAGE CHARTS article and WIRING DIAGRAMS article.

AIRFLOW METER

Faults in airflow meter circuit may set Code 12. To test system, see CODE 12 diagnostic procedures in TESTS W/CODES article.

1. To test airflow meter, warm engine to operating temperature. Pull rubber protector away from airflow meter connector so terminals can be backprobed. At airflow meter connector, check voltage at Orange wire terminal (NX and Sentra), or White wire terminal (all others).
2. If voltage is not as specified in AIRFLOW METER VOLTAGE TEST table, check for dust or foreign material in hot wire air passage of airflow meter. If air passage is okay, replace airflow meter.

AIRFLOW METER VOLTAGE TEST (1)

AIR CONDITIONER SWITCH

See PIN VOLTAGE CHART S article.

CRANKSHAFT ANGLE SENSOR

Faults in crank angle sensor circuit may set Code 11. To test system, see CODE 11 diagnostic procedures in TESTS W/CODES article. On NX and Sentra, see appropriate CRANK ANGLE SENSOR Flow chart. On all other vehicles, crank angle sensor is part of distributor.

1. To test crank angle sensor, remove crank angle sensor (or distributor). Leave wiring harness connected. On vehicles with distributor, disconnect secondary coil wire from distributor cap, and then connect wire to ground. On all vehicles, turn ignition on.
2. Connect logic probe or DVOM with an analog bar graph function to ground. While slowly rotating sensor shaft by hand, backprobe specified wire terminals of sensor connector. See CRANK ANGLE SENSOR VOLTAGE TEST table.
3. If voltage does not fluctuate between 0 and 5 volts, check for damaged or dirty signal plate in crank angle sensor, and for shorted or open harness. If harness and signal plate are okay, replace crank angle sensor.

Note. It is possible to measure crank angle sensor voltage with a conventional DVOM without bar graph function; however, it may be difficult to determine peak voltage signal due to averaging of signal.

CRANK ANGLE SENSOR VOLTAGE TEST (1)

DETONATION KNOCK SENSOR

Faults in detonation sensor circuit may set Code 34. To test system, see CODE 34 diagnostic procedures in TESTS W/CODES article.

To test sensor, disconnect sensor connector. See the DETONATION SENSOR LOCATION table. Check continuity between ground and sensor connector terminal. If there is no continuity, replace sensor. Check detonation sensor shield ground wire for continuity to ground. Ensure detonation sensor wire is not routed near spark plug wires or high-output electrical accessories.

DETONATION SENSOR LOCATION

ENGINE (COOLANT) TEMPERATURE SENSOR

Faults in engine (coolant) temperature sensor circuit may set Code 13. To test system, see CODE 13 diagnostic procedures in TESTS W/CODES article.

To test sensor, disconnect sensor connector. See ENGINE (COOLANT) TEMPERATURE SENSOR LOCATION table. Measure resistance across sensor connector terminals. If resistance is not as specified in the ENGINE (COOLANT) TEMPERATURE SENSOR RESISTANCE table, replace sensor.

ENGINE (COOLANT) TEMPERATURE SENSOR LOCATION

ENGINE (COOLANT) TEMPERATURE SENSOR RESISTANCE

Note. Exhaust gas (Oxygen) sensor with a heater element is identified by 3-wire connector.

EXHAUST GAS (OXYGEN) SENSOR

Faults in exhaust gas (oxygen) sensor circuit may set Code 33. To test system, see CODE 33 diagnostic procedures in TESTS W/CODES article.

To test HEATER element of exhaust gas sensor, check resistance between outer 2 terminals of 3-wire connector. If resistance is not 3-1000 ohms, replace sensor.

EXHAUST GAS TEMPERATURE SENSOR (CALIFORNIA MODELS)

Faults in exhaust gas temperature sensor circuit may set Code 35. To test system, see CODE 35 diagnostic procedures in TESTS W/CODES article.

To test sensor, place 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. If resistance is not as specified, replace sensor.

NEUTRAL/INHIBITOR SWITCH

To test system, see appropriate NEUTRAL/INHIBITOR SWITCH Flow chart.

POWER STEERING OIL PRESSURE SWITCH

To test system, see appropriate POWER STEERING OIL PRESSURE SWITCH diagnostic chart.

