Engine Controls - System & Component Testing: Other Infiniti QX4 I

Power & Ground Circuits (Altima & Sentra)

1. Start engine. If engine starts, go to step 6. If engine does not start, turn ignition off and on. Measure voltage between ground and PCM harness connector terminal No. 38 by backprobing. For PCM locations (Scheme 52)or (Scheme 53). For PCM terminal identification (Scheme 54) If battery voltage exists, go to next step. If battery voltage does not exist, repair open or short circuit. See appropriate diagram in WIRING DIAGRAMS article.
2. Turn ignition off. Disconnect PCM harness connector. Check continuity between ground and PCM harness connector terminals No. 10, 19, 39, 43, 106, 112 and 118. (Scheme 54) If continuity exists on all wires, go to next step. If continuity does not exist on any wire, repair open in appropriate wire. See appropriate diagram in WIRING DIAGRAMS article.
3. Disconnect ECCS relay, located near PCM. Measure voltage between ground and ECCS relay harness connector terminals No. 1 and 3 (White/Blue wires). (Scheme 55) If battery voltage exists, go to next step. If battery voltage does not exist, repair open or short circuit. See appropriate diagram in WIRING DIAGRAMS article.
4. Turn ignition off. Check continuity of White/Green wire between PCM harness connector terminal No. 4 and ECCS relay harness connector terminal No. 2. (Scheme 54)and (Scheme 55). If continuity exists, go to next step. If continuity does not exist, repair open in White/Green wire.
5. Reconnect all harness connectors. Check fuel injectors and circuits. See «FUEL CONTROL»(ref-91146-S16746955622001030200000) under FUEL SYSTEM. Repair as necessary. If no problems are found, go to next step.
6. Measure voltage between ground and PCM harness connector terminals No. 113 (except Sentra 1.6L) and No. 70 (all models) by backprobing. If battery voltage exists, go to next step. If battery voltage does not exist, repair open or short circuit. See appropriate diagram in WIRING DIAGRAMS article.
7. While turning ignition on then off, measure voltage between ground and PCM harness connector terminals No. 56 and 61 by backprobing. Battery voltage should exist for a few seconds after ignition is turned off. If voltage is as specified, go to step 13. If battery voltage does not exist, go to next step. If battery voltage exists for more than a few seconds after ignition is turned off, go to step 12.
8. Turn ignition off. Disconnect PCM harness connector. Disconnect ECCS relay located near PCM. Check continuity of White/Red wires between ECCS relay harness connector terminal No. 5 and PCM harness connector terminals No. 56 and 61. (Scheme 54)and (Scheme 55). If continuity exists on both wires, go to next step. If continuity does not exist on either wire, repair open in White/Red wire(s).
9. Measure voltage between ground and ECCS relay harness connector terminals No. 1 and 3 (White/Blue wires). (Scheme 55) If battery voltage exists, go to next step. If battery voltage does not exist, repair open or short circuit. See appropriate diagram in WIRING DIAGRAMS article.
10. Turn ignition off. Check continuity of White/Green wire between PCM harness connector terminal No. 4 and ECCS relay harness connector terminal No. 2. (Scheme 54)and (Scheme 55). If continuity exists, go to next step. If continuity does not exist, repair open in White/Green wire.
11. On Altima, check continuity of White/Blue wires between PCM harness connector terminal No. 113 and ECCS relay harness connector terminals No. 1 and 3. If continuity exists, go to next step. If continuity does not exist, repair open in White/Blue wire(s).
12. On all models, Check ECCS relay. See «RELAYS»(ref-91146-S19127946852001030200000) under RELAYS & SOLENOIDS. Replace, if necessary and retest system. If relay is okay, go to next step.
13. Turn ignition off. Disconnect PCM harness connector. Check continuity between ground and PCM harness connector terminals No. 10, 19, 39, 43, 106, 112 and 118. (Scheme 54) If continuity exists on all wires, go to next step. If continuity does not exist on any wire, repair open in appropriate wire.
14. No problem is indicated at this time. Problem may be intermittent. See TESTING PROCEDURE under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - INTRODUCTION article.

Scheme 52

Scheme 53

Scheme 54

Scheme 55

Power & Ground Circuits (Frontier)

1. Start engine. If engine starts, turn engine off and go to next step. If engine does not start, turn ignition off and on. Measure voltage between ground and PCM harness connector terminal No. 24 (White/Green wire on 4-cylinder models, or White/Blue wire on V6 models) by backprobing. (Scheme 56)and (Scheme 57). If battery voltage exists, go to step 8. If battery voltage does not exist, repair open or short circuit. See appropriate diagram in WIRING DIAGRAMS article.
2. Measure voltage between ground and PCM harness connector terminal No. 80 (Light Blue wire) by backprobing. (Scheme 57) If battery voltage exists, go to next step. If battery voltage does not exist, repair open or short circuit. See appropriate diagram in WIRING DIAGRAMS article.
3. While turning ignition on and off, measure voltage between ground and PCM harness connector terminals No. 67, 72 and 117 (Black/Pink wires) by backprobing. Battery voltage should exist for a few seconds after turning ignition off. If voltage is as specified, go to step 8. If battery voltage does not exist, go to next step. If battery voltage exists for more than a few seconds, go to step 7.
4. Disconnect PCM harness connector. Disconnect ECCS relay harness connector, located near PCM. Check continuity of Black/Pink wires between ECCS relay harness connector terminal No. 3 and PCM harness connector terminals No. 67, 72 and 117. (Scheme 55)and (Scheme 57). If continuity exists, go to next step. If continuity does not exist, repair open in Black/Pink wire(s).
5. Measure voltage between ground and ECCS relay harness connector terminals No. 2 and 5 (Light Blue wires). (Scheme 55) If battery voltage exists, go to next step. If battery voltage does not exist, repair open or short circuit. See appropriate diagram in WIRING DIAGRAMS article.
6. Check continuity between PCM harness connector terminal No. 4 and ECCS relay harness connector terminal No. 1 (Light Green/Red wire on 4-cylinder models, or Orange/Black wire on V6 models). (Scheme 55)and (Scheme 57). If continuity exists, go to next step. If continuity does not exist, repair open circuit.
7. Check ECCS relay. See «RELAYS»(ref-91146-S19127946852001030200000) under RELAYS & SOLENOIDS. Replace, if necessary and retest system. If relay is okay, go to next step.
8. Turn ignition off. Disconnect PCM harness connector. Check continuity between ground and PCM harness connector terminals No. 10, 19, 25, 32, 116 and 124. If continuity exists, go to next step. If continuity does not exist, repair open ground circuit(s).
9. No problem is indicated at this time. Problem may be intermittent. See TESTING PROCEDURE under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - INTRODUCTION article.

