Nissan Frontier. Manual - part 385

ENGINE CONTROL SYSTEM

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DIAGNOSIS AND REPAIR WORK FLOW

BASIC INSPECTION

DIAGNOSIS AND REPAIR WORK FLOW

Trouble Diagnosis Introduction

INFOID:0000000009480754

INTRODUCTION

The engine has an ECM to control major systems such as fuel con-

trol, ignition control, idle air control system, etc. The ECM accepts

input signals from sensors and instantly drives actuators. It is essen-

tial that both input and output signals are proper and stable. At the

same time, it is important that there are no malfunctions such as vac-

uum leaks, fouled spark plugs, or other malfunctions with the engine.

It is much more difficult to diagnose an incident that occurs intermit-

tently rather than continuously. Most intermittent incidents are

caused by poor electric connections or improper wiring. In this case,

careful checking of suspected circuits may help prevent the replace-

ment of good parts.

A visual check only may not find the cause of the incidents. A road

test with CONSULT (or GST) or a circuit tester connected should be

performed. Follow the WORK FLOW on "WORK FLOW".

Before undertaking actual checks, take a few minutes to talk with a

customer who approaches with a driveability complaint. The cus-

tomer can supply good information about such incidents, especially

intermittent ones. Find out what symptoms are present and under

what conditions they occur. A DIAGNOSTIC WORKSHEET like the

example on "Worksheet Sample" should be used.

Start your diagnosis by looking for conventional malfunctions first.

This will help troubleshoot driveability malfunctions on an electroni-

cally controlled engine vehicle.

WORK FLOW

Overall Sequence

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DIAGNOSIS AND REPAIR WORK FLOW

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*1: Include 1st trip DTC.

*2: Include 1st trip freeze frame data.

Detailed Flow

1.

GET INFORMATION FOR SYMPTOM

1. Get the detailed information from the customer about the symptom (the condition and the environment

when the incident/malfunction occurred) using the "DIAGNOSTIC WORKSHEET".

2. Ask if the customer requests I/M examination.

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DIAGNOSIS AND REPAIR WORK FLOW

Malfunction information, obtained>>GO TO 2.

No malfunction information, but a request for I/M examination>>GO TO 13.

2.

CHECK DTC

1. Check DTC of “ALL DTC Reading”.

2. Perform the following procedure if DTC is displayed.

-

Record DTC and freeze frame data. (Print them out with CONSULT or GST.)

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Erase DTC. (Refer to 

EC-82, "DTC Index"

.)

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Study the relationship between the cause detected by DTC and the symptom described by the customer.

(Symptom Matrix Chart is useful. Refer to 

EC-461, "Symptom Matrix Chart"

.)

3. Check related service bulletins for information.
Are any symptoms described and any DTCs detected?

Symptom is described, DTC is displayed>>GO TO 3.

Symptom is described, DTC is not displayed>>GO TO 4.

Symptom is not described, DTC is displayed>>GO TO 5.

3.

CONFIRM THE SYMPTOM

Try to confirm the symptom described by the customer (except MIL ON).

Also study the normal operation and fail safe related to symptom. Refer to 

EC-465, "Fuel Cut Control (at No

Load and High Engine Speed)"

 and 

EC-80, "Fail-safe Chart"

.

Diagnosis Work Sheet is useful to verify the incident.

Verify relation between the symptom and the condition when the symptom is detected.

>> GO TO 5.

4.

CONFIRM THE SYMPTOM

Also study the normal operation and fail safe related to symptom. Refer to 

EC-465, "Fuel Cut Control (at No

Load and High Engine Speed)"

 and 

EC-80, "Fail-safe Chart"

.

Diagnosis Work Sheet is useful to verify the incident.

Verify relation between the symptom and the condition when the symptom is detected.

>> GO TO 6.

5.

PERFORM DTC CONFIRMATION PROCEDURE

Perform DTC Confirmation Procedure for the displayed DTC, and then make sure that DTC is detected again.

If two or more DTCs are detected, refer to 

EC-82, "DTC Inspection Priority Chart"

 and determine trouble diag-

nosis order.

NOTE:

• Freeze frame data is useful if the DTC is not detected.

• Perform Overall Function Check if DTC Confirmation Procedure is not included on Service Manual. This

simplified check procedure is an effective alternative though DTC cannot be detected during this check.

If the result of Overall Function Check is NG, it is the same as the detection of DTC by DTC Confirmation

Procedure.

Is DTC detected?

YES

>> GO TO 10.

NO

>> Check according to 

GI-42, "Intermittent Incident"

.

6.

PERFORM BASIC INSPECTION

Perform 

EC-117, "Basic Inspection"

.

With CONSULT>>GO TO 7.

Without CONSULT>>GO TO 9.

7.

PERFORM SPEC IN DATA MONITOR MODE

 With CONSULT

Make sure that “MAS A/F SE-B1”, “B/FUEL SCHDL”, and “A/F ALPHA-B1” are within the SP value using

“SPEC” of “DATA MONITOR” mode using CONSULT. Refer to 

EC-138, "Description"

.