Engine Controls - Tests W/o Codes — Nissan Sentra B13 (1990-1994)

INTRODUCTION

Before diagnosing symptoms or intermittent faults, perform steps in BASIC TESTING and TESTS W/CODES articles. Use this article to diagnose driveability problems existing when a hard fault code is not present.

Note. Some driveability problems may have been corrected by manufacturer with a revised computer calibration chip or computer control unit. Check with manufacturer for latest chip or computer application.

Symptom checks can direct the technician to malfunctioning component(s) for further diagnosis. A symptom should lead to a specific component test, system test or adjustment.

Use intermittent test procedures to locate driveability problems that DO NOT occur when the vehicle is being tested. These test procedures should also be used if a soft (intermittent) trouble code was present, but no problem was found during self-diagnostic testing.

The recommended procedures for each symptom will be indicated by number(s) from one to 25, and may also contain specific instructions related to that number. See SYMPTOM PROCEDURE DEFINITION. Not all recommended procedures apply to all vehicles.

Note. For specific testing procedures, see I - SYS/COMP TESTS article. For specifications, see ADJUSTMENTS or SPECIFICATIONS article.

SYMPTOM DIAGNOSIS

Symptom checks cannot be used properly unless the problem occurs while vehicle is being tested. To reduce diagnostic time, ensure steps in BASIC TESTING and TESTS W/CODES articles were performed before diagnosing a symptom. Symptoms available for diagnosis include the following

Hard Start/Will Not Start
High Idle
Unstable Idling
Hesitation
Poor Driveability
Engine Stall
Backfire

Note. Recommended procedures for symptoms listed above are given in numbers from 1 to 28. See SYMPTOM PROCEDURE DEFINITION.

Cold

6, 1, 26 (4-cyl. Pathfinder/Pickup), 5, 2, 4, 7, 17, 19, 18.

Normal Conditions

6, 1, 2, 4, 7, 10, 17, 19, 18 (& 20 on V6 except Maxima with direct ignition system).

Hot

1, 15, 2, 4, 17, 19, 18.

Warm

5, 8, 9, 21.

After Warm-Up

10, 25, 2, 4, 7, 1, 28, 8, 3, 12, 17, 18.

Hunting

13, 25, 7, 8, 10.

7, 8, 22, 23.

Under Normal Conditions

7, 28, 14, 8.

15, 14 (& 8 on NX & Sentra).

Lack Of Power/Stumble

1, 8 (& 20 on V6 except Maxima with DIS).

Surge

28, 10, 18.

Detonation

8, 10, 11, 7.

26 (4-cyl. Pathfinder/Pickup), 5, 25, 2, 4, 7, 1, 17, 19, 18.

15, 25, 2, 4, 1, 17, 19, 18 (& 20 on V6 except Maxima with

direct ignition system).

On Momentary Acceleration

27, 25, 2, 4, 1, 17, 19, 18.

After Deceleration

27, 3, 25, 2, 4, 1, 28, 17, 19, 18.

Acceleration Or Cruising

25, 2, 4, 1, 8, 17, 19, 18.

Heavy Electrical Load

6, 25, 2, 4, 1, 17, 19, 18.

While Turning

Check fuel level, 25, 2, 4, 1, 17, 19, 18.

Intake

7, 8, 23.

Exhaust

24.

SYMPTOM PROCEDURE DEFINITION

The recommended procedures (specified numerically) are interpreted as follows. These steps help determine and rectify the cause of specific symptom.