Scheme 56

Scheme 57

Power & Ground Circuits (Maxima)

1. Start engine. If engine starts, go to next step. If engine does not start, turn ignition off and on. Measure voltage between ground and PCM harness connector terminal No. 24 (Red wire) by backprobing. (Scheme 52)and (Scheme 57). If battery voltage exists, go to step 8. If battery voltage does not exist, repair open or short circuit. See appropriate diagram in WIRING DIAGRAMS article.
2. Turn ignition off. Measure voltage between ground and PCM harness connector terminal No. 80 (White wire) by backprobing. (Scheme 57) If battery voltage exists, go to next step. If battery voltage does not exist, repair open or short circuit. See appropriate diagram in WIRING DIAGRAMS article.
3. While turning ignition on and off, measure voltage between ground and PCM harness connector terminals No. 67 and 72 (Red wires) by backprobing. Battery voltage should exist for a few seconds after turning ignition off. If voltage is as specified, go to step 8. If battery voltage does not exist, go to next step. If battery voltage exists for more than a few seconds, go to step 7.
4. Disconnect PCM harness connector. Remove ECCS relay. (Scheme 58) Check continuity of Red wires between ECCS relay harness connector terminal No. 5 and PCM harness connector terminals No. 67 and 72. (Scheme 57)and (Scheme 59). If continuity exists, go to next step. If continuity does not exist, repair open in Red wire(s).
5. Measure voltage between ground and ECCS relay harness connector terminals No. 2 and 3 (White/Blue wires). If battery voltage exists, go to next step. If battery voltage does not exist, repair open or short circuit. See appropriate diagram in WIRING DIAGRAMS article.
6. Check continuity of White/Blue wire between ECCS relay harness connector terminal No. 1 and PCM harness connector terminal No. 4. (Scheme 57)and (Scheme 59). If continuity exists, go to next step. If continuity does not exist, repair open in White/Blue wire.
7. Check ECCS relay. See «RELAYS»(ref-91146-S19127946852001030200000) under RELAYS & SOLENOIDS. Replace, if necessary and retest system. If relay is okay, go to next step.
8. Turn ignition off. Loosen and retighten engine ground bolts, located on intake manifold near fuel injectors. Disconnect PCM harness connector. Check continuity between ground and PCM harness connector terminals No. 10, 19, 25, 32, 108, 116 and 124. If continuity exists, go to next step. If continuity does not exist, repair open ground circuit(s).
9. Check PCM harness connector terminals for damage or corrosion. Repair as necessary, reconnect all connectors and retest system.

Scheme 58

Scheme 59

Pathfinder & QX4

1. Start engine. If engine starts, go to step 5. If engine does not start, go to next step.
2. Turn engine off and leave ignition on. Measure voltage between PCM harness connector terminal No. 24 (Black/White wire) and ground by backprobing. (Scheme 57)and (Scheme 60). If battery voltage exists, go to next step. If battery voltage does not exist, repair open or short circuit. See appropriate diagram in WIRING DIAGRAMS article.
3. Turn ignition off. Disconnect PCM harness connector. Check continuity between ground and PCM harness connector terminals No. 10, 19, 25, 32, 116 and 124. (Scheme 57) If continuity exists on all wires, go to next step. If continuity does not exist on any wire, repair open ground circuit(s).
4. Turn ignition off. Check continuity of Blue/Black wire between PCM harness connector terminal No. 4 and ECCS relay harness connector terminal No. 2. (Scheme 57)and (Scheme 59). If continuity exists, go to step 12. If continuity does not exist, repair open in Blue/Black wire.
5. Turn ignition on. Measure voltage between ground and PCM harness connector terminal No. 80 (White/Red wire) by backprobing. (Scheme 57) If battery voltage exists, go to next step. If battery voltage does not exist, repair open or short circuit. See appropriate diagram in WIRING DIAGRAMS article.
6. Turn ignition off. While turning ignition on then off, measure voltage between ground and PCM harness connector terminals No. 67, 72 and 117 (Black/White wires) by backprobing. Battery voltage should exist for a few seconds after ignition is turned off. If voltage is as specified, go to step 11. If battery voltage does not exist, go to next step. If battery voltage exists for more than a few seconds after ignition is turned off, go to step 10.
7. Turn ignition off. Disconnect PCM harness connector. Disconnect ECCS relay. (Scheme 61) Check continuity of Black/White wires between ECCS relay harness connector terminal No. 6 and PCM harness connector terminals No. 67, 72 and 117. (Scheme 57)and (Scheme 59). If continuity exists on all wires, go to next step. If continuity does not exist on any wire, repair open in Black/White wire(s).
8. Measure voltage between ground and ECCS relay harness connector terminals No. 1 and 7 (White/Red wires). (Scheme 59) If battery voltage exists, go to next step. If battery voltage does not exist, repair open or short circuit. See appropriate diagram in WIRING DIAGRAMS article.
9. Turn ignition off. Check continuity of Blue/Black wire between PCM harness connector terminal No. 4 and ECCS relay harness connector terminal No. 2. (Scheme 57)and (Scheme 59). If continuity exists, go to next step. If continuity does not exist, repair open in Blue/Black wire.
10. Check ECCS relay. See «RELAYS»(ref-91146-S19127946852001030200000) under RELAYS & SOLENOIDS. Replace, if necessary and retest system. If relay is okay, go to next step.
11. Turn ignition off. Disconnect PCM harness connector. Check continuity between ground and PCM harness connector terminals No. 10, 19, 25, 32, 116 and 124. (Scheme 57) If continuity exists, go to next step. If continuity does not exist, repair open ground circuit(s).
12. Check PCM harness connector terminals for damage or corrosion. Repair as necessary, reconnect all connectors and retest system.

Scheme 60

Scheme 61

Power & Ground Circuits (Quest)

