Infiniti QX4 (R50). Manual - part 148

Introduction

NBEC0029

The ECM has an on board diagnostic system, which detects malfunctions related to engine sensors or actua-
tors. The ECM also records various emission-related diagnostic information including:

Emission-related diagnostic information

SAE Mode

Diagnostic Trouble Code (DTC)

Mode 3 of SAE J1979

Freeze Frame data

Mode 2 of SAE J1979

System Readiness Test (SRT) code

Mode 1 of SAE J1979

1st Trip Diagnostic Trouble Code (1st Trip DTC)

Mode 7 of SAE J1979

1st Trip Freeze Frame data

Test values and Test limits

Mode 6 of SAE J1979

The above information can be checked using procedures listed in the table below.

X: Applicable

—: Not applicable

DTC

1st trip DTC

Freeze Frame

data

1st trip Freeze

Frame data

SRT code

Test value

CONSULT-II

—

GST

X*1

—

*1: 1st trip DTCs for self-diagnoses concerning SRT items cannot be shown on the GST display.

The malfunction indicator lamp (MIL) on the instrument panel lights up when the same malfunction is detected
in two consecutive trips (Two trip detection logic), or when the ECM enters fail-safe mode. (Refer to EC-117.)

Two Trip Detection Logic

NBEC0030

When a malfunction is detected for the first time, 1st trip DTC and 1st trip Freeze Frame data are stored in
the ECM memory. The MIL will not light up at this stage. <1st trip>
If the same malfunction is detected again during the next drive, the DTC and Freeze Frame data are stored
in the ECM memory, and the MIL lights up. The MIL lights up at the same time when the DTC is stored. <2nd
trip> The “trip” in the “Two Trip Detection Logic” means a driving mode in which self-diagnosis is performed
during vehicle operation. Specific on board diagnostic items will cause the ECM to light up or blink the MIL,
and store DTC and Freeze Frame data, even in the 1st trip, as shown below.

X: Applicable

—: Not Exit

Items

MIL

DTC

1st trip DTC

1st trip

2nd trip

1st trip

displaying

2nd trip

displaying

1st trip

displaying

2nd trip

displaying

Blinking

Lighting

Blinking

Lighting

Misfire (Possible three way cata-
lyst damage) — DTC: P0300 -
P0306 (0701, 0605 — 0608) is
being detected

—

Misfire (Possible three way cata-
lyst damage) — DTC: P0300 -
P0306 (0701, 0605 — 0608) is
being detected

—

Closed loop control
— DTC: P1148 (0307), P1168
(0308)

—

Fail-safe items (Refer to EC-117.)

—

X*1

—

X*1

—

Except above

—

*1: Except “ECM”

IDX

ON BOARD DIAGNOSTIC SYSTEM DESCRIPTION

Introduction

EC-59

Emission-related Diagnostic Information

NBEC0031

DTC AND 1ST TRIP DTC

NBEC0031S01

The 1st trip DTC (whose number is the same as the DTC number) is displayed for the latest self-diagnostic
result obtained. If the ECM memory was cleared previously, and the 1st trip DTC did not reoccur, the 1st trip
DTC will not be displayed.
If a malfunction is detected during the 1st trip, the 1st trip DTC is stored in the ECM memory. The MIL will not
light up (two trip detection logic). If the same malfunction is not detected in the 2nd trip (meeting the required
driving pattern), the 1st trip DTC is cleared from the ECM memory. If the same malfunction is detected in the
2nd trip, both the 1st trip DTC and DTC are stored in the ECM memory and the MIL lights up. In other words,
the DTC is stored in the ECM memory and the MIL lights up when the same malfunction occurs in two con-
secutive trips. If a 1st trip DTC is stored and a non-diagnostic operation is performed between the 1st and
2nd trips, only the 1st trip DTC will continue to be stored. For malfunctions that blink or light up the MIL dur-
ing the 1st trip, the DTC and 1st trip DTC are stored in the ECM memory.
Procedures for clearing the DTC and the 1st trip DTC from the ECM memory are described in “HOW TO
ERASE EMISSION-RELATED DIAGNOSTIC INFORMATION”, EC-72.
For malfunctions in which 1st trip DTCs are displayed, refer to EC-69. These items are required by legal
regulations to continuously monitor the system/component. In addition, the items monitored non-continuously
are also displayed on CONSULT-II.
1st trip DTC is specified in Mode 7 of SAE J1979. 1st trip DTC detection occurs without lighting up the MIL
and therefore does not warn the driver of a problem. However, 1st trip DTC detection will not prevent the
vehicle from being tested, for example during Inspection/Maintenance (I/M) tests.
When a 1st trip DTC is detected, check, print out or write down and erase (1st trip) DTC and Freeze Frame
data as specified in “Work Flow” procedure Step II, refer to EC-99. Then perform “DTC Confirmation Proce-
dure” or “Overall Function Check” to try to duplicate the problem. If the malfunction is duplicated, the item
requires repair.

