
IntroductionNEEC0029The 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:
Diagnostic Trouble Code (DTC) Mode 3 of ISO 15031-5
Freeze Frame data Mode 2 of ISO 15031-5
System Readiness Test (SRT) code Mode 1 of ISO 15031-5
1st Trip Diagnostic Trouble Code (1st Trip DTC) Mode 7 of ISO 15031-5
1st Trip Freeze Frame data
Test values and Test limits Mode 6 of ISO 15031-5
Calibration ID Mode 9 of ISO 15031-6
The above information can be checked using procedures listed in the table below.
X: Applicable Ð: Not applicable
DTC 1st trip DTCFreeze Frame
data1st trip Freeze
Frame dataSRT code Test value
CONSULT-IIXXXXXÐ
GST X X*1 X Ð X X
*1: 1st trip DTCs for self-diagnoses concerning SRT items cannot be shown on the GST display.
The malfunction indicator (MI) 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-3101.)
Two Trip Detection LogicNEEC0030When a malfunction is detected for the first time, 1st trip DTC and 1st trip Freeze Frame data are stored in
the ECM memory. The MI 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 MI lights up. The MI lights up at the same time when the DTC is stored. <2nd
trip> The ªtripº in the ªTwo Trip Detection Logicº 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 MI,
and store DTC and Freeze Frame data, even in the 1st trip, as shown below.
X: Applicable Ð: Not applicable
ItemsMI DTC 1st trip DTC
1st trip 2nd trip
1st trip
displaying2nd trip
displaying1st trip
displaying2nd trip
displaying
Blinking Lighting up Blinking Lighting up
Misfire (Possible three way cata-
lyst damage) Ð DTC: P0300 -
P0304 is being detectedX ÐÐÐÐÐXÐ
Misfire (Possible three way cata-
lyst damage) Ð DTC: P0300 -
P0304 is being detectedÐÐ X ÐÐXÐÐ
Fail-safe items (Refer to
EC-3101.)Ð X Ð Ð X*1 Ð X*1 Ð
Except above Ð Ð Ð X Ð X X Ð
*1: Except ªECMº
Emission-related Diagnostic InformationNEEC0031DTC AND 1ST TRIP DTCNEEC0031S01The 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 MI will not light up (two trip detection logic). If the same malfunction is not detected in the 2nd
ON BOARD DIAGNOSTIC SYSTEM
DESCRIPTION
KA24DE (EURO OBD)
Introduction
EC-3049

trip (meeting the required driving pattern), the 1st trip DTC is cleared from the ECM memory. If the same mal-
function is detected in the 2nd trip, both the 1st trip DTC and DTC are stored in the ECM memory and the MI
lights up. In other words, the DTC is stored in the ECM memory and the MI lights up when the same malfunc-
tion occurs in two consecutive 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 MI 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 ªHOW TO
ERASE EMISSION-RELATED DIAGNOSTIC INFORMATIONº. Refer to EC-3060.
For malfunctions in which 1st trip DTCs are displayed, refer to EC-3058. 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 ISO 15031-5. 1st trip DTC detection occurs without lighting up the MI
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 ªWork Flowº procedure Step II, refer to page EC-3084. Then perform ªDTC Confirmation
Procedureº or ªOverall Function Checkº to try to duplicate the problem. If the malfunction is duplicated, the
item requires repair.
How to read DTC and 1st Trip DTCNEEC0031S0101DTC 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 etc.
These DTCs are prescribed by ISO 15031-5.
(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 avail-
able) is recommended.
A sample of CONSULT-II display for DTC is shown below. DTC or 1st trip DTC of a malfunction 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 ª0º.
If a 1st trip DTC is stored in the ECM, the time data will be ª[1t]º.
LEC028A
FREEZE FRAME DATA AND 1ST TRIP FREEZE FRAME DATANEEC0031S02The 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, throttle valve opening, 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-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-3073.
Only one set of freeze frame data (either 1st trip freeze frame data or freeze frame data) can be stored in the
ON BOARD DIAGNOSTIC SYSTEM
DESCRIPTION
KA24DE (EURO OBD)
Emission-related Diagnostic Information
EC-3050