1. Start engine. If engine starts, turn engine off and go to next step. If engine does not start, turn ignition off and on. Measure voltage between ground and PCM harness connector terminal No. 24 (Blue/Yellow wire) by backprobing. (Scheme 57)and (Scheme 62). If battery voltage exists, go to step 8. If battery voltage does not exist, repair open or short circuit. See appropriate diagram in WIRING DIAGRAMS article.
2. Measure voltage between ground and PCM harness connector terminal No. 80 (Yellow wire) by backprobing. (Scheme 57) If battery voltage exists, go to next step. If battery voltage does not exist, repair open or short circuit. See appropriate diagram in WIRING DIAGRAMS article.
3. While turning ignition on and off, measure voltage between ground and PCM harness connector terminals No. 67, 72 and 117 (Black/White wires) by backprobing. Battery voltage should exist for a few seconds after turning ignition off. If voltage is as specified, go to step 8. If battery voltage does not exist, go to next step. If battery voltage exists for more than a few seconds, go to step 7.
4. Disconnect PCM relay harness connector. Measure voltage between ground and PCM relay harness connector terminals No. 2 and 3 (Red wires). (Scheme 55) If battery voltage exists, go to next step. If battery voltage does not exist, repair open or short circuit. See appropriate diagram in WIRING DIAGRAMS article.
5. Disconnect PCM harness connector. Check continuity of White/Green wire between PCM harness connector terminal No. 4 and PCM relay harness connector terminal No. 1. (Scheme 55)and (Scheme 57). If continuity exists, go to next step. If continuity does not exist, repair open in White/Green wire.
6. Check continuity of Black/White wires between PCM relay harness connector terminal No. 5 and PCM harness connector terminals No. 67, 72 and 117. (Scheme 55)and (Scheme 57). If continuity exists, go to next step. If continuity does not exist, repair open in Black/White wire(s).
7. Check PCM relay. See «RELAYS»(ref-91146-S19127946852001030200000) under RELAYS & SOLENOIDS. Replace, if necessary and retest system. If relay is okay, go to next step.
8. Turn ignition off. Disconnect PCM harness connector. Check continuity between ground and PCM harness connector terminals No. 10, 19, 25, 32, 116 and 124. If continuity exists, go to next step. If continuity does not exist, repair open ground circuit(s).
9. No problem is indicated at this time. Problem may be intermittent. See TESTING PROCEDURE under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - INTRODUCTION article.

Scheme 62

ENGINE SENSORS & SWITCHES

Note. Sensor resistance and/or voltage values (when available) can be found in SENSOR OPERATING RANGE CHARTS article.

Note. For system testing of sensors and switches, see appropriate SELF-DIAGNOSTICS article.

CRANKSHAFT POSITION (CKP) SENSOR

See DTC P0335: CRANKSHAFT POSITION (CKP) SENSOR in appropriate SELF-DIAGNOSTICS article.

CAMSHAFT POSITION (CMP) SENSOR

See DTC P0340: CAMSHAFT POSITION (CMP) SENSOR in appropriate SELF-DIAGNOSTICS article.

ENGINE COOLANT TEMPERATURE (ECT) SENSOR

DTC P0115 OR P0125: ENGINE COOLANT TEMPERATURE (ECT) SENSOR in appropriate SELF-DIAGNOSTICS article.

EGR TEMPERATURE SENSOR

See EMISSION SYSTEMS & SUB-SYSTEMS .

IGNITION SWITCH (START SIGNAL)

Measure voltage between ground and PCM harness connector terminal No. 20 by backprobing. (Scheme 54)or (Scheme 57). Turn ignition switch to START position. Battery voltage should exist. With ignition switch in any other position, about zero volts should exist. If voltage is not as specified, repair ignition switch or circuit.

INTAKE AIR TEMPERATURE (IAT) SENSOR

See DTC P0110: INTAKE AIR TEMPERATURE (IAT) SENSOR in appropriate SELF-DIAGNOSTICS article.

FRONT HEATED OXYGEN SENSOR (HO2S)

See appropriate DTC for FRONT HEATED OXYGEN SENSOR (HO2S) in appropriate SELF-DIAGNOSTICS article. See appropriate DIAGNOSTIC TROUBLE CODE (DTC) IDENTIFICATION table in SELF-DIAGNOSTICS - INTRODUCTION article.

REAR HEATED OXYGEN SENSOR (HO2S)

See appropriate DTC for REAR HEATED OXYGEN SENSOR (HO2S) in appropriate SELF-DIAGNOSTICS article. See appropriate DIAGNOSTIC TROUBLE CODE (DTC) IDENTIFICATION table in SELF-DIAGNOSTICS - INTRODUCTION article.

KNOCK SENSOR (KS)

See DTC P0325: KNOCK SENSOR (KS) in appropriate SELF-DIAGNOSTICS article.

MASS AIRFLOW (MAF) SENSOR

See DTC P0100: MASS AIRFLOW (MAF) SENSOR in appropriate SELF-DIAGNOSTICS article.

POWER STEERING PRESSURE SWITCH

Turn ignition off. Disconnect power steering pressure switch harness connector located on high-pressure hose. Start engine. Check continuity between switch terminals. If switch has only one terminal, check continuity between ground and switch terminal. Continuity should exist when steering wheel is being turned. Continuity should not exist when steering wheel is not being turned. Replace switch, if continuity is not as specified.

Altima & Sentra

1. Start engine. Measure voltage between ground and PCM harness connector terminal No. 25 by backprobing. (Scheme 54) When steering wheel is turned quickly, voltage should be about zero volts. When steering wheel is not being turned, voltage should be about 5 volts. If voltage is as specified, system is okay. If voltage is not as specified, go to next step.
2. Turn ignition off. On Sentra 2.0L, disconnect power steering pressure switch harness connector located on high-pressure hose. Check continuity between ground and power steering pressure switch harness connector Black wire. If continuity exists, go to next step. If continuity does not exist, repair open in Black wire.
3. On all models, disconnect PCM harness connector. Check continuity between power steering pressure switch harness connector and PCM harness connector terminal No. 25 (Light Blue wire on Sentra, or Light Green/Black wire on Altima). If continuity exists, go to next step. If continuity does not exist, repair open circuit.
4. Check power steering pressure switch. See «POWER STEERING PRESSURE SWITCH»(ref-91146-S05249100902001030200000). Replace, if necessary. If power steering pressure switch is okay, go to next step.
5. No problem is indicated at this time. Problem may be intermittent. See TESTING PROCEDURE under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - INTRODUCTION article.

Frontier, Pathfinder, Quest & QX4

1. Start engine. Measure voltage between ground and PCM harness connector terminal No. 39 by backprobing. (Scheme 57) With steering wheel fully turned, voltage should be about zero volts. When steering wheel is not being turned, voltage should be about 5 volts. If voltage is as specified, system is okay. If voltage is not as specified, go to next step.
2. Turn ignition off. On Frontier V6, Pathfinder & QX4, turn ignition off. Disconnect power steering pressure switch harness connector located on high-pressure hose. Check continuity between ground and power steering pressure switch harness connector (Black wire on Pathfinder & QX4, or Black/Red wire on Frontier V6). If continuity exists, go to next step. If continuity does not exist, repair open ground circuit.
3. On all models, disconnect PCM harness connector. Check continuity between power steering pressure switch harness connector (Gray/Red wire on Frontier, Red/Black wire on Pathfinder & QX4, or Pink wire on Quest) and PCM harness connector terminal No. 39. If continuity exists, go to next step. If continuity does not exist, repair open circuit.
4. Check power steering pressure switch. See «POWER STEERING PRESSURE SWITCH»(ref-91146-S05249100902001030200000). Replace, if necessary. If power steering pressure switch is okay, go to next step.
5. No problem is indicated at this time. Problem may be intermittent. See TESTING PROCEDURE under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - INTRODUCTION article.

