Diagnostic Procedure

WARNING: This page is about a different car, the 2002 Nissan Sentra. However, it is still accessible from the selected car via links, so may be relevant.

Start engine and let idle. Check for intake leaks. Stop engine and visually inspect exhaust system, 3-way catalyst and muffler for damage. If problem exist, repair as necessary and retest system. If problem does not exist, go to next step.
Check if EGR valve is stuck open. Perform DTC CONFIRMATION TEST under DTC P1402: EGR FUNCTION. If problem exists, repair EGR system as necessary and retest system. If problem does not exist, go to next step.
Start engine and let idle. Individually, disconnect fuel injector harness connectors. If engine speed momentarily drops, go to step 6 . If engine speed does not momentarily drop, listen to each fuel injector. If all injectors click, go to next step. If any injector does not click, repair injector or circuit and retest system. See SYSTEM & COMPONENT TESTING article.
Turn ignition off. Check for spark at misfiring cylinder(s). If spark is detected, go to next step. If no spark is detected, go to step 6 .
Check spark plug at misfiring cylinder(s). If spark plug is defective, replace spark plug and retest system. If spark plug is okay, go to next step.
Check compression. See BASIC DIAGNOSTIC PROCEDURES article. If compression is not within specification, repair engine as necessary and retest system. If compression is okay, go to next step.
Check fuel pressure. See BASIC DIAGNOSTIC PROCEDURES article. Fuel pressure should be 34 psi (2.4 kg/cm² ) with vacuum hose connected to fuel pressure regulator. Fuel pressure should be 43 psi (3.0 kg/cm² ) with vacuum hose disconnected from fuel pressure regulator. If fuel pressure is not as specified, repair fuel system as necessary. If fuel pressure is as specified, go to next step.
Check ignition timing. See BASIC DIAGNOSTIC PROCEDURES article. If ignition timing is incorrect, adjust as necessary and retest system. If ignition timing is okay, go to next step.

Check A/F sensor (sensor 1) input signal circuit. Disconnect PCM harness connector and A/F sensor harness connector. See Figure and Figure . For engine control components locations, see Figure -Figure . Check continuity between PCM harness connector and A/F sensor harness connector terminals. See PCM TO A/F SENSOR (SENSOR 1) CONNECTOR TERMINAL IDENTIFICATION table for terminal selections. Continuity should exist. Also, check for short to power and to ground on each wire. If problem does not exist, go to next step. If problem exists, repair circuit as necessary and recheck.

PCM TO A/F SENSOR (SENSOR 1) CONNECTOR TERMINAL IDENTIFICATION

ECM Terminal No.	Wire Color	A/F Sensor Terminal No.
62	White/Blue	2
63	White	5
64	Orange/Blue	1
65	Orange	6

Check A/F sensor (sensor 1) heater. See Figure . If A/F sensor (sensor 1) heater is OK, go to next step. If A/F sensor (sensor 1) heater is defective, replace A/F sensor (sensor 1).
Connect all disconnected components. Connect scan tool to Data Link Connector (DLC). Using scan tool, check MAF sensor signal. At idle, value should be 1.4-4.0 gm/sec. At 2500 RPM, value should be 5.4-10.0 gm/sec. If values are as specified, go to next step. If values are not as specified, repair MAF sensor or circuit. See DTC P0101, DTC P0102, DTC P0103 OR DTC P1102: MASS AIRFLOW (MAF) SENSOR .
Check for possible causes of rough idle. See ROUGH IDLE under SYMPTOMS in TROUBLE SHOOTING - NO CODES article. Repair as necessary and retest system. Clear any DTCs that may have been set by performing test. Problem may be intermittent. See TESTING PROCEDURE under SELF-DIAGNOSTIC SYSTEM.