2001 NISSAN ALMERA N16 Mass air flow sensor

Mixture Ratio Feedback Control (Closed loop control)NJEC0014S04
SEF336WA
The mixture ratio feedback system provides the best air-fuel mixture ratio for driveability and emission con-
trol. The three way catalyst can then better reduce CO, HC and NOx emissions. This system uses a heated
oxygen sensor 1 (front) in the exhaust manifold to monitor if the engine operation is rich or lean. The ECM
adjusts the injection pulse width according to the sensor voltage signal. For more information about the heated
oxygen sensor 1 (front), refer to EC-176. This maintains the mixture ratio within the range of stoichiometric
(ideal air-fuel mixture).
This stage is referred to as the closed loop control condition.
Heated oxygen sensor 2 (rear) is located downstream of the three way catalyst. Even if the switching char-
acteristics of the heated oxygen sensor 1 (front) shift, the air-fuel ratio is controlled to stoichiometric by the
signal from the heated oxygen sensor 2 (rear).
Open Loop ControlNJEC0014S05The open loop system condition refers to when the ECM detects any of the following conditions. Feedback
control stops in order to maintain stabilized fuel combustion.
+Deceleration and acceleration
+High-load, high-speed operation
+Malfunction of heated oxygen sensor 1 (front) or its circuit
+Insufficient activation of heated oxygen sensor 1 (front) at low engine coolant temperature
+High engine coolant temperature
+During warm-up
+When starting the engine
Mixture Ratio Self-learning ControlNJEC0014S06The mixture ratio feedback control system monitors the mixture ratio signal transmitted from the heated oxy-
gen sensor 1 (front). This feedback signal is then sent to the ECM. The ECM controls the basic mixture ratio
as close to the theoretical mixture ratio as possible. However, the basic mixture ratio is not necessarily con-
trolled as originally designed. Both manufacturing differences (i.e., mass air flow sensor hot film) and charac-
teristic changes during operation (i.e., injector clogging) directly affect mixture ratio.
Accordingly, the difference between the basic and theoretical mixture ratios is monitored in this system. This
is then computed in terms of ªinjection pulse durationº to automatically compensate for the difference between
the two ratios.
ªFuel trimº refers to the feedback compensation value compared against the basic injection duration. Fuel trim
includes short term fuel trim and long term fuel trim.
ªShort term fuel trimº is the short-term fuel compensation used to maintain the mixture ratio at its theoretical
value. The signal from the heated oxygen sensor 1 (front) indicates whether the mixture ratio is RICH or LEAN
compared to the theoretical value. The signal then triggers a reduction in fuel volume if the mixture ratio is
rich, and an increase in fuel volume if it is lean.
ªLong term fuel trimº is overall fuel compensation carried out long-term to compensate for continual deviation
of the short term fuel trim from the central value. Such deviation will occur due to individual engine differences,
wear over time and changes in the usage environment.
ENGINE AND EMISSION BASIC CONTROL SYSTEM DESCRIPTIONQG
Multiport Fuel Injection (MFI) System (Cont'd)
EC-30

Fuel Injection TimingNJEC0014S07
SEF337W
Two types of systems are used.
Sequential Multiport Fuel Injection System
NJEC0014S0701Fuel is injected into each cylinder during each engine cycle according to the firing order. This system is used
when the engine is running.
Simultaneous Multiport Fuel Injection System
NJEC0014S0702Fuel is injected simultaneously into all four cylinders twice each engine cycle. In other words, pulse signals of
the same width are simultaneously transmitted from the ECM.
The four injectors will then receive the signals two times for each engine cycle.
This system is used when the engine is being started and/or if the fail-safe system (CPU) is operating.
Fuel Shut-offNJEC0014S08Fuel to each cylinder is cut off during deceleration or operation of the engine at excessively high speeds.
Electronic Ignition (EI) System
DESCRIPTIONNJEC0015Input/Output Signal ChartNJEC0015S01
Sensor Input Signal to ECMECM func-
tionActuator
Crankshaft position sensor (POS) Engine speed
Ignition tim-
ing controlPower transistor Camshaft position sensor (PHASE) Engine speed and cylinder number
Mass air flow sensor Amount of intake air
Engine coolant temperature sensor Engine coolant temperature
Throttle position sensorThrottle position
Throttle valve idle position
Vehicle speed sensor Vehicle speed
Ignition switch Start signal
Knock sensor Engine knocking
PNP switch Gear position
Battery Battery voltage
ENGINE AND EMISSION BASIC CONTROL SYSTEM DESCRIPTIONQG
Multiport Fuel Injection (MFI) System (Cont'd)
EC-31