Maxima

1. Start engine. Measure voltage between ground and PCM harness connector terminal No. 39 by backprobing. (Scheme 57) Voltage should be about zero volts when steering wheel is being turned. Battery voltage should exist when steering wheel is not being turned. If voltage is as specified, system is okay. If voltage is not as specified, go to next step.
2. Turn ignition off. Disconnect Idle Air Control Valve-Fast Idle Control Device (IACV-FICD) harness connector. (Scheme 63) Turn ignition on. Measure voltage between ground and IACV-FICD harness connector terminal No. 1 (Red/Yellow wire). If battery voltage exists, go to next step. If battery voltage does not exist, repair open or short circuit. See appropriate diagram in WIRING DIAGRAMS article.
3. Turn ignition off. Disconnect power steering pressure switch harness connector, located on high-pressure hose. Check continuity of Green wire between IACV-FICD harness connector and power steering pressure switch harness connector. If continuity exists, go to next step. If continuity does not exist, repair open in Green wire.
4. Check continuity between ground and power steering pressure switch harness connector Black wire. If continuity exists, go to next step. If continuity does not exist, repair open in Black wire.
5. Disconnect PCM harness connector. Check continuity of Green wire between power steering pressure switch harness connector and PCM harness connector terminal No. 39. If continuity exists, go to next step. If continuity does not exist, repair open in Green wire.
6. Check power steering pressure switch. See «POWER STEERING PRESSURE SWITCH»(ref-91146-S05249100902001030200000). Check IACV-FICD. See «RELAYS & SOLENOIDS»(ref-91146-S19129435162001030200000). Replace components, if necessary. If components are okay, go to next step.
7. No problem is indicated at this time. Problem may be intermittent. See TESTING PROCEDURE under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - INTRODUCTION article.

Scheme 63

TANK FUEL TEMPERATURE SENSOR

See DTC P0180: TANK FUEL TEMPERATURE SENSOR in appropriate SELF-DIAGNOSTICS article.

THROTTLE POSITION (TP) SENSOR

See DTC P0120: THROTTLE POSITION (TP) SENSOR in appropriate SELF-DIAGNOSTICS article.

VEHICLE SPEED SENSOR (VSS)

See DTC P0500: VEHICLE SPEED SENSOR (VSS) in appropriate SELF-DIAGNOSTICS article.

A/C Clutch Relay

See MISCELLANEOUS CONTROLS .

ECCS, ECM & Fuel Pump Relays

1. Two types of relays are used: 4-terminal and 6-terminal. For relay location, see «ECCS, PCM & FUEL PUMP RELAY LOCATIONS»(ref-91146-S03588336542001030200000) table. Remove appropriate relay. Apply battery voltage and ground to terminals No. 1 and 2. (Scheme 64)or (Scheme 65).
2. Continuity should exist between terminals No. 3 and 5. On 6-terminal relays, continuity should also exist between terminals No. 6 and 7. On all relays, when battery voltage is removed, continuity should not exist. Replace relay, if test values are not as specified.

ECCS, PCM & FUEL PUMP RELAY LOCATIONS

Scheme 64

Scheme 65

SOLENOIDS

Note. For EGR and EVAP system components, see EMISSION SYSTEMS & SUB-SYSTEMS .

Relieving Fuel Pressure

Remove fuel pump fuse. Start engine and allow engine to run until it stalls. Crank engine an additional 2-3 times to ensure all pressure has dissipated.

Fuel Pressure

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

Fuel Pressure Regulator (Except Maxima)

1. Relieve fuel pressure from system. See «RELIEVING FUEL PRESSURE»(ref-91146-S35454238972001030200000) . Connect fuel pressure gauge in line between fuel filter and fuel rail. Remove vacuum hose from fuel pressure regulator, and plug hose. Connect hand-held vacuum pump to pressure regulator. Start engine and let idle.
2. Gradually apply vacuum to regulator. Fuel pressure should decrease as vacuum increases. Compare values to FUEL PRESSURE table in BASIC DIAGNOSTIC PROCEDURES article. If results are not as specified, replace fuel pressure regulator.

Fuel Pump

Disconnect fuel pump harness connector. For location, see FUEL PUMP HARNESS CONNECTOR LOCATIONS table. On Frontier 4-cylinder, measure resistance between fuel pump connector terminals P1 and P2. (Scheme 66) On Quest, measure resistance between fuel pump connector terminals No. 2 and 3. (Scheme 67) On all models except Frontier 4-cylinder and Quest, measure resistance between fuel pump 2-pin connector terminals. On all models, resistance should be 0.2-5.0 ohms at 77°F (25°C). Replace fuel pump if resistance is not as specified.

FUEL PUMP HARNESS CONNECTOR LOCATIONS

Scheme 66

Scheme 67

Fuel Pump Control System

1. On Quest, check inertia fuel shutoff switch located behind left kick panel. If switch has been triggered, push reset button. If switch has not been triggered, go to next step.
2. On all models, turn ignition on. Pinch fuel hose with fingers. Pulsation should be felt on fuel hose for 5 seconds after ignition is turned on (one second on Maxima). If pulsation is felt, system is okay. If pulsation is not felt, go to next step.
3. Turn ignition off. Disconnect fuel pump relay harness connector. For location, see «ECCS, PCM & FUEL PUMP RELAY LOCATIONS»(ref-91146-S03588336542001030200000) table under RELAYS & SOLENOIDS. Turn ignition on. Measure voltage between ground and fuel pump relay harness connector power supply terminals. See «FUEL PUMP RELAY CIRCUIT IDENTIFICATION»(ref-91146-S01394388822001030200000) table. If battery voltage exists, go to next step. If battery voltage does not exist, repair open or short circuit. See appropriate diagram in WIRING DIAGRAMS article.
4. Turn ignition off. Disconnect fuel pump harness connector. For location, see «FUEL PUMP HARNESS CONNECTOR LOCATIONS»(ref-91146-S38331638142001030200000) table under FUEL PUMP. Check continuity of fuel pump ground circuit. See «FUEL PUMP CIRCUIT IDENTIFICATION»(ref-91146-S26205710602001030200000) table. If continuity exists, go to next step. If continuity does not exist, repair open ground circuit.
5. Check continuity of fuel pump power supply wires between fuel pump harness connector and fuel pump relay harness connector. See «FUEL PUMP RELAY CIRCUIT IDENTIFICATION»(ref-91146-S01394388822001030200000) and «FUEL PUMP CIRCUIT IDENTIFICATION»(ref-91146-S26205710602001030200000) tables. If continuity exists, go to next step. If continuity does not exist, repair open in appropriate wire.
6. Disconnect PCM harness connector. (Scheme 52), (Scheme 53), (Scheme 56), (Scheme 60) or (Scheme 62). Check continuity of specified wire between fuel pump relay harness connector and PCM harness connector terminal No. 8 (on Altima and Sentra), No. 11 (on Frontier, Pathfinder, Quest and QX4) or No. 117 (on Maxima). See «FUEL PUMP RELAY CIRCUIT IDENTIFICATION»(ref-91146-S01394388822001030200000) table. (Scheme 54)or (Scheme 57). If continuity exists, go to next step. If continuity does not exist, repair open in appropriate wire.
7. Check fuel pump relay. See «RELAYS & SOLENOIDS»(ref-91146-S19129435162001030200000). Replace, if necessary. If fuel pump relay is okay, check fuel pump. See «FUEL PUMP»(ref-91146-S19127946852001030200000). Replace, if necessary. If fuel pump is okay, go to next step.
8. No problem is indicated at this time. Problem may be intermittent. See TESTING PROCEDURE under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - INTRODUCTION article.