How to Read DTC and 1st Trip DTC

NBEC0031S0101

DTC and 1st trip DTC can be read by the following methods.

With CONSULT-II
With GST

CONSULT-II or GST (Generic Scan Tool) Examples: P0340, P1320, P0705, P0750, etc.
These DTCs are prescribed by SAE J2012.
(CONSULT-II also displays the malfunctioning component or system.)

1st trip DTC No. is the same as DTC No.

Output of a DTC indicates a malfunction. However, GST does not indicate whether the malfunction
is still occurring or has occurred in the past and has returned to normal. CONSULT-II can identify
malfunction status as shown below. Therefore, using CONSULT-II (if available) is recommended.

A sample of CONSULT-II display for DTC and 1st trip DTC is shown below. DTC or 1st trip DTC of a malfunc-
tion is displayed in SELF-DIAGNOSTIC RESULTS mode of CONSULT-II. Time data indicates how many times
the vehicle was driven after the last detection of a DTC.
If the DTC is being detected currently, the time data will be “0”.
If a 1st trip DTC is stored in the ECM, the time data will be “[1t]”.

SEF992X

FREEZE FRAME DATA AND 1ST TRIP FREEZE FRAME DATA

NBEC0031S02

The ECM records the driving conditions such as fuel system status, calculated load value, engine coolant
temperature, short term fuel trim, long term fuel trim, engine speed, vehicle speed and absolute pressure at
the moment a malfunction is detected.
Data which are stored in the ECM memory, along with the 1st trip DTC, are called 1st trip freeze frame data.

ON BOARD DIAGNOSTIC SYSTEM DESCRIPTION

Emission-related Diagnostic Information

EC-60

The data, stored together with the DTC data, are called freeze frame data and displayed on CONSULT-II or
GST. The 1st trip freeze frame data can only be displayed on the CONSULT-II screen, not on the GST. For
details, see EC-85.
Only one set of freeze frame data (either 1st trip freeze frame data or freeze frame data) can be stored in the
ECM. 1st trip freeze frame data is stored in the ECM memory along with the 1st trip DTC. There is no prior-
ity for 1st trip freeze frame data and it is updated each time a different 1st trip DTC is detected. However, once
freeze frame data (2nd trip detection/MIL on) is stored in the ECM memory, 1st trip freeze frame data is no
longer stored. Remember, only one set of freeze frame data can be stored in the ECM. The ECM has the fol-
lowing priorities to update the data.

Priority

Items

Freeze frame data

Misfire — DTC: P0300 - P0306
Fuel Injection System Function — DTC: P0171, P0172, P0174, P0175

Except the above items (Includes A/T related items)

1st trip freeze frame data

For example, the EGR malfunction (Priority: 2) was detected and the freeze frame data was stored in the 2nd
trip. After that when the misfire (Priority: 1) is detected in another trip, the freeze frame data will be updated
from the EGR malfunction to the misfire. The 1st trip freeze frame data is updated each time a different mal-
function is detected. There is no priority for 1st trip freeze frame data. However, once freeze frame data is
stored in the ECM memory, 1st trip freeze data is no longer stored (because only one freeze frame data or
1st trip freeze frame data can be stored in the ECM). If freeze frame data is stored in the ECM memory and
freeze frame data with the same priority occurs later, the first (original) freeze frame data remains unchanged
in the ECM memory.
Both 1st trip freeze frame data and freeze frame data (along with the DTCs) are cleared when the ECM
memory is erased. Procedures for clearing the ECM memory are described in “HOW TO ERASE EMISSION-
RELATED DIAGNOSTIC INFORMATION”, EC-72.