21 CHECK HEATED OXYGEN SENSOR 1 (FRONT) SIGNAL
With CONSULT-II
1. Stop engine.
2. Replace heated oxygen sensor 1 (front).
3. Start engine and warm it up to normal operating temperature.
4. Run engine at approx. 2,000 rpm for approx. 2 minutes under no-load.
5. See ªHO2S1 MNTR (B1)º in ªDATA MONITORº mode.
6. Running engine at 2,000 rpm under no-load (engine is warmed up to normal operating temperature.), check that the
monitor fluctuates between ªLEANº and ªRICHº more than 5 times during 10 seconds.
1 time: RICH®LEAN®RICH
2 times: RICH®LEAN®RICH®LEAN®RICH
Without CONSULT-II
1. Stop engine.
2. Replace heated oxygen sensor 1 (front).
3. Start engine and warm it up to normal operating temperature.
4. Run engine at approx. 2,000 rpm for approx. 2 minutes under no-load.
5. Set voltmeter probe between ECM terminal 62 and ground.
6. Make sure that the voltage fluctuates between 0 to 0.3V and 0.6 to 1.0V more than 5 times during 10 seconds at 2,000
rpm.
1 time: 0 - 0.3V®0.6 - 1.0V®0 - 0.3V
2 times: 0 - 0.3V®0.6 - 1.0V®0 - 0.3V®0.6 - 1.0V®0 - 0.3V
OK or NG
OK©INSPECTION END
NG©GO TO 22.
22 DETECT MALFUNCTIONING PART
Check the following.
1. Check fuel pressure regulator. Refer to EC-39.
2. Check mass air flow sensor and its circuit. Refer to EC-152.
3. Check injector and its circuit. Refer to EC-446.
Clean or replace if necessary.
4. Check engine coolant temperature sensor and its circuit. Refer to EC-163.
5. Check ECM function by substituting another known-good ECM.
(ECM may be the cause of a problem, but this is rarely the case.)
©GO TO 3.
23 CHECK HEATED OXYGEN SENSOR 1 (FRONT) HARNESS
1. Turn off engine and disconnect battery ground cable.
2. Disconnect ECM harness connector.
3. Disconnect heated oxygen sensor 1 (front) harness connector.
4. Check harness continuity between ECM terminal 62 and heated oxygen sensor 1 (front) harness connector terminal 1.
Refer to Wiring Diagram, EC-176.
Continuity should exist.
OK or NG
OK©GO TO 25.
NG©GO TO 24.
24 REPAIR OR REPLACE
Repair or replace harness between ECM and heated oxygen sensor 1 (front).
©GO TO 3.
BASIC SERVICE PROCEDUREQG
Inspection Procedure (Cont'd)
EC-51

27 CHECK HEATED OXYGEN SENSOR 1 (FRONT) SIGNAL
With CONSULT-II
1. Stop engine.
2. Replace heated oxygen sensor 1 (front).
3. Start engine and warm it up to normal operating temperature.
4. Run engine at approx. 2,000 rpm for approx. 2 minutes under no-load.
5. See ªHO2S1 MNTR (B1)º in ªDATA MONITORº mode.
6. Maintaining engine at 2,000 rpm under no-load (engine is warmed up to normal operating temperature.), check that the
monitor fluctuates between ªLEANº and ªRICHº more than 5 times during 10 seconds.
1 time: RICH®LEAN®RICH
2 times: RICH®LEAN®RICH®LEAN®RICH
Without CONSULT-II
1. Stop engine.
2. Replace heated oxygen sensor 1 (front).
3. Start engine and warm it up to normal operating temperature.
4. Run engine at approx. 2,000 rpm for approx. 2 minutes under no-load.
5. Set voltmeter probe between ECM terminal 62 and ground.
6. Make sure that voltage fluctuates between 0 - 0.3V and 0.6 - 1.0V more than 5 times during 10 seconds at 2,000 rpm.
1 time: 0 - 0.3V®0.6 - 1.0V®0 - 0.3V
2 times: 0 - 0.3V®0.6 - 1.0V®0 - 0.3V®0.6 - 1.0V®0 - 0.3V
OK or NG
OK©GO TO 3.
NG©GO TO 28.
28 DETECT MALFUNCTIONING PART
Check the following.
+Connect heated oxygen sensor 1 (front) harness connectors to heated oxygen sensors 1 (front).
+Check fuel pressure regulator. Refer to EC-39.
+Check mass air flow sensor and its circuit. Refer to EC-152.
+Check injector and its circuit. Refer to EC-446.
Clean or replace if necessary.
+Check engine coolant temperature sensor and its circuit. Refer to EC-163.
+Check ECM function by substituting another known-good ECM.
(ECM may be the cause of a problem, but this is rarely the case.)
©GO TO 3.
BASIC SERVICE PROCEDUREQG
Inspection Procedure (Cont'd)
EC-54