FUEL PUMP RELAY CIRCUIT IDENTIFICATION

FUEL PUMP CIRCUIT IDENTIFICATION

Fuel Pump Control Module (Sentra 2.0L)

See DTC P1220: FUEL PUMP CONTROL MODULE (FPCM) in SELF-DIAGNOSTICS - SENTRA article.

Fuel Pump Relay

See RELAYS under RELAYS & SOLENOIDS.

Fuel Injector

Turn ignition off. Disconnect fuel injector harness connector. Measure resistance between injector terminals. Resistance should be 10-14 ohms at 77°F (25°C). Replace injector if resistance is not as specified.

Fuel Injector Circuits (Altima, Sentra & Frontier 4-Cylinder)

1. Start engine. Listen to each fuel injector. If every injector clicks, system is okay. If any injector does not click, go to next step.
2. Turn ignition off. Disconnect inoperative injector harness connector. Turn ignition on. Measure voltage between ground and injector harness connector Black/Red wire (White wire on Sentra 2.0L). If battery voltage exists, go to next step. If battery voltage does not exist, repair open or short circuit. See appropriate diagram in WIRING DIAGRAMS article.
3. Turn ignition off. Disconnect PCM harness connector. (Scheme 52), (Scheme 53) or (Scheme 56). Check continuity of specified wire between PCM harness connector and appropriate injector harness connector. See appropriate FUEL INJECTOR CIRCUIT IDENTIFICATION table. If continuity exists, go to next step. If continuity does not exist, repair open in appropriate wire.
4. Check fuel injector. See «FUEL INJECTOR»(ref-91146-S18313749482001030200000). Replace, if necessary. If injector is okay, no problem is indicated at this time. Problem may be intermittent. See TESTING PROCEDURE under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - INTRODUCTION article.

FUEL INJECTOR CIRCUIT IDENTIFICATION (ALTIMA & SENTRA)

FUEL INJECTOR CIRCUIT IDENTIFICATION (FRONTIER 4-CYLINDER

Fuel Injector Circuits (Frontier V6 & Quest)

1. Start engine. If engine does not start, go to next step. If engine starts, listen to each injector. If every injector clicks, system is okay. If any injector does not click, go to next step.
2. Turn ignition off. Disconnect inoperative injector harness connector. Turn ignition on. Measure voltage between ground and appropriate injector harness connector Black/Red wire (on Frontier V6), or Yellow wire (on Quest). If battery voltage exists, go to next step. If battery voltage does not exist, repair open or short circuit. See appropriate diagram in WIRING DIAGRAMS article.
3. Turn ignition off. Disconnect PCM harness connector. (Scheme 56)or (Scheme 62). Check continuity of specified wire between PCM harness connector and appropriate injector harness connector. See «FUEL INJECTOR CIRCUIT IDENTIFICATION (FRONTIER V6)»(ref-91146-S27381941702001030200000) or «FUEL INJECTOR CIRCUIT IDENTIFICATION (QUEST)»(ref-91146-S00064881472001030200000) table. If continuity exists, go to next step. If continuity does not exist, repair open in appropriate wire.
4. Check fuel injector. See «FUEL INJECTOR»(ref-91146-S18313749482001030200000). Replace, if necessary. If injector is okay, no problem is indicated at this time. Problem may be intermittent. See TESTING PROCEDURE under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - INTRODUCTION article.

FUEL INJECTOR CIRCUIT IDENTIFICATION (FRONTIER V6)

FUEL INJECTOR CIRCUIT IDENTIFICATION (QUEST)

Fuel Injector Circuits (Maxima)

1. Start engine. With engine idling, listen to each fuel injector. If every injector clicks, system is okay. If any injector does not click, go to next step.
2. Turn ignition off. For injectors on left bank, disconnect inoperative injector harness connector. Turn ignition on. Measure voltage between ground and injector harness connector Red wire. For injectors on right bank, disconnect injector sub-harness connector. (Scheme 68) Turn ignition on. Measure voltage between ground and injector sub-harness connector terminal No. 5 (Red wire). (Scheme 69) If battery voltage exists, go to next step. If battery voltage does not exist, repair open or short circuit. See appropriate diagram in WIRING DIAGRAMS article.
3. Turn ignition off. Disconnect PCM harness connector. (Scheme 52) Check continuity of specified wire between PCM harness connector and appropriate injector harness connector (on left bank), or sub-harness connector (on right bank). See «FUEL INJECTOR CIRCUIT IDENTIFICATION (MAXIMA)»(ref-91146-S29492709372001030200000) table. If continuity exists, go to next step. If continuity does not exist, repair open circuit.
4. If inoperative injector is on left bank, go to next step. If inoperative injector is on right bank, check continuity of appropriate wire between injector sub-harness connector and PCM harness connector. See «FUEL INJECTOR CIRCUIT IDENTIFICATION (MAXIMA)»(ref-91146-S29492709372001030200000) table. If continuity exists, go to next step. If continuity does not exist, repair open circuit.
5. Check fuel injector. See «FUEL INJECTOR»(ref-91146-S18313749482001030200000). Replace, if necessary. If injector is okay, no problem is indicated at this time. Problem may be intermittent. See TESTING PROCEDURE under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - INTRODUCTION article.

