2001 INFINITI QX4 check engine light

Emission-related Diagnostic InformationNBEC0031DTC AND 1ST TRIP DTCNBEC0031S01The 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 ªHOW TO
ERASE EMISSION-RELATED DIAGNOSTIC INFORMATIONº, 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 ªWork Flowº procedure Step II, refer to EC-99. Then perform ªDTC Confirmation Proce-
dureº 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 DTCNBEC0031S0101DTC 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.)
I1st trip DTC No. is the same as DTC No.
IOutput 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 ª0º.
If a 1st trip DTC is stored in the ECM, the time data will be ª[1t]º.
SEF992X
FREEZE FRAME DATA AND 1ST TRIP FREEZE FRAME DATANBEC0031S02The 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

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.
IVIS (INFINITI VEHICLE IMMOBILIZER SYSTEM Ð NATS)NBEC0031S08
SEF515Y
IIf 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 ªIVIS (Infiniti Vehicle Immobilizer System Ð NATS)º
in EL section.
IConfirm no self-diagnostic results of IVIS (NATS) is displayed before touching ªERASEº in ªSELF-
DIAG RESULTSº mode with CONSULT-II.
IWhen replacing ECM, initialization of IVIS (NATS) system and registration of all IVIS (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 IVIS (NATS)
initialization and IVIS (NATS) ignition key ID registration, refer to CONSULT-II operation manual,
IVIS/NVIS.
Malfunction Indicator Lamp (MIL)
DESCRIPTIONNBEC0032
SEF217U
The MIL is located on the instrument panel.
1. The MIL will light up when the ignition switch is turned ON without the engine running. This is a bulb check.
IIf the MIL does not light up, refer to EL-114, ªWARNING LAMPSº or see EC-648.
2. When the engine is started, the MIL should go off.
If the MIL remains on, the on board diagnostic system has detected an engine system malfunction.
On Board Diagnostic System FunctionNBEC0032S01The on board diagnostic system has the following two functions.
ON BOARD DIAGNOSTIC SYSTEM DESCRIPTION
Emission-related Diagnostic Information (Cont'd)
EC-74

Diagnostic Test
ModeKEY and ENG.
StatusFunction Explanation of Function
Mode I Ignition switch in
ªONº position
Engine stopped
BULB CHECK This function checks the MIL bulb for damage (blown,
open circuit, etc.).
If the MIL does not come on, check MIL circuit.
Engine running
MALFUNCTION
WARNINGThis is a usual driving condition. When a malfunction is
detected twice in two consecutive driving cycles (two trip
detection logic), the MIL will light up to inform the driver
that a malfunction has been detected.
The following malfunctions will light up or blink the MIL in
the 1st trip.
ICoolant overtemperature enrichment protection
IªMisfire (Possible three way catalyst damage)º
IªClosed loop controlº
IFail-safe mode
Diagnostic Test Mode I Ð Bulb CheckNBEC0032S03In this mode, the MIL on the instrument panel should stay ON. If it remains OFF, check the bulb. Refer to
EL-114, ªWARNING LAMPSº or see EC-648.
Diagnostic Test Mode I Ð Malfunction WarningNBEC0032S04
MIL Condition
ON When the malfunction is detected or the ECM's CPU is malfunctioning.
OFF No malfunction.
OBD System Operation ChartNBEC0033RELATIONSHIP BETWEEN MIL, 1ST TRIP DTC, DTC, AND DETECTABLE ITEMSNBEC0033S01IWhen 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.
IWhen 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. For details, refer to ªTwo Trip Detection Logicº on
EC-59.
IThe MIL will go off after the vehicle is driven 3 times 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.
IThe DTC and the freeze frame data will be stored until the vehicle is driven 40 times (driving pattern A)
without the same malfunction recurring (except for Misfire and Fuel Injection System). For Misfire and Fuel
Injection System, the DTC and freeze frame data will be stored until the vehicle is driven 80 times (driv-
ing pattern C) without the same malfunction recurring. The ªTIMEº in ªSELF-DIAGNOSTIC RESULTSº
mode of CONSULT-II will count the number of times the vehicle is driven.
IThe 1st trip DTC is not displayed when the self-diagnosis results in ªOKº for the 2nd trip.
SUMMARY CHARTNBEC0033S02
Items Fuel Injection System Misfire Other
MIL (goes 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)
GI
MA
EM
LC
FE
AT
TF
PD
AX
SU
BR
ST
RS
BT
HA
SC
EL
IDX
ON BOARD DIAGNOSTIC SYSTEM DESCRIPTION
Malfunction Indicator Lamp (MIL) (Cont'd)
EC-75