To test switch, disconnect switch connector. Switch is attached to power steering high pressure hose. Check resistance between switch connector terminals. Replace switch if continuity is not as specified in POWER STEERING OIL PRESSURE SWITCH table.

POWER STEERING OIL PRESSURE SWITCH

THROTTLE POSITION SENSOR (TPS) & IDLE SWITCH

Faults in TPS circuit may set Code 43. To test system, see CODE 43 diagnostic procedures in TESTS W/CODES article.

1) To test TPS, disconnect TPS connector. TPS is mounted on side of throttle body. While opening and closing throttle, check resistance across specified wire terminals of TPS connector. See the THROTTLE POSITION SENSOR RESISTANCE TEST table. If resistance value does not change smoothly, replace TPS.

2) If resistance is not as specified, check harness. If harness is okay, adjust TPS. See ADJUSTMENTS article. If resistance is still not as specified after adjustment, replace TPS.

THROTTLE POSITION SENSOR RESISTANCE TEST

VEHICLE SPEED SENSOR (ANALOG INSTRUMENT CLUSTER)

Faults in vehicle speed sensor circuit may set Code 14. To test system, see CODE 14 diagnostic procedures in TESTS W/CODES article.

Note. Instrument cluster connector where continuity is checked is at speedometer end of cluster (without tachometer), or in center of cluster (with tachometer). DO NOT use a self- powered test light to test reed switch; use a DVOM only.

To test sensor, remove instrument cluster (sensor is a reed switch inside cluster). While slowly rotating speedometer drive receptacle, check continuity between terminals of instrument cluster connector. (Scheme 4) If continuity does not exist twice for each rotation, replace speedometer assembly.

VEHICLE SPEED SENSOR (DIGITAL INSTRUMENT CLUSTER)

Faults in vehicle speed sensor circuit may set Code 14. To test system, see CODE 14 diagnostic procedures in TESTS W/CODES article.

To test sensor, remove vehicle speed sensor from trans-mission. While rotating sensor shaft by hand, check AC voltage across sensor connector terminals. If about .5 volt AC is not present, replace sensor.

Scheme 4

RELAYS

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

1. Fuel pump relay
2. Main relay
3. Radiator (cooling) fan relay
4. Mixture heater relay
5. 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 appropriate 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 appropriate 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

1. Turn ignition on. Ensure battery voltage exists at Blue wires of safety relay and fuel pump relay. (Scheme 5) 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.
2. 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, connect ohmmeter leads across Orange wire and 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.

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

1. Turn ignition on. Using a voltmeter, check for battery voltage at Blue wire of safety relay. (Scheme 5) If voltage is not present, check for blown 10-amp fuse or open circuit between fuse and relay.
2. 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.

Scheme 5

Air Injection Control Valve Solenoid

See AIR INJECTION under EMISSION SYSTEMS & SUB-SYSTEMS.

EGR Control Solenoid

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

Valve Timing Control Solenoid (NX 1.6L)

To test system, see VALVE TIMING CONTROL (VTC) Flow chart. To test solenoid, apply battery voltage across solenoid terminals. Replace solenoid if it does not operate.

FUEL DELIVERY

Note. For fuel system pressure testing, see FUEL PRESSURE under FUEL SYSTEM in BASIC TESTING article.

Start Signal

If ECU receives incorrect start (cranking) signal, fuel delivery system may not operate properly. See START SIGNAL Flow chart.

Note. See WIRING DIAGRAMS article to identify appropriate fuel pump connector terminals by wire color.

Fuel Pump

To test system, see appropriate FUEL PUMP Flow chart. On Maxima VG30E engine, a fault in fuel pump circuit may set Code 22. To test system, see CODE 22 diagnostic procedures in TESTS W/CODES article.

To test fuel pump, disconnect fuel pump connector under rear seat (NX and Sentra). At fuel pump connector, check resistance between wire terminals specified in FUEL PUMP RESISTANCE TEST table. If resistance is not as specified, replace fuel pump.

FUEL PUMP RESISTANCE TEST

Fuel Pump Relay

See RELAYS under RELAYS & SOLENOIDS.

If ECU receives incorrect start (cranking) signal, fuel control system may not operate properly. See START SIGNAL Flow chart.