FUEL INJECTOR CIRCUIT IDENTIFICATION (MAXIMA)

Scheme 68

Scheme 69

Fuel Injector Circuits (Pathfinder & QX4)

1. Start engine. If engine does not start, go to step 5. If engine starts, listen to each injector. If every injector clicks, system is okay. If any injector does not click, go to next step.
2. Turn ignition off. Disconnect inoperative injector harness connector. Turn ignition on. Measure voltage between ground and injector harness connector White/Red wire. If battery voltage exists, go to next step. If battery voltage does not exist, repair open or short circuit. See appropriate diagram in WIRING DIAGRAMS article.
3. Turn ignition off. Disconnect PCM harness connector. (Scheme 52) Check continuity of specified wire between PCM harness connector and appropriate injector harness connector. See «FUEL INJECTOR CIRCUIT IDENTIFICATION (PATHFINDER & QX4)»(ref-91146-S14670555642001030200000) table. (Scheme 57) If continuity exists, go to next step. If continuity does not exist, repair open in appropriate wire.
4. Check fuel injector. See «FUEL INJECTOR»(ref-91146-S18313749482001030200000). Replace, if necessary. If injector is okay, no problem is indicated at this time. Problem may be intermittent. See TESTING PROCEDURE under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - INTRODUCTION article.
5. Turn ignition off. Disconnect Black 8-pin injector sub-harness connector located near oil filler cap. Turn ignition on. Measure voltage between ground and injector sub-harness connector terminal No. 1 (White/Red wire). (Scheme 69) If battery voltage exists, reconnect injector sub-harness connector and go to step 2. If battery voltage does not exist, go to next step.
6. Turn ignition off. Remover ECCS relay from underhood relay box. Measure voltage between ground and ECCS relay harness connector terminals No. 1 (White/Red wire) and No. 5 (Red/White wire). (Scheme 59) If battery voltage exists, go to next step. If battery voltage does not exist, repair open or short circuit. See appropriate diagram in WIRING DIAGRAMS article.
7. Check continuity of White/Red wire between ECCS relay harness connector terminal No. 3 and injector sub-harness connector terminal No. 1. (Scheme 59)and (Scheme 69). If continuity exists, go to next step. If continuity does not exist, repair open in White/Red wire.
8. Disconnect PCM harness connector. (Scheme 52) Check continuity of Blue/Black wire between ECCS relay harness connector terminal No. 2 and PCM harness connector terminal No. 4. (Scheme 57) If continuity exists, go to next step. If continuity does not exist, repair open in Blue/Black wire.
9. Check ECCS relay. See «RELAYS & SOLENOIDS»(ref-91146-S19129435162001030200000). Replace, if necessary. If ECCS relay is okay, check PCM power supply. See «POWERTRAIN CONTROL MODULE (PCM)»(ref-91146-S24961173562001030200000) under COMPUTERIZED ENGINE CONTROLS.

FUEL INJECTOR CIRCUIT IDENTIFICATION (PATHFINDER & QX4)

IDLE AIR CONTROL (IAC) VALVE

See DTC P0505: IDLE AIR CONTROL (IAC) in appropriate SELF-DIAGNOSTICS article.

IDLE AIR CONTROL VALVE (IACV)-AIR REGULATOR - SENTRA 2.0L

1. Turn ignition on. Pinch fuel hose with fingers. For 5 seconds after ignition is turned on, pulsation should be felt on fuel hose. If pulsation is felt, go to next step. If pulsation is not felt, check fuel pump control circuit. See «FUEL SYSTEM»(ref-91146-S13179891302001030200000) .
2. Turn ignition off. Disconnect IACV-air regulator harness connector. See «COMPONENT LOCATIONS»(ref-91146-S15997366042001030200000) . Turn ignition on. Measure voltage between ground and IACV-air regulator harness connector Black/Yellow wire. Battery voltage should exist for 5 seconds after ignition is turned on. If voltage is as specified, go to next step. If voltage is not as specified, repair open or short circuit. See appropriate diagram in WIRING DIAGRAMS article.
3. Turn ignition off. Check continuity between ground and IACV-air regulator harness connector Black wire. If continuity exists, go to next step. If continuity does not exist, repair open in Black wire.
4. Check IACV-air regulator for clogging. Clean as necessary. Measure resistance between IACV-air regulator terminals. Resistance should be 70-80 ohms at 77°F (25°C). Replace IACV-air regulator, if resistance is not as specified. If resistance is as specified, test is complete.

All Models Except Sentra 1.6L

Remove IACV-FICD solenoid. See COMPONENT LOCATIONS. Using jumper wires, apply battery voltage to IACV-FICD solenoid terminals. On Quest (Scheme 70) On all models, IACV-FICD solenoid should click. Inspect IACV-FICD solenoid plunger for sticking. Also check for broken spring. Replace IACV-FICD solenoid, if operation is not as specified.

Scheme 70

Sentra 1.6L

Remove IACV-FICD solenoid. See COMPONENT LOCATIONS. Measure resistance between IACV-FICD solenoid terminals No. 1 and 5. (Scheme 71) With IACV-FICD solenoid between 14°F (-10°C) and 122°F (50°C), resistance should be 162-278 ohms. With IACV-FICD solenoid between 122°F (50°C) and 212°F (100°C), resistance should be 205-327 ohms. Replace IACV-FICD, if resistance is not as specified.

Scheme 71

IGNITION SYSTEM

Faults in ignition signal should set a DTC P1320. For testing procedure, go to DTC P1320: IGNITION SIGNAL in appropriate SELF-DIAGNOSTICS article.

Ignition Coil

See IGNITION CHECKS in BASIC DIAGNOSTIC PROCEDURES article.

Power Transistor

Faults in power transistor should set a DTC P1320. For testing procedure, go to DTC P1320: IGNITION SIGNAL in appropriate SELF-DIAGNOSTICS article.

Crankshaft Position Sensor

PCM depends upon crankshaft position sensor for RPM signals. PCM uses signals to determine triggering of power transistors and fuel injectors. See DTC P0335 OR P1336: CRANKSHAFT POSITION (CKP) SENSOR in appropriate SELF-DIAGNOSTICS article.

See DTC P0340: CAMSHAFT POSITION (CMP) SENSOR in appropriate SELF-DIAGNOSTICS article.

Timing Advance System

PCM controls ignition timing advance based upon sensor input signals that reflect ignition timing needs. If timing problems are experienced, inspect input signals listed below for proper operation. To check input signals, see ENGINE SENSORS & SWITCHES or PCM pin voltage charts in PIN VOLTAGE CHARTS article.

1. A/C Clutch Signal
2. Closed Throttle Position Switch
3. Crankshaft Position Sensor
4. Engine Coolant Temperature
5. Ignition (START) Signal
6. Mass Airflow Sensor
7. Park/Neutral Switch
8. Power Steering Pressure Switch
9. Throttle Position Sensor
10. Vehicle Speed Sensor

EXHAUST GAS RECIRCULATION (EGR)

PCM controls EGR system based on engine operating conditions. On Maxima, PCM controls ground circuits for EGR Volume Control Valve (EGR-VCV). On all models except Maxima, PCM controls ground circuit for EGR Control (EGRC) solenoid. (Scheme 72)and (Scheme 73). EGR-VCV or EGRC solenoid remains closed under certain conditions including the following

1. Engine stopped.
2. Engine starting.
3. Engine idling.
4. Low engine coolant temperature.
5. Excessively high engine coolant temperature.
6. High engine speed.
7. Mass airflow sensor malfunction.

Scheme 72

Scheme 73

EGR System Check

See DTC P0400: EGR FUNCTION or DTC P1402: EGR FUNCTION in appropriate SELF-DIAGNOSTICS article.