Monitored item [Unit]ECM
input
signalsMain
signalsDescription Remarks
A/F ALPHA-B1 [%]q
IIndicates the mean value of the air-fuel ratio
feedback correction factor per cycle.IWhen the engine is running, specifi-
cation range is indicated.
IThis data also includes the data for
the air-fuel ratio learning control. A/F ALPHA-B2 [%]q
NOTE:
IAny monitored item that does not match the vehicle being diagnosed is deleted from the display automatically.
IRegarding R50 model, ªB1º indicates bank 1 and ªB2º indicates bank 2.
ACTIVE TEST MODENBEC0034S07
TEST ITEM CONDITION JUDGEMENT CHECK ITEM (REMEDY)
FUEL INJECTIONIEngine: Return to the original
trouble condition
IChange the amount of fuel injec-
tion using CONSULT-II.If trouble symptom disappears, see
CHECK ITEM.IHarness and connector
IFuel injectors
IHeated oxygen sensor
IGNITION TIMINGIEngine: Return to the original
trouble condition
ITiming light: Set
IRetard the ignition timing using
CONSULT-II.If trouble symptom disappears, see
CHECK ITEM.IAdjust initial ignition timing
IACV-AAC/V
OPENINGIEngine: After warming up, idle
the engine.
IChange the IACV-AAC valve
opening percent using CON-
SULT-II.Engine speed changes according
to the opening percent.IHarness and connector
IIACV-AAC valve
POWER BAL-
ANCEIEngine: After warming up, idle
the engine.
IA/C switch ªOFFº
IShift lever ªNº
ICut off each injector signal one
at a time using CONSULT-II.Engine runs rough or dies.IHarness and connector
ICompression
IInjectors
IPower transistor
ISpark plugs
IIgnition coils
ENG COOLANT
TEMPIEngine: Return to the original
trouble condition
IChange the engine coolant tem-
perature using CONSULT-II.If trouble symptom disappears, see
CHECK ITEM.IHarness and connector
IEngine coolant temperature sen-
sor
IFuel injectors
FUEL PUMP
RELAYIIgnition switch: ON
(Engine stopped)
ITurn the fuel pump relay ªONº
and ªOFFº using CONSULT-II
and listen to operating sound.Fuel pump relay makes the operat-
ing sound.IHarness and connector
IFuel pump relay
VIAS SOL VALVEIIgnition switch: ON
ITurn solenoid valve ªONº and
ªOFFº with CONSULT-II and lis-
ten for operating sound.Solenoid valve makes an operating
sound.IHarness and connector
ISolenoid valve
SWIRL CONT
S O L VA LV EIIgnition switch: ON
ITurn solenoid valve ªONº and
ªOFFº with CONSULT-II and lis-
ten for operating sound.Solenoid valve makes an operating
sound.IHarness and connector
ISolenoid valve
PURG VOL
CONT/VIEngine: After warming up, run
engine at 1,500 rpm.
IChange the EVAP canister purge
volume control solenoid valve
opening percent using CON-
SULT-II.Engine speed changes according
to the opening percent.IHarness and connector
ISolenoid valve
GI
MA
EM
LC
FE
AT
TF
PD
AX
SU
BR
ST
RS
BT
HA
SC
EL
IDX
ON BOARD DIAGNOSTIC SYSTEM DESCRIPTION
CONSULT-II (Cont'd)
EC-91

