Engine Controls - System/component Tests 2.4L: Other Nissan 240SX S14

Ground Circuits

1. Using an ohmmeter, check for continuity to ground on ECM terminals No. 10, 19, 39, 43, 50, 106, 112 and 118. (Scheme 67) Resistance should be zero ohms. If resistance is not zero ohms, repair open to ground.
2. Using a DVOM, touch negative lead of voltmeter to a good ground. Using positive lead of voltmeter, backprobe each ground terminal at ECM connector. With vehicle running, voltmeter should indicate less than one volt. If voltmeter reading is greater than one volt, check for open, corrosion or loose connection on ground lead.

Power Circuits

1. Turn ignition switch to ON position. Using a voltmeter, check for battery voltage between chassis ground and ECM terminals No. 38, 56 and 61. (Scheme 67) If battery voltage is not present, check fusible link and fuse "G".
2. Turn ignition switch to OFF position. Using a voltmeter, check for battery voltage between chassis ground and ECM power back-up terminals. If battery voltage is not present, check for overheated relays, fusible links and wiring.

Scheme 67

ENGINE SENSORS & SWITCHES

Note. For ECM connector terminal ID, see PIN VOLTAGE CHARTS article and the WIRING DIAGRAMS article.

CAMSHAFT POSITION SENSOR

1. Camshaft position sensor is located on engine front cover. Faults in camshaft position sensor circuit should set Diagnostic Trouble Code (DTC) PO340. To test system, see DTC P0340 - CAMSHAFT POSITION (CMP) SENSOR procedures in «TESTS W/CODES»(ref-17825) article.
2. To test camshaft position sensor, start and run engine at idle. Connect voltmeter to ground. Backprobe specified wire terminals of sensor connector. See CAMSHAFT POSITION SENSOR VOLTAGE TEST table.
3. Voltage pulse signal should be approximately 2.7 volts. If voltage is not as specified, check for damaged or dirty signal plate in camshaft position sensor, and for shorted or open harness. If harness and signal plate are okay, replace camshaft position sensor.

CAMSHAFT POSITION SENSOR VOLTAGE TEST

CRANKSHAFT POSITION SENSOR (CKP)

Faults in CKP sensor or circuit should set a Diagnostic Trouble Code (DTC) P0335 or P01336. For testing procedure, refer to DTC P0O335 OR P1336 - CRANKSHAFT POSITION (CKP) SENSOR in the TESTS W/CODES article.

Automatic Transmission

1. Disconnect throttle position sensor and closed throttle position switch harness connector.
2. While gradually releasing accelerator pedal, check engine speed at which continuity exists between switch terminals. See CLOSED THROTTLE POSITION SWITCH CONTINUITY table. If necessary, adjust switch continuity by rotating throttle position sensor body.

CLOSED THROTTLE POSITION SWITCH CONTINUITY

INHIBITOR SWITCH

1. Disconnect and inspect inhibitor switch 8-pin and 2-pin harness connectors for pushed-out, bent, damaged or corroded terminals. Repair connector(s) as necessary. Connectors are located on top or on side of transaxle/transmission.
2. Using INHIBITOR SWITCH CONTINUITY table, place shift lever in indicated position. Check continuity between terminals of inhibitor switch 8-pin and 2-pin connector listed in table. (Scheme 68) If switch does not function as indicated, replace switch.

INHIBITOR SWITCH CONTINUITY

Scheme 68

KNOCK SENSOR

Faults in knock sensor or circuit should set a Diagnostic Trouble Code (DTC) P0325. For testing procedure, refer to DTC P0325 - KNOCK SENSOR (KS) in the TESTS W/CODES article. To locate sensor, see KNOCK SENSOR LOCATION table.

KNOCK SENSOR LOCATION

ENGINE COOLANT TEMPERATURE (ECT) SENSOR

1. Faults in engine (coolant) temperature sensor circuit should set Diagnostic Trouble Code (DTC) P0115, or DTC P0125. To test system, see DTC P0115 OR P0125 - ENGINE COOLANT TEMPERATURE (ECT) SENSOR in the «TESTS W/CODES»(ref-17825) article.
2. To test sensor, disconnect sensor connector. See ENGINE COOLANT TEMPERATURE (ECT) SENSOR LOCATION table. Measure resistance across sensor connector terminals. See ENGINE COOLANT TEMPERATURE (ECT) SENSOR RESISTANCE table. If resistance is not as specified, replace sensor.