Ensure fuel pressure is within specification.
Perform appropriate test in INJECTOR MALFUNCTION diagnostic chart in I - SYS/COMP TESTS article. Use DIAGNOSTIC CHARTS DIRECTORY table in I - SYS/COMP TESTS article to locate chart.
Inspect throttle body ports and valves for deposits, wear or plugging. Clean or replace as necessary.
Check for spark using spark tester.
Check idle speed control circuit. See IDLE CONTROL SYSTEM in I - SYS/COMP TESTS article.
Ensure battery and charging system are okay.
Check spark plug for improper gap or fouling.
Ensure there are no vacuum leaks in intake system.
Disconnect oxygen sensor connector(s). Run engine at 2000 RPM for 30 seconds. Return to idle. If idle RPM decreases, repair intake system air leak.
Check EGR control valve operation.
Check EGR control valve solenoid operation.
Ensure engine has adequate compression.
Disconnect exhaust gas sensor connector(s). If symptom is no longer present, check exhaust gas sensor operation. See TESTS W/CODES article.
Disconnect and plug canister purge line. If symptom is no longer present, check purge and vacuum lines.
Disconnect vacuum hose from fuel pressure regulator. If symptom is no longer present, check for vapor-locked fuel.
Disconnect exhaust gas sensor connector(s). Operate engine under no load at 1500-2000 RPM for 30 seconds. If RPM decreases, repair air leak in intake system.
Check ECU harness connector.
Try a known good ECU.
Check ECU power source and ground circuit. See ECU POWER SOURCE & GROUND diagnostic chart in I - SYS/COMP TESTS article. Use DIAGNOSTIC CHARTS DIRECTORY table in I - SYS/COMP TESTS article to locate chart.
Check timing belt for proper installation.
Check throttle linkage operation.
Try a known good airflow meter.
Check for intake valve deposits.
Check engine temperature sensor. See ENGINE (COOLANT) TEMPERATURE SENSOR in I - SYS/COMP TESTS article.
Perform power balance test.
Ensure fast idle cam holds throttle valve open.
With engine idling, disconnect TPS connector (Stanza) or AAC valve connector (all others). If engine RPM does not decrease, check AAC valve circuit. See IDLE CONTROL SYSTEM in I - SYS/COMP TESTS article.
Check exhaust gas sensor operation. See TESTS W/CODES article.

INTERMITTENT PROBLEM DIAGNOSIS

Intermittent fault testing requires duplicating circuit or component failure to identify the problem. These procedures may lead to the computer setting a fault code (on some systems) which may help in diagnosis.

If problem vehicle does not produce fault codes, monitor voltage or resistance values using a DVOM while attempting to reproduce conditions causing intermittent fault. A status change on DVOM indicates a fault has been located.

Use a DVOM to pinpoint faults. When monitoring voltage, ensure ignition is in ON position, or engine is running. Ensure ignition is in OFF position or negative battery cable is disconnected when monitoring circuit resistance. Status changes on DVOM during test procedures indicate area of fault.

TEST PROCEDURES (NX, SENTRA, STANZA, 240SX & 300ZX)

Two different diagnostic modes are available through the ECCS. Mode I is used as a bulb check and malfunction warning. Mode II is the self-diagnostic system and is used to obtain trouble codes for component or circuit failures. Mode II also monitors air/fuel mixture ratio by using the Red LED on ECU and CHECK ENGINE light.

Note. For additional information on self-diagnostic system, see TESTS W/CODES article.

Intermittent Simulation

To reproduce the conditions creating an intermittent fault, use the following methods

Lightly vibrate component.
Heat component.
Wiggle or bend wiring harness.
Spray component with water.
Remove/apply vacuum source.

Monitor circuit/component voltage or resistance while simulating intermittent. If engine is running, monitor for self-diagnostic codes. Use test results to identify a faulty component or circuit.

TEST PROCEDURES (MAXIMA, PATHFINDER & PICKUP)

Five different diagnostic modes are available through the ECCS. Diagnostic Mode I and Mode II monitor air/fuel mixture ratio using LED inspection lights. Mode III is the self-diagnostic system and is used to obtain trouble codes for component or circuit failures. Mode IV monitors for malfunction(s) in the system's on-off control switches. Mode V is the real-time diagnostic system; it monitors the system and its components during actual driving, and is particularly sensitive to intermittent symptoms.