28 CHECK IGNITION TIMING
1. Start engine and warm it up to normal operating temperature.
2. Check ignition timing at idle using a timing light.
SEF572X
Ignition timing:
15ɱ5É BTDC (in ªPº or ªNº position)
OK or NG
OK©GO TO 36.
NG©GO TO 29.
29 CHECK TIMING CHAIN INSTALLATION
Check timing chain installation. Refer to EM-29, ªInstallationº.
OK or NG
OK©GO TO 27.
NG©1. Repair the timing chain installation.
2. GO TO 22.
30 CHECK IGNITION TIMING
1. Start engine and let it idle.
2. Check ignition timing at idle using a timing light.
SEF572X
Ignition timing:
15ɱ5É BTDC (in ªPº or ªNº position)
OK or NG
OK©GO TO 36.
NG©GO TO 31.
TROUBLE DIAGNOSIS Ð BASIC INSPECTION
Basic Inspection (Cont'd)
EC-114

SYMPTOM
Reference
section
HARD/NO START/RESTART (EXCP. HA)
ENGINE STALL
HESITATION/SURGING/FLAT SPOT
SPARK KNOCK/DETONATION
LACK OF POWER/POOR ACCELERATION
HIGH IDLE/LOW IDLE
ROUGH IDLE/HUNTING
IDLING VIBRATION
SLOW/NO RETURN TO IDLE
OVERHEATS/WATER TEMPERATURE HIGH
EXCESSIVE FUEL CONSUMPTION
EXCESSIVE OIL CONSUMPTION
BATTERY DEAD (UNDER CHARGE)
Warranty symptom code AA AB AC AD AE AF AG AH AJ AK AL AM HA
IVIS (INFINITI Vehicle Immobilizer System Ð
NATS)11EC-74 or EL
section
1 - 6: The numbers refer to the order of inspection.
CONSULT-II Reference Value in Data Monitor
Mode
NBEC0042Remarks:
ISpecification data are reference values.
ISpecification data are output/input values which are detected or supplied by the ECM at the connector.
* Specification data may not be directly related to their components signals/values/operations.
i.e. Adjust ignition timing with a timing light before monitoring IGN TIMING, because the monitor may show the specification data in
spite of the ignition timing not being adjusted to the specification data. This IGN TIMING monitors the data calculated by the ECM
according to the signals input from the camshaft position sensor and other ignition timing related sensors.
IIf the real-time diagnosis results are NG and the on board diagnostic system results are OK when diagnosing the mass air flow sensor,
first check to see if the fuel pump control circuit is normal.
MONITOR ITEM CONDITION SPECIFICATION
ENG SPEED
CKPS´RPM (POS)ITachometer: Connect
IRun engine and compare tachometer indication with the CONSULT-II
value.Almost the same speed as
the CONSULT-II value.
POS COUNTIEngine: Running 179 - 181
MAS A/F SE-B1IEngine: After warming up
IAir conditioner switch: ªOFFº
IShift lever: ªNº
INo-loadIdle 1.2 - 1.8V
2,500 rpm 1.6 - 2.2V
COOLAN TEMP/SIEngine: After warming up More than 70ÉC (158ÉF)
HO2S1 (B1)
HO2S1 (B2)
IEngine: After warming upMaintaining engine speed at 2,000
rpm0 - 0.3V+,Approx. 0.6 -
1.0V
HO2S1 MNTR (B1)
HO2S1 MNTR (B2)LEAN+,RICH
Changes more than 5 times
during 10 seconds.
HO2S2 (B1)
HO2S2 (B2)
IEngine: After warming upMaintaining engine speed at 2,000
rpm0 - 0.3V+,Approx. 0.6 -
1.0V
HO2S2 MNTR (B1)
HO2S2 MNTR (B2)LEAN+,RICH
TROUBLE DIAGNOSIS Ð GENERAL DESCRIPTION
Symptom Matrix Chart (Cont'd)
EC-122

