Infiniti QX56 (Z62). Manual - part 518

EC-50

< SYSTEM DESCRIPTION >

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OPERATION

- Engine coolant temperature is slightly higher than the normal operating temperature. Then CRUISE indica-

tor lamp is blinked slowly.
NOTE:
 Engine coolant temperature decreases to the normal operating temperature, CRUISE indicator lamp stop
blinking and the cruise operation is able to work.

- Malfunction for some self-diagnoses regarding ASCD system. CRUISE indicator lamp is blinked quickly.
• When ASCD MAIN switch is turned to OFF during the cruise control driving, all of ASCD operations is can-

celed and vehicle speed memory is erased.

ON BOARD DIAGNOSTIC (OBD) SYSTEM

EC-51

< SYSTEM DESCRIPTION >

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ON BOARD DIAGNOSTIC (OBD) SYSTEM

Diagnosis Description

INFOID:0000000006217720

This system is an on board diagnostic system that records exhaust emission-related diagnostic information
and detects a sensors/actuator-related malfunction. A malfunction is indicated by the malfunction indicator
lamp (MIL) and stored in ECU memory as a DTC. The diagnostic information can be obtained with the diag-
nostic tool (GST: Generic Scan Tool).

GST (Generic Scan Tool)

INFOID:0000000006217721

When GST is connected with a data link connector equipped on the vehicle side, it will communicate with the
control unit equipped in the vehicle and then enable various kinds of diagnostic tests. Refer to 

GI-48, "Descrip-

tion"

.

NOTE:
Service $0A is not applied for regions where it is not mandated.

EC-52

< SYSTEM DESCRIPTION >

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DIAGNOSIS SYSTEM (ECM)

DIAGNOSIS SYSTEM (ECM)

DIAGNOSIS DESCRIPTION

DIAGNOSIS DESCRIPTION : 1st Trip Detection Logic and Two Trip Detection Logic

INFOID:0000000006217722

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 illuminate 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 illuminates. The MIL illuminates 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 per-
formed during vehicle operation. Specific on board diagnostic items will cause the ECM to illuminate or blink
the MIL, and store DTC and Freeze Frame data, even in the 1st trip, as shown below.

×

: Applicable

—: Not applicable

DIAGNOSIS DESCRIPTION : DTC and Freeze Frame Data

INFOID:0000000006217723

DTC AND 1ST TRIP DTC

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 recur, the 1st trip DTC
will not be displayed.
If a malfunction is detected during the 1st trip, the 1st trip DTC is saved 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 saved 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 consec-
utive 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 during the
1st trip, the DTC and 1st trip DTC are stored in the ECM memory.
For malfunctions in which 1st trip DTCs are displayed, refer to 

EC-98, "DTC Index"

. These items are required

by legal regulations to continuously monitor the system/component. In addition, the items monitored non-con-
tinuously are also displayed on CONSULT-III.
1st trip DTC is specified in Service $07 of SAE J1979/ISO 15031-5. 1st trip DTC detection occurs without illu-
minating the MIL and therefore does not warn the driver of a malfunction.
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 2, refer to 

EC-135, "Work Flow"

. Then perform DTC Confirma-

tion Procedure or Component Function Check to try to duplicate the malfunction. If the malfunction is dupli-
cated, the item requires repair.

FREEZE FRAME DATA AND 1ST TRIP FREEZE FRAME DATA

The ECM records the driving conditions such as fuel system status, calculated load value, engine coolant tem-
perature, short term fuel trim, long term fuel trim, engine speed, vehicle speed, absolute throttle position, base
fuel schedule and intake air temperature 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.
The data, stored together with the DTC data, are called freeze frame data and displayed on CONSULT-III or
GST. The 1st trip freeze frame data can only be displayed on the CONSULT-III screen.

Items

MIL

DTC

1st trip DTC

1st trip

2nd trip 

1st trip 

displaying

2nd trip 

displaying

1st trip 

displaying

2nd trip 

displaying

Blinking

Illuminate

Blinking

Illuminate

Misfire (Possible three way catalyst 
damage) — DTC: P0300 - P0308 is 
being detected

×

—

—

—

—

—

×

—

Misfire (Possible three way catalyst 
damage) — DTC: P0300 - P0308 is 
being detected

—

—

×

—

—

×

—

—

One trip detection diagnoses (Re-
fer to 

EC-98, "DTC Index"

.)

—

×

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—

×

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Except above

—

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—

×

—

×

×

—

DIAGNOSIS SYSTEM (ECM)

EC-53

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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 priority
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.

For example, the EGR malfunction (Priority: 2) was detected and the freeze frame data was saved 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 mem-
ory is erased.

DIAGNOSIS DESCRIPTION : Counter System

INFOID:0000000006217724

RELATIONSHIP BETWEEN MIL, 1ST TRIP DTC, DTC, AND DETECTABLE ITEMS

• When a malfunction is detected for the first time, the 1st trip DTC and the 1st trip freeze frame data are

stored in the ECM memory.

• When the same malfunction is detected in two consecutive trips, the DTC and the freeze frame data are

stored in the ECM memory, and the MIL will come on.

• The MIL will turn OFF after the vehicle is driven 3 times (driving pattern B) with no malfunction. The drive is

counted only when the recorded driving pattern is met (as stored in the ECM). If another malfunction occurs
while counting, the counter will reset.

• The DTC and the freeze frame data will be stored until the vehicle is driven 40 times (driving pattern A) with-

out the same malfunction recurring (except for Misfire and Fuel Injection System). For Misfire and Fuel Injec-
tion System, the DTC and freeze frame data will be stored until the vehicle is driven 80 times (driving pattern
C) without the same malfunction recurring. The “TIME” in “SELF-DIAGNOSTIC RESULTS” mode of CON-
SULT-III will count the number of times the vehicle is driven.

• The 1st trip DTC is not displayed when the self-diagnosis results in OK for the 2nd trip.

COUNTER SYSTEM CHART

For details about patterns B and C under “Fuel Injection System” and “Misfire”, see “EXPLANATION FOR
DRIVING PATTERNS FOR “MISFIRE <EXHAUST QUALITY DETERIORATION>”, “FUEL INJECTION SYS-
TEM”.
For details about patterns A and B under Other, see “EXPLANATION FOR DRIVING PATTERNS FOR “MIS-
FIRE <EXHAUST QUALITY DETERIORATION>”, “FUEL INJECTION SYSTEM”.
• *1: Clear timing is at the moment OK is detected.
• *2: Clear timing is when the same malfunction is detected in the 2nd trip.

Relationship Between MIL, DTC, 1st Trip DTC and Driving Patterns for “Misfire <Exhaust Quality De-
terioration>”, “Fuel Injection System”

Priority

Items

1

Freeze frame data

Misfire — DTC: P0300 - P0308
Fuel Injection System Function — DTC: P0171, P0172, P0174, P0175

2

Except the above items

3

1st trip freeze frame data

Items

Fuel Injection System

Misfire

Other

MIL (turns OFF)

3 (pattern B)

3 (pattern B)

3 (pattern B)

DTC, Freeze Frame Data (no display)

80 (pattern C)

80 (pattern C)

40 (pattern A)

1st Trip DTC (clear)

1 (pattern C), *1

1 (pattern C), *1

1 (pattern B)

1st Trip Freeze Frame Data (clear)

*1, *2

*1, *2

1 (pattern B)