EGR Backpressure Transducer (Except Maxima)

See DTC P0402: EGR BACKPRESSURE TRANSDUCER (EGR-BPT) in appropriate SELF-DIAGNOSTICS article.

EGRC Solenoid (Except Maxima)

See DTC 1400: EGR CONTROL (EGRC) SOLENOID in appropriate SELF-DIAGNOSTICS article.

See DTC P1401: EGR TEMPERATURE SENSOR in appropriate SELF-DIAGNOSTICS article.

EGR Valve (Except Maxima)

See DTC P0400: EGR FUNCTION or DTC P1402: EGR FUNCTION in appropriate SELF-DIAGNOSTICS article.

EGR Volume Control Valve (Maxima)

See DTC P0403: EGR VOLUME CONTROL VALVE (EGR-VCV) in SELF-DIAGNOSTICS - MAXIMA article.

EVAP Canister

Remove EVAP canister. Plug vent hose and blow air into port "A". Air should flow freely out of port "B". (Scheme 74) Replace EVAP canister, if operation is not as specified.

Scheme 74

On Board Refueling Vapor Recovery (Altima, Maxima & Sentra)

1. Remove EVAP canister with EVAP Canister Vent Control Valve (EVAP-CVCV) attached. Attempt to drain water from EVAP canister. If water does not drain from EVAP canister, go to next step. If water drains from EVAP canister, weigh EVAP canister with EVAP-CVCV attached. If EVAP canister weighs less than 4.0 lbs. (1.8 kg), go to next step. If EVAP canister weighs more than 4.0 lbs. (1.8 kg), replace EVAP canister and check hoses to water separator for poor connections or blockage. Inspect water separator for cracks or blockage. Clean or replace, if necessary.
2. If problem being diagnosed is a strong fuel odor from fuel filler while refueling, or refueling is difficult, go to step 6. If problem being diagnosed is a strong fuel odor from EVAP canister, go to next step.
3. Remove and drain fuel tank. Remove fuel gauge sending unit. On Altima, connect a hand vacuum pump to refueling EVAP vapor cut valve. (Scheme 75) On Maxima and Sentra, Connect a hand vacuum pump using a vacuum "T" to hoses "A" and "B". (Scheme 76) On all models, set fuel tank upside down. Apply 3.94 in. Hg of vacuum to vacuum "T". If vacuum holds, reinstall components and go to next step. If vacuum does not hold, refueling EVAP vapor cut valve is stuck open. Replace fuel tank.
4. On Altima, remove Refueling Control Valve (RCV). See VACUUM DIAGRAMS article. Inspect RCV for cracks. Blow air into port "A". Air should flow freely out of port "B". See. Blow air into port "C". Air should not flow. Apply 2.9 psi (.02 kg/cm 2 ) of pressure to ports "A" and "C". Vacuum should now hold. If operation is not as specified, replace RCV. If operation is as specified, test is complete.
5. On Maxima and Sentra, remove fuel filler cap. Blow air into hose "B". (Scheme 78) Air should flow freely into fuel tank. Blow air into hose "A". Air should not flow. Using a hand pressure pump using a vacuum "T", apply 2.9 psi (.02 kg/cm 2 ) of pressure to hoses "A" and "B". Air should not leak. If operation is as specified, test is complete. If operation is not as specified, replace fuel tank.
6. Check hoses between EVAP canister and refueling control valve for blockage, leak or misrouting. See VACUUM DIAGRAMS article. Repair as necessary. If hoses are okay, check signal line and recirculation line (on filler neck) for blockage or leak. Repair as necessary. If signal line and recirculation line are okay, go to next step.
7. On Altima, remove Refueling Control Valve (RCV). Inspect RCV for cracks. Blow air into port "A". Air should flow freely out of port "B". (Scheme 77) Blow air into port "C". Air should not flow. Apply 2.9 psi (.02 kg/cm 2 ) of pressure to ports "A" and "C". Vacuum should hold. If operation is not as specified, replace RCV. If operation is as specified, go to step 9.
8. On Maxima and Sentra, remove fuel filler cap. Blow air into hose "B". (Scheme 78) Air should flow freely into fuel tank. Blow air into hose "A". Air should not flow. Using a hand pressure pump using a vacuum "T", apply 2.9 psi (.02 kg/cm 2 ) of pressure to hoses "A" and "B". Air should not leak. If operation is as specified, go to next step. If operation is not as specified, replace fuel tank.
9. Remove and drain fuel tank. Remove fuel gauge sending unit. On Altima, blow air into refueling EVAP vapor cut valve. (Scheme 75) On Maxima and Sentra, blow air into hose "B" (to refueling EVAP vapor cut valve). (Scheme 76) On all models, air should flow freely into fuel tank. If air flows as specified, go to next step. If air does not flow as specified, refueling vapor cut valve is stuck closed. Replace fuel tank.
10. Check fuel filler tube and hose for blockage or leak. Repair or replace as necessary. If fuel filler tube is okay, remove fuel filler tube and hose. Insert a suitable rod into fuel tank. One-way fuel valve should open. When rod is removed, one-way fuel valve should close. If operation is not as specified, replace fuel tank. If operation is as specified, test is complete.

Scheme 75

Scheme 76

Scheme 77

Scheme 78

POSITIVE CRANKCASE VENTILATION (PCV)

With engine idling, remove vent hose from PCV valve. A hissing noise should be heard. Strong vacuum should be felt immediately when a finger is placed over valve inlet. Clean or replace PCV valve, if it does not operate as specified.

MISCELLANEOUS CONTROLS

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

1. A/C clutch relay is controlled by PCM. Under normal conditions, PCM will engage clutch relay by providing a ground circuit for relay windings. If PCM receives a wide open throttle signal from throttle position sensor while it is also receiving an A/C on signal from A/C auto amplifier, PCM will disengage relay.
2. Remove A/C relay located in underhood relay box. Apply battery voltage to terminals No. 1 and 2. (Scheme 64) Continuity should exist between terminals No. 3 and 5. When battery voltage is removed, continuity should not exist. Replace relay if continuity is not as specified.

