2001 INFINITI QX4 Ac system

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

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
1Freeze frame data Misfire Ð DTC: P0300 - P0306
Fuel Injection System Function Ð DTC: P0171, P0172, P0174, P0175
2 Except the above items (Includes A/T related items)
3 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 ªHOW TO ERASE EMISSION-
RELATED DIAGNOSTIC INFORMATIONº, EC-72.
SYSTEM READINESS TEST (SRT) CODENBEC0031S03System 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 ªINCMPº,
use the information in this Service Manual to set the SRT to ªCMPLTº.
In most cases the ECM will automatically complete its self-diagnosis cycle during normal usage, and the SRT
status will indicate ªCMPLTº for each application system. Once set as ªCMPLTº, the SRT status remains
ªCMPLTº 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 ªINCMPº for these items.
NOTE:
The SRT will also indicate ªINCMPº 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 ªCMPLTº for all test items, the inspector will con-
tinue with the emissions test. However, if the SRT indicates ªINCMPº for one or more of the SRT items the
vehicle is returned to the customer untested.
NOTE:
If MIL is ªONº during the state emissions inspection, the vehicle is also returned to the customer untested even
though the SRT indicates ªCMPLTº for all test items. Therefore, it is important to check SRT (ªCMPLTº) and
DTC (No DTCs) before the inspection.
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ON BOARD DIAGNOSTIC SYSTEM DESCRIPTION
Emission-related Diagnostic Information (Cont'd)
EC-61

SRT Item=NBEC0031S0310The table below shows required self-diagnostic items to set the SRT to ªCMPLTº.
SRT item
(CONSULT-II indica-
tion)Perfor-
mance Pri-
ority*Required self-diagnostic items to set the SRT to ªCMPLTºCorresponding
DTC No.
CATALYST 3 Three way catalyst function P0420, P0430
EVAP SYSTEM 2 EVAP control system (small leak) (negative pressure) P0440
3 EVAP control system (very small leak) (negative pressure)/
(positive pressure)P1441
3 EVAP control system purge flow monitoring P1447
O2 SENSOR 3 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 3 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

SRT Set Timing=NBEC0031S0311SRT is set as ªCMPLTº 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.
Self-diagnosis resultExample
DiagnosisIgnition cycle
+ON,OFF+ON,OFF+ON,OFF+ON,
All OK Case 1 P0400 OK (1) Ð (1) OK (2) Ð (2)
P0402 OK (1) Ð (1) Ð (1) OK (2)
P1402 OK (1) OK (2) Ð (2) Ð (2)
SRT of EGR ªCMPLTº ªCMPLTº ªCMPLTº ªCMPLTº
Case 2 P0400 OK (1) Ð (1) Ð (1) Ð (1)
P0402 Ð (0) Ð (0) OK (1) Ð (1)
P1402 OK (1) OK (2) Ð (2) Ð (2)
SRT of EGR ªINCMPº ªINCMPº ªCMPLTº ªCMPLTº
NG exists Case 3 P0400 OK OK Ð Ð
P0402 Ð Ð Ð Ð
P1402 NG Ð NGNG
(Consecutive NG)
(1st trip)
DTC1st trip DTC Ð 1st trip DTCDTC
(= MIL ªONº)
SRT of EGR ªINCMPº ªINCMPº ªINCMPº ªCMPLTº
OK: Self-diagnosis is carried out and the result is OK.
NG: Self-diagnosis is carried out and the result is NG.
Ð: Self-diagnosis is not carried out.
When all SRT related self-diagnoses showed OK results in a single cycle (Ignition OFF-ON-OFF), the SRT
will indicate ªCMPLTº.,Case 1 above
When all SRT related self-diagnoses showed OK results through several different cycles, the SRT will indi-
cate ªCMPLTº at the time the respective self-diagnoses have at least one OK result.,Case 2 above
If one or more SRT related self-diagnoses showed NG results in 2 consecutive cycles, the SRT will also indi-
cate ªCMPLTº.,Case 3 above
The table above shows that the minimum number of cycles for setting SRT as ªINCMPº is one (1) for each
self-diagnosis (Case1&2)ortwo(2)foroneofself-diagnoses (Case 3). However, in preparation for the state
emissions inspection, it is unnecessary of each self-diagnosis to be executed twice (Case 3) for the following
reasons:
IThe SRT will indicate ªCMPLTº at the time the respective self-diagnoses have one (1) OK result.
IThe emissions inspection requires ªCMPLTº of the SRT only with OK self-diagnosis results.
IWhen, during SRT driving pattern, 1st trip DTC (NG) is detected prior to ªCMPLTº of SRT, the self-diag-
nosis memory must be erased from ECM after repair.
IIf the 1st trip DTC is erased, all the SRT will indicate ªINCMPº.
NOTE:
SRT can be set as ªCMPLTº together with the DTC(s). Therefore, DTC check must always be carried out prior
to the state emission inspection even though the SRT indicates ªCMPLTº.
SRT Service ProcedureNBEC0031S0312If a vehicle has failed the state emissions inspection due to one or more SRT items indicating ªINCMPº, review
the flowchart diagnostic sequence on the next page.
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ON BOARD DIAGNOSTIC SYSTEM DESCRIPTION
Emission-related Diagnostic Information (Cont'd)
EC-63