ENGINE COOLANT TEMPERATURE (ECT) SENSOR LOCATION

ENGINE (COOLANT) TEMPERATURE SENSOR RESISTANCE

EXHAUST GAS TEMPERATURE SENSOR

1. Faults in exhaust gas temperature sensor circuit should set DTC P1401. To test system, see DTC P1401 - EGR TEMPERATURE SENSOR diagnostic procedures in the «TESTS W/CODES»(ref-17825) article.
2. 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.

INTAKE AIR TEMPERATURE SENSOR

Faults in IAT sensor or circuit should set a Diagnostic Trouble Code (DTC) PO110. For testing procedure, refer to DTC P0110 - INTAKE AIR TEMPERATURE (IAT) SENSOR in the TESTS W/CODES article.

HEATED OXYGEN SENSOR (HO2S)

1. Faults in oxygen sensor circuit may set DTC P0130/P0135 (front) or DTC P0136/P0141 (rear). To test system, see procedures in the «TESTS W/CODES»(ref-17825) article.
2. To test front HO2S circuit, start and warm engine to operating temperature. Connect DVOM between ECM terminals No. 46 (White wire) and terminal No. 43 (Black wire).
3. Check voltage while engine speed is 2000 RPM under no load. Maximum voltage should be above 0.6 volt at least once. Minimum voltage should be below 0.35 volt at least once.
4. To test rear HO2S circuit, start and warm engine to operating temperature. Connect DVOM between ECM terminals No. 52 (White wire) and terminal No. 43 (Black wire).
5. To test HEATER element of rear HO2S, check resistance between outer 2 terminals of 3-wire connector. Resistance should be 5.2-8.2 ohms at 77°F (25°C). Also check continuity between sensor center terminal and both outer terminals. No continuity should exist between center terminal and outer terminals. If sensor does not test as specified, replace oxygen sensor.
6. Check voltage while increasing engine speed to 4000 RPM under no load at least 10 times (depress and release accelerator pedal). Voltage should be above 0.6 volt at least once. If voltage is as specified, system is functioning properly at this time.
7. If voltage is not as specified, check voltage while increasing engine speed to 6000 RPM under no load or keep engine at idle for 10 minutes, then check voltage. Voltage should be below 0.55 volt at least once.

MASS AIRFLOW SENSOR

1. Faults in mass airflow sensor circuit shoule set Diagnostic Trouble Code (DTC) P0100. For testing procedure, refer to DTC P0100 - MASS AIRFLOW (MAF) SENSOR in the «TESTS W/CODES»(ref-17825) article.
2. To test mass airflow sensor, warm engine to operating temperature. Pull rubber protector away from mass airflow sensor connector so terminals can be backprobed. At mass airflow sensor connector, measure voltage between ground and White wire.
3. If voltage is not as specified in MASS AIRFLOW SENSOR VOLTAGE TEST table, check for dust or foreign material in hot wire air passage of mass airflow sensor. If air passage is okay, replace mass airflow sensor.

MASS AIRFLOW SENSOR VOLTAGE TEST (1)

NEUTRAL POSITION SWITCH

Disconnect neutral position switch 2-pin harness connector located on top of transmission extension housing. Check continuity between neutral position switch 2-pin connector terminals. Continuity should exist with transmission in Neutral. Continuity should not exist in any other position. If neutral position switch does not function as described, replace switch.

POWER STEERING OIL PRESSURE SWITCH

Disconnect power steering oil pressure switch connector. Switch is attached to power steering high pressure hose. Start engine and check switch for continuity. Replace switch if continuity is not as specified in POWER STEERING OIL PRESSURE SWITCH table.

POWER STEERING OIL PRESSURE SWITCH

THROTTLE POSITION (TP) SENSOR

1. Faults in TP sensor circuit should set DTC P0120. To test system, see DTC P0120 - THROTTLE POSITION (TP) SENSOR diagnostic procedures in the «TESTS W/CODES»(ref-17825) article.
2. To test TP sensor, disconnect TP sensor connector. TP sensor is mounted on side of throttle body. While opening and closing throttle, check resistance across specified wire terminals of TP sensor connector. See THROTTLE POSITION SENSOR RESISTANCE TEST table.
3. If resistance is not as specified, check wiring harness. If no faults are found, adjust TP sensor. See «ADJUSTMENTS»(ref-17823) article. If resistance is still not as specified after adjustment, replace TP sensor.