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.
NVIS (Nissan Vehicle Immobilizer System Ð
NATS)
NEEC1601
SEF515Y
+If the security indicator lights up with the ignition switch in the ªONº position or ªNATS MALFUNC-
TIONº is displayed on ªSELF-DIAG RESULTSº screen, perform self-diagnostic results mode with
CONSULT-II using NATS program card. Refer to ªNVIS (Nissan Vehicle Immobilizer System Ð
NATS)º in EL section.
+Confirm no self-diagnostic results of NVIS (NATS) is displayed before touching ªERASEº in ªSELF-
DIAG RESULTSº mode with CONSULT-II.
+When replacing ECM, initialization of NVIS (NATS) system and registration of all NVIS (NATS) igni-
tion key IDs must be carried out with CONSULT-II using NATS program card.
Therefore, be sure to receive all keys from vehicle owner. Regarding the procedures of NVIS (NATS)
initialization and NVIS (NATS) ignition key ID registration, refer to CONSULT-II operation manual,
IVIS/NVIS.
Malfunction Indicator (MI)
DESCRIPTIONNEEC0032
SAT652J
The MI is located on the instrument panel.
1. The MI will light up when the ignition switch is turned ON without the engine running. This is a bulb check.
+If the MI does not light up, refer to EL section, ªWARNING LAMPSº or see EC-3396.
2. When the engine is started, the MI should go off.
If the MI remains on, the on board diagnostic system has detected an engine system malfunction.
On Board Diagnostic System FunctionNEEC0032S07The on board diagnostic system has the following four functions.
ON BOARD DIAGNOSTIC SYSTEM
DESCRIPTION
KA24DE (EURO OBD)
Emission-related Diagnostic Information
EC-3061

Fail-safe Chart=NEEC0040The ECM enters fail-safe mode if any of the following malfunctions is detected due to the open or short cir-
cuit. When the ECM enters the fail-safe mode, the MI illuminates.
DTC No.
Detected items Engine operating condition in fail-safe mode
CONSULT-II
GST
P0102
P0103Mass air flow sensor cir-
cuitEngine speed will not rise more than 2,400 rpm due to the fuel cut.
P0112
P0113Intake air temperature sen-
sorThe ECM functions on the assumption that the intake air temperature is 25ÉC (77ÉF).
P0117
P0118Engine coolant tempera-
ture sensor circuitEngine coolant temperature will be determined by ECM based on the time after turn-
ing ignition switch to ON or START.
CONSULT-II displays the engine coolant temperature decided by ECM.
ConditionEngine coolant temperature decided (CONSULT-
II display)
Just as ignition switch is turned to
ON or Start40ÉC (104ÉF)
More than approx. 4 minutes after
ignition ON or Start80ÉC (176ÉF)
Except as shown above40 - 80ÉC (104 - 176ÉF)
(Depends on the time)
P0122
P0123Throttle position sensor
circuitThrottle position will be determined based on the injected fuel amount and the engine
speed. Therefore, acceleration will be poor.
Condition Driving condition
When engine is idling Normal
When accelerating Poor acceleration
Unable to
access ECMECMECM fail-safe activating condition
The computing function of the ECM was judged to be malfunctioning.
When the fail-safe system activates (i.e., if the ECM detects a malfunction condition in
the CPU of ECM), the MI on the instrument panel lights to warn the driver.
However it is not possible to access ECM and DTC cannot be confirmed.
Engine control with fail-safe
When ECM fail-safe is operating, fuel injection, ignition timing, fuel pump operation
and IACV-AAC valve operation are controlled under certain limitations.
ECM fail-safe operation
Engine speedEngine speed will not rise more than 3,000
rpm
Fuel injection Simultaneous multiport fuel injection system
Ignition timing Ignition timing is fixed at the preset valve
Fuel pumpFuel pump relay is ªONº when engine is running
and ªOFFº when engine stalls
IACV-AAC valve Full open
Replace ECM, if ECM fail-safe condition is confirmed.
TROUBLE DIAGNOSIS Ð GENERAL
DESCRIPTION
KA24DE (EURO OBD)
Fail-safe Chart
EC-3101

DTC No. Malfunction is detected when ... Check Items (Possible Cause)
P0101
0101B) A low voltage from the sensor is sent to ECM* under
heavy load driving condition.+Harness or connectors
(The sensor circuit is open or shorted.)
+Intake air leaks
+Mass air flow sensor
*: When this malfunction is detected, the ECM enters fail-safe mode and the MI lights up.
FAIL-SAFE MODENEEC0053S01
Detected items Engine operating condition in fail-safe mode
Mass air flow sensor circuitEngine speed will not rise more than 2,400 rpm due to the fuel
cut.
DTC Confirmation ProcedureNEEC0054CAUTION:
Always drive vehicle at a safe speed.
NOTE:
If ªDTC Confirmation Procedureº has been previously conducted,
always turn ignition switch OFF and wait at least 5 seconds before
conducting the next test.
SEF174Y
PROCEDURE FOR MALFUNCTION ANEEC0054S03NOTE:
If engine will not start or stops soon, wait at least 10 seconds
with engine stopped (Ignition switch ªONº) instead of running
engine at idle speed.
With CONSULT-II
1) Turn ignition switch ON.
2) Select ªDATA MONITORº mode with CONSULT-II.
3) Start engine and warm it up to normal operating temperature.
4) Run engine for at least 10 seconds at idle speed.
5) If 1st trip DTC is detected, go to ªDiagnostic Procedureº,
EC-3147.
With GST
Follow the procedure ªWith CONSULT-IIº.
DTC P0101 MAF SENSORKA24DE (EURO OBD)
On Board Diagnosis Logic
EC-3144