SEF170Z
*1 EC-60 *2 EC-64 *3 EC-65
How to Display SRT CodeNBEC0031S0301With CONSULT-II
Selecting ªSRT STATUSº in ªDTC CONFIRMATIONº mode with CONSULT-II.
For items whose SRT codes are set, a ªCMPLTº is displayed on the CONSULT-II screen; for items whose SRT
codes are not set, ªINCMPº is displayed.
With GST
Selecting Mode 1 with GST (Generic Scan Tool)
A sample of CONSULT-II display for SRT code is shown below.
ªINCMPº means the self-diagnosis is incomplete and SRT is not set. ªCMPLTº means the self-diagnosis is
complete and SRT is set.
ON BOARD DIAGNOSTIC SYSTEM DESCRIPTION
Emission-related Diagnostic Information (Cont'd)
EC-64

SEF949Z
How to Set SRT CodeNBEC0031S0302To set all SRT codes, self-diagnosis for the items indicated above must be performed one or more times. Each
diagnosis may require a long period of actual driving under various conditions.
With CONSULT-II
Perform corresponding DTC Confirmation Procedure one by one based on ªPerformance Priorityº in the table
on EC-62.
Without CONSULT-II
The most efficient driving pattern in which SRT codes can be properly set is explained on the next page. The
driving pattern should be performed one or more times to set all SRT codes.
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ON BOARD DIAGNOSTIC SYSTEM DESCRIPTION
Emission-related Diagnostic Information (Cont'd)
EC-65

Driving PatternNBEC0031S0303
SEF947Y
ON BOARD DIAGNOSTIC SYSTEM DESCRIPTION
Emission-related Diagnostic Information (Cont'd)
EC-66

IThe time required for each diagnosis varies with road surface conditions, weather, altitude, individual driv-
ing habits, etc.
Zone A refers to the range where the time required, for the diagnosis under normal conditions*, is the
shortest.
Zone B refers to the range where the diagnosis can still be performed if the diagnosis is not completed
within zone A.
*: Normal conditions refer to the following:
þ Sea level
þ Flat road
þ Ambient air temperature: 20 - 30ÉC (68 - 86ÉF)
þ Diagnosis is performed as quickly as possible under normal conditions.
Under different conditions [For example: ambient air temperature other than 20 - 30ÉC (68 - 86ÉF)], diag-
nosis may also be performed.
Pattern 1:
IThe engine is started at the engine coolant temperature of þ10 to 35ÉC (14 to 95ÉF)
(where the voltage between the ECM terminal 70 and ground is 3.0 - 4.3V).
IThe engine must be operated at idle speed until the engine coolant temperature is greater than 70ÉC
(158ÉF) (where the voltage between the ECM terminal 70 and ground is lower than 1.4V).
IThe engine is started at the fuel tank temperature of warmer than 0ÉC (32ÉF) (where the voltage
between the ECM terminal 92 and ground is less than 4.1V).
Pattern 2:
IWhen steady-state driving is performed again even after it is interrupted, each diagnosis can be conducted.
In this case, the time required for diagnosis may be extended.
Pattern 3:
IThe driving pattern outlined in *2 must be repeated at least 3 times.
Pattern 4:
ITests are performed after the engine has been operated for at least 17 minutes.
IThe accelerator pedal must be held very steady during steady-state driving.
IIf the accelerator pedal is moved, the test must be conducted all over again.
*1: Depress the accelerator pedal until vehicle speed is 90 km/h (56 MPH), then release the accelerator pedal
and keep it released for more than 10 seconds. Depress the accelerator pedal until vehicle speed is 90 km/h
(56 MPH) again.
*2: Operate the vehicle in the following driving pattern.
1) Decelerate vehicle to 0 km/h (0 MPH) and let engine idle.
2) Repeat driving pattern shown below at least 10 times.
IDuring acceleration, hold the accelerator pedal as steady as possible.
SEF414S
*3: Checking the vehicle speed with GST is advised.
Suggested Transmission Gear Position for A/T Models
Set the selector lever in the ªDº position with the overdrive switch turned ON.
Suggested upshift speeds for M/T models
Shown below are suggested vehicle speeds for shifting into a higher gear. These suggestions relate to fuel
economy and vehicle performance. Actual upshift speeds will vary according to road conditions, the weather
and individual driving habits.
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ON BOARD DIAGNOSTIC SYSTEM DESCRIPTION
Emission-related Diagnostic Information (Cont'd)
EC-67