FEEDBACK SYSTEM

Ensure ignition timing and idle speed are adjusted. See ADJUSTMENTS article. Warm engine to operating temperature. Run engine unloaded at 2000 RPM for 2 minutes. Enter self-diagnostic Mode II. See TESTS W/CODES article. If Red LED on ECU (or CHECK ENGINE light) does not flash at least 5 times in a 10-second period, perform IDLE MIXTURE adjustment procedure in ADJUSTMENTS article.

FUEL INJECTOR

See appropriate INJECTOR MALFUNCTION Flow chart.

To test injector, check resistance across injector connector terminals. If resistance is not as specified in INJECTOR RESISTANCE SPECIFICATIONS table, replace injector. If resistance is okay, remove injector. If nozzle is clogged, replace injector.

INJECTOR RESISTANCE SPECIFICATIONS

If ECU receives incorrect start (cranking) signal, idle control system may not operate properly. See START SIGNAL Flow chart.

AIR REGULATOR

See AIR REGULATOR Flow chart. To test air regulator, measure resistance across air regulator connector terminals. If resistance is not about 70-80 ohms, replace air regulator. If resistance is okay, ensure air passage is not obstructed.

AUXILIARY AIR CONTROL (AAC) SOLENOID/VALVE

To test system, see AUXILIARY AIR CONTROL (AAC) Flow chart. To test AAC valve, check resistance across AAC valve connector terminals. If resistance is not 10 ohms, replace AAC valve. Ensure plunger does not stick and plunger spring is not broken.

FAST IDLE CONTROL DEVICE (FICD)

See appropriate FAST IDLE CONTROL DEVICE (FICD) Flow chart. To test FICD solenoid, apply battery voltage across solenoid terminals. If solenoid does not operate, check for sticking plunger or broken spring. If plunger and spring are okay, replace solenoid.

IGNITION SYSTEM

Note. For ignition system testing not covered in this article (ignition coil resistance, etc.), see BASIC TESTING article.

If ECU receives incorrect start (cranking) signal, ignition system may not operate properly. See START SIGNAL Flow chart.

POWER TRANSISTOR

1. Disconnect power transistor connector. (Scheme 6) At power transistor connector, check continuity between the following terminals, noting ohmmeter test lead polarity: "a" (+) and "b" (-) "a" (+) and "c" (-)
2. If there is continuity, replace power transistor. If there is no continuity, reverse ohmmeter test lead polarity and check continuity across terminals listed in previous step. If there is no continuity, replace power transistor. If there is continuity, power transistor is okay.

Scheme 6

TIMING ADVANCE SYSTEM

Ignition timing advance is controlled by the ECU based upon sensor input signals. If timing problems are experienced, inspect input signals for proper operation. See PIN VOLTAGE CHART S article. Inputs that affect timing include the following

1. Crank angle sensor
2. Airflow meter
3. Engine (coolant) temperature sensor
4. Idle switch
5. Start (cranking) signal
6. Battery voltage

DETONATION RETARD OPERATION

Faults in detonation retard circuit may set Code 34. To test system, see CODE 34 diagnostic procedures in TESTS W/CODES article. To test knock (detonation) sensor, see ENGINE SENSORS & SWITCHES.

Air Injection Valve (AIV)

To test system, see AIR INJECTION VALVE Flow chart. To test AIV, apply vacuum to AIV diaphragm. (Scheme 7) Apply light air pressure to air cleaner side of AIV. Air should flow toward exhaust manifold side. Air should NOT flow in opposite direction.

Scheme 7

Note. On some air injection valve control solenoids, port "C" may be a vent that is capped with a filter. Also, if solenoid does not respond as specified, perform test again, considering port "A" as port "B" and vice versa.

To test system, see AIR INJECTION VALVE Flow chart.

1. To test solenoid, disconnect vacuum lines and electrical connector from solenoid. Remove solenoid. Connect hand-held vacuum pump to vacuum port "B" of solenoid. (Scheme 8) Apply vacuum. Vacuum should now be available at port "C", but not at port "A".
2. Apply battery voltage across solenoid connector terminals, ensuring polarity is correct to prevent solenoid damage. Vacuum should now be available at port "A", but not at port "C". Replace solenoid if it does not operate as specified.