DTC No. Malfunction is detected when ... Check Items (Possible Cause)
P0102
0102An excessively low voltage from the sensor is sent to
ECM* when engine is running.+Harness or connectors
(The sensor circuit is open or shorted.)
+Intake air leaks
+Mass air flow sensor
*: When this malfunction is detected, the ECM enters fail-safe mode and the MI lights up.
FAIL-SAFE MODENEEC1551S01
Detected items Engine operating condition in fail-safe mode
Mass air flow sensor circuitEngine speed will not rise more than 2,400 rpm due to the fuel
cut.
DTC Confirmation ProcedureNEEC1552CAUTION:
Always drive vehicle at a safe speed.
NOTE:
If ªDTC Confirmation Procedureº has been previously conducted,
always turn ignition switch OFF and wait at least 5 seconds before
conducting the next test.
SEF058Y
PROCEDURE FOR DTC P0103NEEC1552S01With CONSULT-II
1) Turn ignition switch ON.
2) Select ªDATA MONITORº mode with CONSULT-II.
3) Wait at least 6 seconds.
4) If 1st trip DTC is detected, go to ªDiagnostic Procedureº,
EC-3155.
If 1st trip DTC is not detected, go to next step.
5) Start engine and let it idle for at least 6 seconds.
6) If 1st trip DTC is detected, go to ªDiagnostic Procedureº,
EC-3155.
With GST
Follow the procedure ªWith CONSULT-IIº.
DTC P0102, P0103 MAF SENSORKA24DE (EURO OBD)
On Board Diagnosis Logic
EC-3152

FAIL-SAFE MODENEEC0067S01When the malfunction is detected, the ECM enters fail-safe mode and the MI lights up.
Engine operating condition in fail-safe mode
The ECM functions on the assumption that the intake air temperature is 25ÉC (77ÉF).
DTC Confirmation ProcedureNEEC0068NOTE:
If ªDTC Confirmation Procedureº has been previously conducted,
always turn ignition switch OFF and wait at least 5 seconds before
conducting the next test.
SEF058Y
With CONSULT-II
1) Turn ignition switch ON.
2) Select ªDATA MONITORº mode with CONSULT-II.
3) Wait at least 5 seconds.
4) If 1st trip DTC is detected, go to ªDiagnostic Procedureº,
EC-3163.
With GST
Follow the procedure ªWith CONSULT-IIº.
DTC P0112, P0113 IAT SENSORKA24DE (EURO OBD)
On Board Diagnosis Logic
EC-3161

On Board Diagnosis LogicNEEC0074
DTC No.Trouble diag-
nosis nameDTC detecting condition Possible cause
P0117
0117Engine cool-
ant tempera-
ture sensor
circuit low
inputAn excessively low voltage from the sensor is sent
to ECM.+Harness or connectors
(The sensor circuit is open or shorted.)
+Engine coolant temperature sensor
P0118
0118Engine cool-
ant tempera-
ture sensor
circuit high
inputAn excessively high voltage from the sensor is sent
to ECM.
FAIL-SAFE MODENEEC0074S01When the malfunction is detected, the ECM enters fail-safe mode and the MI lights up.
Detected items Engine operating condition in fail-safe mode
Engine coolant tempera-
ture sensor circuitEngine coolant temperature will be determined by ECM based on the time after turning ignition switch
to ON or START.
CONSULT-II displays the engine coolant temperature decided by ECM.
ConditionEngine coolant temperature decided (CONSULT-II
display)
Just as ignition switch is turned to ON or Start 40ÉC (104ÉF)
More than approx. 4 minutes after ignition ON or
Start80ÉC (176ÉF)
Except as shown above40 - 80ÉC (104 - 176ÉF)
(Depends on the time)
SEF058Y
DTC Confirmation ProcedureNEEC0075NOTE:
If ªDTC Confirmation Procedureº has been previously conducted,
always turn ignition switch OFF and wait at least 5 seconds before
conducting the next test.
With CONSULT-II
1) Turn ignition switch ON.
2) Select ªDATA MONITORº mode with CONSULT-II.
3) Wait at least 5 seconds.
4) If 1st trip DTC is detected, go to ªDiagnostic Procedureº,
EC-3168.
With GST
Follow the procedure ªWith CONSULT-IIº.
DTC P0117, P0118 ECT SENSORKA24DE (EURO OBD)
On Board Diagnosis Logic
EC-3166