On Board Diagnosis LogicNBEC0169With the Air/Fuel Mixture Ratio Self-Learning Control, the actual
mixture ratio can be brought closely to the theoretical mixture ratio
based on the mixture ratio feedback signal from the heated oxygen
sensors 1 (front). The ECM calculates the necessary compensation
to correct the offset between the actual and the theoretical ratios.
In case the amount of the compensation value is extremely large
(The actual mixture ratio is too lean.), the ECM judges the condi-
tion as the fuel injection system malfunction and light up the MIL
(2 trip detection logic).
Sensor Input Signal to ECMECM func-
tionActuator
Heated oxygen sensors 1 (front)Density of oxygen in exhaust gas
(Mixture ratio feedback signal)Fuel injec-
tion controlInjectors
Malfunction is detected when fuel injection system does not oper-
ate properly, the amount of mixture ratio compensation is too large.
(The mixture ratio is too lean.)
Possible CauseNBEC0487IIntake air leaks
IHeated oxygen sensor 1 (front)
IInjectors
IExhaust gas leaks
IIncorrect fuel pressure
ILack of fuel
IMass air flow sensor
SEF968Y
DTC Confirmation ProcedureNBEC0170NOTE:
If ªDTC Confirmation Procedureº has been previously conducted,
always turn ignition switch ªOFFº and wait at least 10 seconds
before conducting the next test.
WITH CONSULT-IINBEC0170S011) Start engine and warm it up to normal operating temperature.
2) Turn ignition switch ªOFFº and wait at least 10 seconds.
3) Turn ignition switch ªONº and select ªSELF-LEARN CON-
TROLº in ªWORK SUPPORTº mode with CONSULT-II.
4) Clear the self-learning control coefficient by touching ªCLEARº.
5) Select ªDATA MONITORº mode with CONSULT-II.
6) Start engine again and let it idle for at least 10 minutes.
The 1st trip DTC P0171 or P0174 should be detected at this
stage, if a malfunction exists. If so, go to ªDiagnostic
Procedureº, EC-298.
7) If it is difficult to start engine at step 6, the fuel injection sys-
tem has a malfunction, too.
8) Crank engine while depressing accelerator pedal. If engine
starts, go to ªDiagnostic Procedureº, EC-298. If engine does
not start, check exhaust and intake air leak visually.
DTC P0171 (RIGHT, -B1), P0174 (LEFT, -B2) FUEL INJECTION SYSTEM
FUNCTION (LEAN)
On Board Diagnosis Logic
EC-294

On Board Diagnosis LogicNBEC0173With the Air/Fuel Mixture Ratio Self-Learning Control, the actual
mixture ratio can be brought closely to the theoretical mixture ratio
based on the mixture ratio feedback signal from the heated oxygen
sensors 1 (front). The ECM calculates the necessary compensation
to correct the offset between the actual and the theoretical ratios.
In case the amount of the compensation value is extremely large
(The actual mixture ratio is too rich.), the ECM judges the condi-
tion as the fuel injection system malfunction and light up the MIL
(2 trip detection logic).
Sensor Input Signal to ECMECM func-
tionActuator
Heated oxygen sensors 1 (front)Density of oxygen in exhaust gas
(Mixture ratio feedback signal)Fuel injec-
tion controlInjectors
Malfunction is detected when fuel injection system does not oper-
ate properly, the amount of mixture ratio compensation is too large.
(The mixture ratio is too rich.)
Possible CauseNBEC0488IHeated oxygen sensor 1 (front)
IInjectors
IExhaust gas leaks
IIncorrect fuel pressure
IMass air flow sensor
SEF968Y
DTC Confirmation ProcedureNBEC0174NOTE:
If ªDTC Confirmation Procedureº has been previously conducted,
always turn ignition switch ªOFFº and wait at least 10 seconds
before conducting the next test.
WITH CONSULT-IINBEC0174S011) Start engine and warm it up to normal operating temperature.
2) Turn ignition switch ªOFFº and wait at least 10 seconds.
3) Turn ignition switch ªONº and select ªSELF-LEARN CON-
TROLº in ªWORK SUPPORTº mode with CONSULT-II.
4) Clear the self-learning control coefficient by touching ªCLEARº.
5) Select ªDATA MONITORº mode with CONSULT-II.
6) Start engine again and let it idle for at least 10 minutes.
The 1st trip DTC P0172, P0175 should be detected at this
stage, if a malfunction exists. If so, go to ªDiagnostic
Procedureº, EC-306.
7) If it is difficult to start engine at step 6, the fuel injection sys-
tem has a malfunction, too.
8) Crank engine while depressing accelerator pedal.
If engine starts, go to ªDiagnostic Procedureº, EC-306. If
engine does not start, remove ignition plugs and check for
fouling, etc.
DTC P0172 (RIGHT, -B1), P0175 (LEFT, -B2) FUEL INJECTION SYSTEM
FUNCTION (RICH)
On Board Diagnosis Logic
EC-302