Infiniti FX35, FX50 (S51). Manual - part 791

ON BOARD DIAGNOSTIC (OBD) SYSTEM

EC-705

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ON BOARD DIAGNOSTIC (OBD) SYSTEM

Diagnosis Description

INFOID:0000000005237213

INTRODUCTION

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:

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

×

: Applicable

—: Not applicable

*: When DTC and 1st trip DTC simultaneously appear on the display, they cannot be clearly distinguished from each other.

The malfunction indicator lamp (MIL) on the instrument panel illuminates 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-1175, "Fail-safe"

.)

TWO TRIP DETECTION LOGIC

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

DTC AND FREEZE FRAME DATA

DTC and 1st Trip DTC

Emission-related diagnostic information

Diagnostic service

Diagnostic Trouble Code (DTC)

Service $03 of SAE J1979/ISO 15031-5

Freeze Frame data

Service $02 of SAE J1979/ISO 15031-5

System Readiness Test (SRT) code

Service $01 of SAE J1979/ISO 15031-5

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

Service $07 of SAE J1979/ISO 15031-5

1st Trip Freeze Frame data

—

Test values and Test limits

Service $06 of SAE J1979/ISO 15031-5

Calibration ID

Service $09 of SAE J1979/ISO 15031-5

DTC

1st trip DTC

Freeze 

Frame data

1st trip Freeze 

Frame data

SRT code

SRT status

Test value

CONSULT-III

×

×

×

×

×

×

—

GST

×

×

×

—

×

×

×

ECM

×

×

*

—

—

—

×

—

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-1179, "DTC Index"

.)

—

×

—

—

×

—

—

—

Except above

—

—

—

×

—

×

×

—

EC-706

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ON BOARD DIAGNOSTIC (OBD) SYSTEM

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
illuminate (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 illuminates. In other
words, the DTC is stored in the ECM memory and the MIL illuminates when the same malfunction occurs in
two consecutive trips. If a 1st trip DTC is saved 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 illuminate the MIL
during 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
DTC and 1st Trip DTC.
For malfunctions in which 1st trip DTCs are displayed, refer to 

EC-1179, "DTC Index"

. 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-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. 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 2, refer to 

EC-572, "Work Flow"

. Then perform DTC CONFIR-

MATION PROCEDURE or Component Function Check to try to duplicate the malfunction. If the malfunction is
duplicated, 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, not on the GST.
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. Procedures for clearing the ECM memory are described in “How to Erase DTC and 1st Trip
DTC”.

How to Read DTC and 1st Trip DTC

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

 With CONSULT-III

CONSULT-III displays the DTC in “SELF DIAGNOSTIC RESULT” mode. Examples: P0340, P0850, P1148,
etc.

Priority

Items

1

Freeze frame data

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

2

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

3

1st trip freeze frame data

ON BOARD DIAGNOSTIC (OBD) SYSTEM

EC-707

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These DTCs are prescribed by SAE J2012./ISO 15031-6
(CONSULT-III also displays the malfunctioning component or system.)
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].

 With GST

GST (Generic Scan Tool) displays the DTC in Diagnostic Service $03. Examples: P0340, P0850, P1148, etc.
These DTCs are prescribed by SAE J2012.
1st trip DTC is displayed in Diagnostic Service $07.

 No Tools

The number of blinks of the MIL in the Diagnostic Test Mode II (Self-Diagnostic Results) indicates the DTC.
Example: 0340, 0850, 1148, etc.
These DTCs are controlled by NISSAN.
NOTE:
• 1st trip DTC No. is the same as DTC No.
• Output of a DTC indicates a malfunction. However, GST and the Diagnostic Test Mode II do not indi-

cate whether the malfunction is still occurring or has occurred in the past and has returned to nor-
mal. CONSULT-III can identify malfunction status. Therefore, using CONSULT-III (if available) is
recommended.

How to Erase DTC and 1st Trip DTC

 With CONSULT-III

NOTE:
• If the ignition switch stays ON after repair work, be sure to turn ignition OFF once.

Wait at least 10 seconds and then turn it ON (engine stopped) again.

• If the DTC is not for A/T related items (see 

EC-1179, "DTC Index"

), skip step 1.

1.

Erase DTC in TCM. Refer to 

TM-242, "Diagnosis Description"

.

2.

Select “ENGINE” with CONSULT-III.

3.

Select “SELF-DIAG RESULTS”.

4.

Touch “ERASE”. (DTC in ECM will be erased.)

 With GST

NOTE:
• If the ignition switch stays ON after repair work, be sure to turn ignition OFF once.

Wait at least 10 seconds and then turn it ON (engine stopped) again.

1.

Select Diagnostic Service $04 with GST (Generic Scan Tool).

 No Tools

NOTE:
• If the ignition switch stays ON after repair work, be sure to turn ignition switch OFF once.

Wait at least 10 seconds and then turn it ON (engine stopped) again.

1.

Erase DTC in ECM. Refer to How To ERASE DIAGNOSTIC TEST MODE II (SELF-DIAGNOSTIC
RESULTS).

NOTE:
• If the battery is disconnected, the emission-related diagnostic information will be cleared within 24

hours.

• The following data are cleared when the ECM memory is erased.
- Diagnostic trouble codes
- 1st trip diagnostic trouble codes
- Freeze frame data
- 1st trip freeze frame data
- System readiness test (SRT) codes
- Test values
• Actual work procedures are explained using a DTC as an example. Be careful so that not only the DTC, but

all of the data listed above, are cleared from the ECM memory during work procedures.

SYSTEM READINESS TEST (SRT) CODE

System Readiness Test (SRT) code is specified in Service $01 of SAE J1979/ISO 15031-5.
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.

EC-708

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ON BOARD DIAGNOSTIC (OBD) SYSTEM

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 mem-
ory 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.

SRT Item

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

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

SRT Set Timing

SRT is set as “CMPLT” after self-diagnosis has been performed one or more times. Completion of SRT is
done regardless of whether the result is OK or NG. The set timing is different between OK and NG results and
is shown in the table below.

SRT item

(CONSULT-III indication)

Performance 

Priority*

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

Corresponding 

DTC No.

CATALYST

2

Three way catalyst function

P0420, P0430

EVAP SYSTEM

2

EVAP control system purge flow monitoring

P0441

1

EVAP control system

P0442

2

EVAP control system

P0456

HO2S

2

Air fuel ratio (A/F) sensor 1

P0133, P0153

Heated oxygen sensor 2

P0137, P0157

Heated oxygen sensor 2

P0138, P0158

Heated oxygen sensor 2

P0139, P0159

Self-diagnosis result

Example

Diagnosis

Ignition cycle 

←

 ON 

→

OFF

←

 ON 

→

OFF

←

 ON 

→

OFF

←

 ON 

→

All OK

Case 1

P0400

OK (1)

— (1)

OK (2)

— (2)

P0402

OK (1)

— (1)

— (1)

OK (2)

P1402

OK (1)

OK (2)

— (2)

— (2)

SRT of EGR

“CMPLT”

“CMPLT”

“CMPLT”

“CMPLT”

Case 2

P0400

OK (1)

— (1)

— (1)

— (1)

P0402

— (0)

— (0)

OK (1)

— (1)

P1402

OK (1)

OK (2)

— (2)

— (2)

SRT of EGR

“INCMP”

“INCMP”

“CMPLT”

“CMPLT”