Engine Controls - Basic Diagnostic Procedures - 4 Cyl & V6: Other Nissan Altima L31

RETRIEVE & RECORD CODES

Prior to conducting a physical mechanical inspection, retrieve and record any Diagnostic Trouble Codes (DTCs) that are currently set in Engine Control Module (ECM) memory. See SELF-DIAGNOSTIC SYSTEM in appropriate SELF-DIAGNOSTICS article. Record any DTCs that are present at this time. Review recovered DTCs, if set, or if battery is disconnected or other DTCs are set during mechanical inspection portion of basic diagnostic procedures.

Compression

Start engine and warm to normal operating temperature. Turn ignition off. Release fuel pressure. See FUEL PRESSURE RELEASE in FUEL SYSTEM. On Distributorless Ignition System (DIS) equipped models, remove all ignition coils. On all other models, disconnect distributor 2-pin harness connector (for ignition coil). On all models, remove all spark plugs. Depress accelerator pedal fully to hold throttle valve wide open. Attach compression tester to cylinder No. 1. Crank engine at specified speed and record highest gauge indication. See appropriate COMPRESSION SPECIFICATIONS table. Repeat measurement for each cylinder.

4-CYLINDER COMPRESSION SPECIFICATIONS

V6 COMPRESSION SPECIFICATIONS

Exhaust System Backpressure

Visually inspect exhaust system for dents, damage and leaks. Repair or replace as necessary. Exhaust system can be checked using a vacuum or pressure gauge.

If using a vacuum gauge, connect vacuum gauge hose to intake manifold vacuum port. Start engine. Observe vacuum gauge. Open throttle part way and hold steady. If vacuum gauge reading slowly drops after stabilizing, check exhaust system for a restriction.

If using a pressure gauge, remove front oxygen sensor. Connect a 0-5 psi pressure gauge. Run engine at 2500 RPM. If exhaust system backpressure is greater than 2 psi, exhaust system or catalytic converter is plugged. Repair or replace as necessary.

FUEL PRESSURE

Begin basic diagnosis of fuel system by determining fuel system pressure. If fuel pump is inoperative, check fuel pump fuse. If fuse is okay, see FUEL SYSTEM in SYSTEM & COMPONENT TESTING article. See WIRING DIAGRAMS article for specific circuit or wire color.

FUEL PRESSURE RELEASE

To relieve fuel system pressure, remove fuel pump fuse. Start engine, and allow it to run until it stalls. Crank engine 2 or 3 more times to verify all pressure has dissipated.

CHECKING FUEL PRESSURE

1. Turn ignition off. Connect fuel gauge between fuel filter outlet and fuel tube using a "T" connector. Install fuel pump fuse.
2. Start engine. Check fuel line connections for leaks. Check fuel pressure with engine idling. Disconnect vacuum hose from pressure regulator. Recheck fuel pressure.
3. Compare fuel pressure readings on pressure gauge with specifications. See «FUEL PRESSURE»(ref-135504-S29734747022002102300000) table. Release fuel system pressure as described in «FUEL PRESSURE RELEASE»(ref-135504-S01957061042002022200000) . Disconnect fuel pressure gauge. Reconnect fuel lines. Start engine and check for fuel leaks.

FUEL PRESSURE

IGNITION CHECKS

Note. I35 and Maxima uses distributorless ignition system.

Spark

To determine cause of no-spark condition, check for spark at coil wire and each spark plug wire using spark tester. DO NOT crank engine excessively. Inspect secondary coil wire for arcing while testing spark at plugs. Check electrical connections at Camshaft Position (CMP) sensor, ignition coil and power transistor.

Ignition Coil Power Source

1. Disconnect ignition coil 2-pin harness connector. Turn ignition on. Measure voltage at appropriate wire at ignition coil harness connector. See «IGNITION COIL POWER SOURCE TERMINAL IDENTIFICATION»(ref-135504-S18589306222002022200000) table.
2. If battery voltage is present, check ignition coil resistance. See «IGNITION COIL RESISTANCE»(ref-135504-S13722083682002022200000) . If battery voltage does not exist, check continuity of entire circuit between battery and ignition coil, including fusible link and ignition switch. See «WIRING DIAGRAMS»(ref-135817) article.

IGNITION COIL POWER SOURCE TERMINAL IDENTIFICATION

Power Transistor

See IGNITION CHECKS in SYSTEM & COMPONENT TESTING article.

Ignition Coil Resistance

1. Carefully inspect external housing for burned spots indicating secondary circuit arcing to primary or ground circuits. Disconnect ignition coil primary 2-pin harness connector. Measure resistance between primary connector terminals.
2. Measure resistance between secondary tower and positive terminal of coil primary connector. Positive terminal is identified by wire color. See «IGNITION COIL POWER SOURCE TERMINAL IDENTIFICATION»(ref-135504-S18589306222002022200000) table. If either resistance is not as specified, replace ignition coil. See appropriate IGNITION COIL RESISTANCE table.

IGNITION COIL RESISTANCE (EXCEPT SENTRA) - OHMS @ 68°F (20°C)

IGNITION COIL RESISTANCE (SENTRA) - OHMS @ 77°F (25°C)

Camshaft Position (CMP) Sensor

For CMP sensor testing, see appropriate SELF-DIAGNOSTICS article.

Crankshaft Position (CKP) Sensor

For CKP sensor testing, see appropriate SELF-DIAGNOSTICS article.

Ignition Coil Power Source & Ground

1. Disconnect 3-pin ignition coil harness connector. Turn ignition on. Measure voltage between ground and terminal No. 3 (Red wire on I35, Maxima, Pathfinder and QX4, Green/White wire on Sentra) at ignition coil harness connector.
2. If voltage is present, go to next step. If voltage is not present, check continuity of entire circuit between battery and ignition coil, including fusible link and ignition switch. See «WIRING DIAGRAMS»(ref-135817) article.
3. Turn ignition off. Check continuity between ground and ignition coil connector terminal No. 2 (Black wire). If continuity is not present, repair ground circuit between ignition coil connector and ground. Repeat test for remaining coils.

Ignition Coil/Power Transistor Resistance

Disconnect ignition coil/power transistor harness connector. Measure resistance between terminals No. 3 (Red wire on I35, Maxima, Pathfinder and QX4, Green/White wire on Sentra) and No. 2 (Black wire). If resistance is zero ohms, replace ignition coil/power transistor.

If a fault is present in CMP sensor, see appropriate SELF-DIAGNOSTICS article.

If a fault is present in CKP sensor, see in appropriate SELF DIAGNOSTICS article.

IDLE SPEED & IGNITION TIMING

Ensure idle speed and ignition timing are set to specification. Improper setting of ignition timing and idle speed may cause driveability problems and/or false setting of trouble codes. For adjustment procedures, see THROTTLE POSITION SWITCH, IGNITION TIMING & IDLE SPEED in ON-VEHICLE ADJUSTMENTS article.

IDLE SPEED (1)

IGNITION TIMING SPECIFICATIONS (1)

SUMMARY

If no faults were found while performing BASIC DIAGNOSTIC PROCEDURES, proceed to SELF-DIAGNOSTICS article. If no hard codes are found in self-diagnostics, proceed to TROUBLE SHOOTING - NO CODES article for diagnosis by symptom (i.e., ROUGH IDLE, NO START, etc.) or intermittent diagnostic procedures.