Altima

1. Turn ignition off. Disconnect PCM harness connector. (Scheme 52) Turn ignition on. Measure voltage between ground and PCM harness connector terminal No. 55 (Blue/Red wire). (Scheme 54) With rear window defogger on, battery voltage should exist. With rear window defogger off, zero volts should exist. If voltage is as specified, go to next step. If voltage is not as specified, go to step 4.
2. Measure voltage between ground and PCM harness connector terminal No. 60 (Brown wire). With headlights or daytime running lights on, battery voltage should exist. With headlights and daytime running lights off, zero volts should exist. If voltage is as specified, go to next step. If voltage is not as specified, go to step 6.
3. Turn ignition off. Check continuity between ground and PCM harness connector terminal No. 59 (Light Green/Red wire). With blower fan turned on, continuity should exist. With blower fan turned off, continuity should not exist. If continuity is not as specified, go to step 8. If continuity is as specified, go to step 10.
4. Turn ignition off. Disconnect rear window defogger relay, located above passenger compartment fuse block. Check continuity of Blue/Red wire between PCM harness connector terminal No. 55 and rear window defogger relay harness connector terminal No. 5. If continuity exists, go to next step. If continuity does not exist, repair open in Blue/Red wire.
5. Disconnect rear window defogger timer and smart entrance control unit harness connectors, located behind center of instrument panel. Check continuity of Green/Red wire between rear window defogger relay harness connector terminal No. 2, rear window defogger timer harness connector terminal No. 2 and smart entrance control unit harness connector terminal No. 36. If continuity does not exist, repair open in Green/Red wire. If continuity exists, check rear window defogger system. See REAR WINDOW DEFOGGERS article in ACCESSORIES & EQUIPMENT. Repair as necessary.
6. Turn ignition off. Disconnect Light Blue 6-pin diode harness connector located behind left kick panel. Check continuity of Brown wire between PCM harness connector terminal No. 60 and diode harness connector terminal No. 4. If continuity exists, go to next step. If continuity does not exist, repair open in Brown wire.
7. Check continuity of Red/Yellow wire between diode harness connector terminal No. 6 and combination switch harness connector terminal No. 10. Also check continuity of Red/Black wire between diode harness connector terminal No. 1 and combination switch harness connector terminal No. 9. If continuity does not exist, repair open circuit. If continuity exists, check diode. Replace, if necessary. If diode is okay, test is complete.
8. Check continuity of Light Green/Red wire between PCM harness connector terminal No. 59, blower fan switch harness connector terminal No. 5 and push control unit harness connector terminal No. 19. If continuity exists, go to next step. If continuity does not exist, repair open in Light Green/Red wire.
9. Check continuity of Black wire between ground and blower fan switch harness connector terminal No. 6. If continuity does not exist, repair open in Black wire. If continuity exists, test is complete.
10. No problem is indicated at this time. Problem may be intermittent. See TESTING PROCEDURE under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - INTRODUCTION article.

1. Turn ignition off. Disconnect PCM harness connector. (Scheme 52) Turn ignition on. Measure voltage between ground and PCM harness connector terminal No. 79 (Red/White wire). (Scheme 57) With rear window defogger on, battery voltage should exist. With rear window defogger off, zero volts should exist. If voltage is not as specified, go to next step. If voltage is as specified, system is functioning properly.
2. Check rear window defogger for correct operation. See REAR WINDOW DEFOGGERS article in ACCESSORIES & EQUIPMENT. If rear window defogger operates normally, go to next step. If rear window defogger does not operate normally, repair as necessary.
3. Disconnect rear window defogger relay, located in underhood relay box. Check continuity between PCM terminal No. 79 (Red/White wire) and rear window defogger relay harness connector terminals No. 5 (Blue/Red wire) and No. 7 (Blue/Yellow wire). If continuity does not exist, repair open circuit. If continuity exists, test is complete.

1. Turn ignition off. Disconnect PCM harness connector. (Scheme 53) Turn ignition on. Measure voltage between ground and PCM harness connector terminal No. 55 (Blue/Red wire). (Scheme 54) With rear window defogger on, battery voltage should exist. With rear window defogger off, zero volts should exist. If voltage is as specified, go to next step. If voltage is not as specified, go to step 4.
2. Measure voltage between ground and PCM harness connector terminal No. 60 (Red/Blue wire). With headlights or daytime running lights on, battery voltage should exist. With headlights and daytime running lights off, zero volts should exist. If voltage is as specified, go to next step. If voltage is not as specified, go to step 6.
3. Turn ignition off. Check continuity between ground and PCM harness connector terminal No. 24 (Light Green/Black wire). With blower fan turned on, continuity should exist. With blower fan turned off, continuity should not exist. If continuity is not as specified, go to step 7. If continuity is as specified, go to step 9.
4. Turn ignition off. Disconnect rear window defogger relay, located below passenger compartment fuse block. Check continuity of Blue/Red wire between PCM harness connector terminal No. 55 and rear window defogger relay harness connector terminal No. 5. If continuity exists, go to next step. If continuity does not exist, repair open in Blue/Red wire.
5. Disconnect rear window defogger timer and smart entrance control unit harness connectors located under left side of instrument panel. Check continuity of Green/Red wire between rear window defogger relay harness connector terminal No. 2, rear window defogger timer harness connector terminal No. 2 and smart entrance control unit harness connector terminal No. 36. If continuity does not exist, repair open in Green/Red wire. If continuity exists, check rear window defogger system. See REAR WINDOW DEFOGGERS article in ACCESSORIES & EQUIPMENT. Repair as necessary.
6. Turn ignition off. Disconnect headlight switch harness connector. Check continuity of Red/Blue wire between headlight switch harness connector terminal No. 12 and PCM harness connector terminal No. 60. If continuity does not exist, repair open in Red/Blue wire. If continuity exists, test is complete.
7. Check continuity of Light Green/Red wire between PCM harness connector terminal No. 24, blower fan switch harness connector terminal No. 5 and push control unit harness connector terminal No. 19. If continuity exists, go to next step. If continuity does not exist, repair open in Light Green/Red wire.
8. Check continuity of Black wire between ground and blower fan switch harness connector terminal No. 6. If continuity does not exist, repair open in Black wire. If continuity exists, test is complete.
9. No problem is indicated at this time. Problem may be intermittent. See TESTING PROCEDURE under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - INTRODUCTION article.

FRONT ENGINE MOUNT CONTROL - MAXIMA

1. Start engine and warm to normal operating temperature. Set parking brake and let engine idle. While depressing brake pedal, shift transmission into Drive. Observe amount of body vibration. Increase engine speed to more than 1000 RPM. Disconnect front engine mount harness connector. (Scheme 79)
2. Allow engine to idle. Observe amount of body vibration. If amount of body vibration does not increase to more than amount observed in step 1), go to next step. If amount of body vibration increased to more than amount observed in step 1), system is okay. Test is complete.
3. Turn ignition off. Measure voltage between ground and front engine mount harness connector White wire. If battery voltage exists, go to next step. If battery voltage does not exist, repair open or short circuit. See appropriate diagram in WIRING DIAGRAMS article.
4. Disconnect PCM harness connector. (Scheme 52) Check continuity of White/Red wire between front engine mount harness connector and PCM harness connector terminal No. 34. (Scheme 57) Also check continuity of White/Blue wire between front engine mount harness connector and PCM harness connector terminal No. 33. If continuity exists, go to next step. If continuity does not exist, repair open circuit.
5. No problem is indicated at this time. Problem may be intermittent. See TESTING PROCEDURE under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - INTRODUCTION article. Visually inspect front engine mount. Replace, if damaged.

Scheme 79