THROTTLE POSITION SENSOR RESISTANCE TEST

VEHICLE SPEED SENSOR

1. Faults in vehicle speed sensor circuit should DTC P0500. To test system, see DTC P0500 - VEHICLE SPEED SENSOR (VSS) diagnostic procedures in the «TESTS W/CODES»(ref-17825) article.
2. To test sensor, remove vehicle speed sensor from transaxle/transmission. While rotating sensor shaft by hand, check AC voltage across sensor connector terminals. If about 0.5 volt AC is not present, 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

1. Electronic Control Module (ECM or ECCS) relay.
2. Fuel pump relay.
3. Main relay.
4. Radiator (cooling) fan relay.
5. Mixture heater relay.
6. Park/neutral (inhibitor) 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 internal circuits. See the 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 the WIRING DIAGRAMS article to identify proper relay terminals (wire colors) for testing. Energize relay and check continuity of relay output circuit.

EXAMPLE: Fuel Pump Relay (Maxima Shown)

1. Turn ignition on. Ensure battery voltage exists at Blue wire of fuel pump relay. (Scheme 69) If battery voltage is not present at Blue wire, check for a blown 10-amp power fuse or an open circuit between fuse and relay.
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.

Scheme 69

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: Safety Relay (Maxima Shown)

1. Turn ignition on. Using a voltmeter, check for battery voltage at Blue wire of safety relay. (Scheme 69) 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.

EGR Control Solenoid

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

EGR & Canister Control Solenoid

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

Fast Idle Control Device (FICD) Solenoid

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

FUEL DELIVERY

Note. For fuel system pressure testing, see FUEL PRESSURE under FUEL SYSTEM in the BASIC TESTING article. If ECM receives incorrect start (cranking) signal, fuel delivery system may not operate properly. See START SIGNAL under IGNITION SYSTEMS .

Fuel Pressure Regulator

Connect fuel pressure gauge. Disconnect vacuum hose from fuel pressure regulator. Plug hose end. Connect hand-held vacuum pump to fuel pressure regulator. Start engine. Gradually apply vacuum to fuel pressure regulator. Compare fuel pressure to regulated pressure in FUEL PRESSURE table in the BASIC TESTING article. If pressure is not as specified, replace fuel pressure regulator.

FUEL PUMP

To test fuel pump, disconnect fuel pump connector, accessible through trunk. At fuel pump connector, check resistance between fuel pump terminals specified in FUEL PUMP RESISTANCE TEST table. If resistance is not as specified, replace fuel pump.

FUEL PUMP RESISTANCE TEST

FUEL INJECTOR

Disconnect fuel injector harness connector. 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

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) VALVE

Disconnect AAC valve harness connector. Check resistance across AAC valve connector terminals. If resistance is not approximately 10 ohms, replace AAC valve. Ensure plunger does not stick and plunger spring is not broken.

Disconnect FICD solenoid harness connector. 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 SYSTEMS

Note. For basic ignition checks, see the BASIC TESTING article.

POWER TRANSISTOR

Note. The DVOM must have a diode check position and be able to measure up to 20 megohms to perform this test.

1. Disconnect power transistor connector. (Scheme 70) At power transistor connector, check continuity between the following terminals, noting ohmmeter test lead polarity: "a" (+) and "b" (-). "a" (+) and "c" (-). "b" (+) and "a" (-). "b" (+) and "c" (-). "c" (+) and "a" (-). "c" (+) and "b" (-).
2. If there is continuity, replace power transistor. If there is no continuity, reverse DVOM 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 70

Timing Advance

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

1. Camshaft or crankshaft position sensor.
2. Airflow meter.
3. Engine (coolant) temperature sensor.
4. Idle switch.
5. Start (cranking) signal.
6. Battery voltage.

Detonation (Knock) Retard

Faults in knock sensor (detonation retard) circuit may set Code 34 or DTC P0325. To test system, see CODE 34 or DTC P0325 diagnostic procedures in the TESTS W/CODES article. To test knock (detonation) sensor, see ENGINE SENSORS & SWITCHES.

