Infiniti M45 (Y34). Manual — part 346

TROUBLE DIAGNOSIS

EC-73

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EC

TROUBLE DIAGNOSIS

PFP:00004

Trouble Diagnosis Introduction

ABS002DL

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 incidents such as vacuum
leaks, fouled spark plugs, or other incidents 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-II (or GST) or a circuit tester connected should
be performed. Follow the Work Flow on

EC-74

.

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

EC-76

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.

MEF036D

SEF233G

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EC-74

TROUBLE DIAGNOSIS

WORK FLOW
Flow Chart

*1

If time data of “SELF-DIAG
RESULTS” is other than[0] or [1t],
perform

EC-132, "TROUBLE DIAG-

NOSIS FOR INTERMITTENT INCI-
DENT"

.

*2

If the incident cannot be verified, per-
form

EC-132, "TROUBLE DIAGNO-

SIS FOR INTERMITTENT
INCIDENT"

.

*3

If the on board diagnostic system
cannot be performed, check main
power supply and ground circuit.
Refer to

EC-133, "POWER SUPPLY

AND GROUND CIRCUIT"

.

*4

If malfunctioning part cannot be
detected, perform

EC-132, "TROU-

BLE DIAGNOSIS FOR INTERMIT-
TENT INCIDENT"

.

*5

EC-60, "Driving Pattern"

*6

EC-128, "TROUBLE DIAGNOSIS -
SPECIFICATION VALUE"

PBIB1043E

TROUBLE DIAGNOSIS

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EC

Description for Work Flow

STEP

DESCRIPTION

STEP I

Get detailed information about the conditions and the environment when the incident/symptom occurred using the

EC-76, "DIAGNOSTIC WORKSHEET"

.

STEP II

Before confirming the concern, check and write down (print out using CONSULT-II or GST) the (1st trip) DTC and the
(1st trip) freeze frame data, then erase the DTC and the data. (Refer to

EC-62, "HOW TO ERASE EMISSION-

RELATED DIAGNOSTIC INFORMATION"

.) The (1st trip) DTC and the (1st trip) freeze frame data can be used when

duplicating the incident at STEP III & IV.
If the incident cannot be verified, perform

EC-132, "TROUBLE DIAGNOSIS FOR INTERMITTENT INCIDENT"

.

Study the relationship between the cause, specified by (1st trip) DTC, and the symptom described by the customer.
(The Symptom Matrix Chart will be useful. See

EC-86, "Symptom Matrix Chart"

.)

Also check related service bulletins for information.

STEP III

Try to confirm the symptom and under what conditions the incident occurs.
The DIAGNOSTIC WORK SHEET and the freeze frame data are useful to verify the incident. Connect CONSULT-II
to the vehicle in DATA MONITOR (AUTO TRIG) mode and check real time diagnosis results.
If the incident cannot be verified, perform

EC-132, "TROUBLE DIAGNOSIS FOR INTERMITTENT INCIDENT"

.

If the malfunction code is detected, skip STEP IV and perform STEP V.

STEP IV

Try to detect the (1st trip) DTC by driving in (or performing) the DTC Confirmation Procedure. Check and read the (1st
trip) DTC and (1st trip) freeze frame data by using CONSULT-II or GST.
During the (1st trip) DTC verification, be sure to connect CONSULT-II to the vehicle in DATA MONITOR (AUTO TRIG)
mode and check real time diagnosis results.
If the incident cannot be verified, perform

EC-132, "TROUBLE DIAGNOSIS FOR INTERMITTENT INCIDENT"

.

In case the DTC Confirmation Procedure is not available, perform the Overall Function Check instead. The (1st trip)
DTC cannot be displayed by this check, however, this simplified check is an effective alternative.
The NG result of the Overall Function Check is the same as the (1st trip) DTC detection.

STEP V

Take the appropriate action based on the results of STEP I through IV.
If the malfunction code is indicated, proceed to TROUBLE DIAGNOSIS FOR DTC PXXXX.
If the normal code is indicated, proceed to the BASIC INSPECTION. (Refer to

EC-81, "Basic Inspection"

.) Then per-

form inspections according to the Symptom Matrix Chart. (Refer to

EC-86, "Symptom Matrix Chart"

.)

STEP VI

Identify where to begin diagnosis based on the relationship study between symptom and possible causes. Inspect the
system for mechanical binding, loose connectors or wiring damage using (tracing) Harness Layouts.
Gently shake the related connectors, components or wiring harness with CONSULT-II set in “DATA MONITOR
(AUTO TRIG)” mode.
Check the voltage of the related ECM terminals or monitor the output data from the related sensors with CONSULT-II.
Refer to

EC-98, "ECM Terminals and Reference Value"

,

EC-123, "CONSULT-II Reference Value in Data Monitor

Mode"

.

The Diagnostic Procedure in EC section contains a description based on open circuit inspection. A short circuit
inspection is also required for the circuit check in the Diagnostic Procedure. For details, refer to Circuit Inspection in

GI-26, "How to Perform Efficient Diagnosis for an Electrical Incident"

.

Repair or replace the malfunction parts.
If malfunctioning part cannot be detected, perform

EC-132, "TROUBLE DIAGNOSIS FOR INTERMITTENT INCI-

DENT"

.

STEP VII

Once you have repaired the circuit or replaced a component, you need to run the engine in the same conditions and
circumstances which resulted in the customer's initial complaint.
Perform the DTC Confirmation Procedure and confirm the normal code [DTC No. P0000] is detected. If the incident is
still detected in the final check, perform STEP VI by using a method different from the previous one.
Before returning the vehicle to the customer, be sure to erase the unnecessary (already fixed) (1st trip) DTC in ECM
and TCM (Transmission control module). (Refer to

EC-62, "HOW TO ERASE EMISSION-RELATED DIAGNOSTIC

INFORMATION"

and

AT-40, "HOW TO ERASE DTC"

.)

EC-76

TROUBLE DIAGNOSIS

DIAGNOSTIC WORKSHEET
Description

There are many operating conditions that lead to the malfunction of
engine components. A good grasp of such conditions can make trou-
bleshooting faster and more accurate.
In general, each customer feels differently about an incident. It is
important to fully understand the symptoms or conditions for a cus-
tomer complaint.
Utilize a diagnostic worksheet like the one on the next page in order
to organize all the information for troubleshooting.
Some conditions may cause the MIL to come on steady or blink and
DTC to be detected. Examples:

●

Vehicle ran out of fuel, which caused the engine to misfire.

●

Fuel filler cap was left off or incorrectly screwed on, allowing fuel
to evaporate into the atmosphere.

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