SYSTEM READINESS TEST (SRT) CODE

NBEC0031S03

System Readiness Test (SRT) code is specified in Mode 1 of SAE J1979.
As part of an enhanced emissions test for Inspection & Maintenance (I/M), certain states require the status of
SRT be used to indicate whether the ECM has completed self-diagnosis of major emission systems and com-
ponents. Completion must be verified in order for the emissions inspection to proceed.
If a vehicle is rejected for a State emissions inspection due to one or more SRT items indicating “INCMP”,
use the information in this Service Manual to set the SRT to “CMPLT”.
In most cases the ECM will automatically complete its self-diagnosis cycle during normal usage, and the SRT
status will indicate “CMPLT” for each application system. Once set as “CMPLT”, the SRT status remains
“CMPLT” until the self-diagnosis memory is erased.
Occasionally, certain portions of the self-diagnostic test may not be completed as a result of the customer’s
normal driving pattern; the SRT will indicate “INCMP” for these items.
NOTE:
The SRT will also indicate “INCMP” if the self-diagnosis memory is erased for any reason or if the ECM
memory power supply is interrupted for several hours.
If, during the state emissions inspection, the SRT indicates “CMPLT” for all test items, the inspector will con-
tinue with the emissions test. However, if the SRT indicates “INCMP” for one or more of the SRT items the
vehicle is returned to the customer untested.
NOTE:
If MIL is “ON” during the state emissions inspection, the vehicle is also returned to the customer untested even
though the SRT indicates “CMPLT” for all test items. Therefore, it is important to check SRT (“CMPLT”) and
DTC (No DTCs) before the inspection.

IDX

ON BOARD DIAGNOSTIC SYSTEM DESCRIPTION

Emission-related Diagnostic Information (Cont’d)

EC-61

SRT Item

=NBEC0031S0310

The table below shows required self-diagnostic items to set the SRT to “CMPLT”.

SRT item

(CONSULT-II indica-

tion)

Perfor-

mance Pri-

ority*

Required self-diagnostic items to set the SRT to “CMPLT”

Corresponding

DTC No.

CATALYST

Three way catalyst function

P0420, P0430

EVAP SYSTEM

EVAP control system (small leak) (negative pressure)

P0440

EVAP control system (very small leak) (negative pressure)/
(positive pressure)

P1441

EVAP control system purge flow monitoring

P1447

O2 SENSOR

Heated oxygen sensor 1 (front) (circuit)

P0130, P0150

Heated oxygen sensor 1 (front) (lean shift monitoring)

P0131, P0151

Heated oxygen sensor 1 (front) (rich shift monitoring)

P0132, P0152

Heated oxygen sensor 1 (front) (response monitoring)

P0133, P0153

Heated oxygen sensor 1 (front) (high voltage)

P0134, P0154

Heated oxygen sensor 2 (rear) (min. voltage monitoring)

P0137, P0157

Heated oxygen sensor 2 (rear) (max. voltage monitoring)

P0138, P0158

Heated oxygen sensor 2 (rear) (response monitoring)

P0139, P0159

Heated oxygen sensor 2 (rear) (high voltage)

P0140, P0160

O2 SEN HEATER

Heated oxygen sensor 1 heater (front)

P0135, P0155

Heated oxygen sensor 2 heater (rear)

P0141, P0161

*: If completion of several SRTs is required, perform driving patterns (DTC confirmation procedure), one by one based on the priority
for models with CONSULT-II.

ON BOARD DIAGNOSTIC SYSTEM DESCRIPTION

Emission-related Diagnostic Information (Cont’d)

EC-62

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