Carbon Canister

Remove hoses from carbon canister. Blow air into canister ports as shown. (Scheme 71) 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 71

EGR Backpressure Transducer (EGR-BPT) & EGR Canister Backpressure Transducer (EGRC-BPT) Valves

Plug one port of EGR-BPT (EGRC-BPT) valve and apply vacuum to other port. (Scheme 72) 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 (EGRC-BPT) valve.

Scheme 72

1. Disconnect vacuum lines and electrical connector from solenoid. Remove solenoid. Using hand-held vacuum pump, apply vacuum to port "A" of solenoid. (Scheme 73) Vacuum should now be available at port "C", but not at port "B".
2. Apply battery voltage across solenoid connector terminals. Apply vacuum to port "A" of solenoid. Vacuum should now be available at port "B", but not at port "C". Replace solenoid if it does not operate as specified.

1. Faults in EGR and canister control solenoid circuit may set Code 105 or DTC P1400. To test circuit, see CODE 105 or DTC P1400 diagnostic procedures in the «TESTS W/CODES»(ref-17825) article.
2. To test solenoid, disconnect vacuum lines and electrical connector from solenoid. Remove solenoid. Using hand-held vacuum pump, apply vacuum to port "A" of solenoid. (Scheme 73) Vacuum should now be available at port "C", but not at port "B".
3. Apply battery voltage across solenoid connector terminals. Apply vacuum to port "A" of solenoid. Vacuum should now be available at port "B", but not at port "C". Replace solenoid if it does not operate as specified.

Scheme 73

EGR Function

Faults in EGR function circuit may set Code 32 or DTC P0400. To test function, see CODE 32 or DTC P0400 diagnostic procedures in the TESTS W/CODES article.

EGRC-BPT Valve Function

1. Faults in EGRC-BPT system may set Code 36 or DTC P0402. To test overall function of system, go to next step. To test EGRC-BPT valve, see EGR BACKPRESSURE TRANSDUCER (EGR-BPT) & EGR CANISTER BACKPRESSURE TRANSDUCER (EGRC-BPT) VALVES (above).
2. Disconnect vacuum hose to fuel pressure regulator (on intake manifold). Disconnect vacuum hose to EGR and canister control solenoid at EGRC-BPT valve. Connect fuel pressure regulator manifold vacuum hose to EGRC-BPT valve, to apply intake manifold vacuum directly to EGRC-BPT valve.
3. Start engine. Check for EGR valve lifting with engine speed less than 1500 RPM under no load. EGR valve should remain closed. Check for EGR valve lifting with engine speed at 2000-35000 RPM under no load. EGR valve should open, then close without sticking when engine is returned to idle.

EGR Valve

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

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

RADIATOR COOLING FANS

The ECM 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 A/C SWITCH ON or A/C SWITCH OFF table. If cooling fan does not operate as specified, see RADIATOR (COOLING) FAN CONTROL TEST.

A/C SWITCH ON (1)

A/C SWITCH OFF

REAR WINDOW DEFOGGER

1. Turn ignition off. Disconnect ECM harness connector. ECM is located on right kick panel. Turn ignition on.
2. Measure voltage between ground and ECM terminal No. 55 (Blue/Red wire). Battery voltage should exist. If voltage is as specified, go to next step. If voltage is not as specified, check rear window defogger relay, rear window defogger timer, smart entrance control unit (if equipped), harness, and connectors.
3. Disconnect and reconnect harness connectors in circuit. Check ECM terminals, harness, and connector terminals for damage, corrosion or improper connection. Repair or replace as necessary.

5TH POSITION SWITCH

1. Turn ignition off. Disconnect 5th position switch 2-pin harness connector located on side of transmission housing. Check continuity between ground and Black wire of 5th position switch 2-pin harness connector. Continuity should exist. If continuity exists, go to next step. If continuity does not exist, check harness and connectors between switch and ground.
2. Disconnect ECM harness connector. Check continuity between ECM terminal No. 7 (Yellow/Blue wire) and 5th position switch 2-pin harness connector Yellow/Blue wire. Continuity should exist. If continuity exists, go to next step. If continuity does not exist, check harness and connectors between ECM and switch.
3. With transmission in 5th gear, ensure continuity exists at 5th position switch connector. Replace switch if necessary. If switch is okay, disconnect and inspect ECM, harness, and connectors for pushed-out, bent, damaged or corroded terminals. Repair harness or connectors as necessary.