Scheme 8

CARBON CANISTER

Remove hoses from carbon canister. Blow air into canister ports as shown. (Scheme 9) Air should pass through vent and purge lines, but should not pass through vacuum lines.

FUEL TANK VACUUM RELIEF VALVE

Valve is located in fuel tank filler cap. Wipe cap clean to prevent inhaling fuel vapors. Find a way to safely apply light vacuum to cap on side of cap that faces fuel tank. A slight resistance accompanied by clicks indicates the valve is okay. By applying more vacuum, resistance should no longer be felt and clicks should no longer be heard. If valve does not operate as specified, replace fuel tank filler cap.

FUEL VAPOR CHECK VALVE

Disconnect hoses from fuel vapor check valve. Apply light air pressure to fitting on side of valve that leads to fuel tank. Resistance should be felt, but some air should flow out of fitting that leads to carbon canister. Apply light air pressure to fitting that leads to carbon canister. Air should flow freely through valve. If valve does not operate as described, replace valve.

Scheme 9

If ECU receives an incorrect start (cranking) signal, EGR control solenoid may not operate properly. See START SIGNAL Flow chart.

EGR CONTROL SYSTEM

See appropriate EGR CONTROL and EGR FUNCTION Flow charts.

EGR BACKPRESSURE TRANSDUCER

Plug one port of EGR backpressure transducer (EGR-BPT) and apply vacuum to other port. (Scheme 10)and (Scheme 11). Vacuum should NOT hold. Apply light pressure to bottom port (DO NOT apply more pressure than is necessary to cause vacuum to hold). If vacuum does not hold with pressure applied, replace EGR-BPT valve.

Scheme 10

Scheme 11

EGR VALVE

Using a hand-held vacuum pump, apply vacuum to EGR valve diaphragm. (Scheme 12) Replace EGR valve if pintle does not open.

Scheme 12

Note. On some EGR control solenoids, port "C" may be a vent that is capped with a filter. Also, if solenoid does not respond as specified, perform test again, considering port "A" as port "B" and vice versa.

1. Disconnect vacuum lines and electrical connector from solenoid. Remove solenoid. Using hand-held vacuum pump, apply vacuum to port "B" of solenoid. (Scheme 11) Vacuum should now be available at port "C", but not at port "A".
2. Apply battery voltage across solenoid connector terminals, ensuring polarity is correct to prevent solenoid damage. Vacuum should now be available at port "A", but not at port "C". Replace solenoid if it does not operate as specified.

POSITIVE CRANKCASE VENTILATION (PCV)

With engine idling, disconnect ventilation hose from PCV valve. If a hissing noise and strong vacuum are not present at hose end, check hose and hose connections for leaks or obstructions. Repair or replace as necessary.

MISCELLANEOUS CONTROLS

Note. For Neutral/inhibitor switch, power steering oil pressure switch and vehicle speed sensor, see ENGINE SENSORS & SWITCHES.

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

RADIATOR (COOLING) FAN CONTROL RELAY(S)

Note. For radiator cooling fan relay testing, see RELAYS under RELAYS & SOLENOIDS.

The ECU controls radiator cooling fan(s) based on vehicle speed, engine coolant temperature and A/C switch position. The following tables list correct cooling fan operation based on certain conditions. See appropriate A/C SWITCH ON or A/C SWITCH OFF table.

If cooling fan does not operate as specified, see RADIATOR (COOLING) FAN CONTROL Flow chart.

A/C SWITCH ON (NX & SENTRA 1.6L)

A/C SWITCH OFF (NX & SENTRA 1.6L)

A/C SWITCH ON (NX & SENTRA 2.0L - A/T)

A/C SWITCH OFF (NX & SENTRA 2.0L - A/T)

A/C SWITCH ON (NX & SENTRA 2.0L - M/T)

A/C SWITCH OFF (NX & SENTRA 2.0L - M/T)

Note. For Flow chart symbol identification (Scheme 13)

Scheme 13

DIAGNOSTIC CHARTS

Note. Some code charts include procedures using Nissan's Consult Tester (J-38465). If consult tester is not available, disregard steps using consult tester and use alternate test procedure. The following abbreviations appear on charts: OK = Okay; NG = No Good.

Scheme 14

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Scheme 47

See also:
• DETONATION SENSOR LOCATION
• RELAYS