ENGINE CONTROL COMPONENT PARTS/CONTROL
SYSTEMS APPLICATION
NJEC0034S02
ItemDIAGNOSTIC TEST MODE
WORK
SUP-
PORTSELF-DIAGNOSTIC
RESULTS
D ATA
MONI-
TORD ATA
MONI-
TOR
(SPEC)ACTIVE
TESTDTC & SRT
CONFIRMATION
DTC*1FREEZE
FRAME
DATA*2SRT
STA-
TUSDTC
WORK
SUP-
PORT
ENGINE CONTROL COMPONENT PARTS
INPUTCamshaft position sensor
(PHASE)XEngine
speed
XEngine
speed
XEngine
speed
X
Crankshaft position sensor
(POS)X*3
Mass air flow sensor X X X
Engine coolant temperature
sensorXXXXX
Heated oxygen sensor 1
(front)X X X X*3 X*3
Heated oxygen sensor 2
(rear)X*3 X X X*3 X*3
Vehicle speed sensorXXXX
Throttle position sensor X X X
EGR temperature sensor*4 X*3 X X
Intake air temperature sensor X*3 X X X
Knock sensor X
Ignition switch (start signal) X X
Closed throttle position
switch*4X*3 X X
Closed throttle position switch
(throttle position sensor sig-
nal)XX
Air conditioner switch X X
Refrigerant pressure sensor X X
Park/Neutral position (PNP)
switchX*3 X X
Power steering oil pressure
switchXX
Electrical load X X
Heater fan switch X X
Battery voltage X X
ON BOARD DIAGNOSTIC SYSTEM DESCRIPTIONQG
CONSULT-II (Cont'd)
EC-82

Freeze frame data
item*Description
ENGINE SPEED
[rpm]+The engine speed at the moment a malfunction is detected is displayed.
VEHICL SPEED
[km/h] or [mph]+The vehicle speed at the moment a malfunction is detected is displayed.
ABSOL TH´P/S [%]+The throttle valve opening angle at the moment a malfunction is detected is displayed.
B/FUEL SCHDL
[msec]+The base fuel schedule at the moment a malfunction is detected is displayed.
INT/A TEMP SE [ÉC]
or [ÉF]+The intake air temperature at the moment a malfunction is detected is displayed.
*: The items are the same as those of 1st trip freeze frame data.
DATA MONITOR MODENJEC0034S06
Monitored item [Unit]ECM
input
signalsMain
signalsDescription Remarks
ENG SPEED [rpm]jj+Indicates the engine speed computed from
the POS signal of the crankshaft position
sensor.+Accuracy becomes poor if engine
speed drops below the idle rpm.
+If the signal is interrupted while the
engine is running, an abnormal
value may be indicated.
MAS A/F SE-B1 [V]jj+The signal voltage of the mass air flow sen-
sor is displayed.+When the engine is stopped, a cer-
tain value is indicated.
B/FUEL SCHDL
[msec]+ªBase fuel scheduleº indicates the fuel
injection pulse width programmed into
ECM, prior to any learned on board correc-
tion.
A/F ALPHA-B1 [%]j+Indicates the mean value of the air-fuel
ratio feedback correction factor per cycle.+When the engine is stopped, a cer-
tain value is indicated.
+This data also includes the data for
the air-fuel ratio learning control.
COOLAN TEMP/S
[ÉC] or [ÉF]jj+The engine coolant temperature (deter-
mined by the signal voltage of the engine
coolant temperature sensor) is displayed.+When the engine coolant tempera-
ture sensor is open or short-
circuited, ECM enters fail-safe
mode. The engine coolant tempera-
ture determined by the ECM is dis-
played.
HO2S1 (B1) [V]jj+The signal voltage of the heated oxygen
sensor 1 (front) is displayed.
HO2S2 (B1) [V]j+The signal voltage of the heated oxygen
sensor 2 (rear) is displayed.
HO2S1 MNTR (B1)
[RICH/LEAN]j+Display of heated oxygen sensor 1 (front)
signal during air-fuel ratio feedback control:
RICH ... means the mixture became ªrichº,
and control is being affected toward a
leaner mixture.
LEAN ... means the mixture became ªleanº,
and control is being affected toward a rich
mixture.+After turning ON the ignition switch,
ªRICHº is displayed until air-fuel
mixture ratio feedback control
begins.
+When the air-fuel ratio feedback is
clamped, the value just before the
clamping is displayed continuously.
ON BOARD DIAGNOSTIC SYSTEM DESCRIPTIONQG
CONSULT-II (Cont'd)
EC-85

Monitored item [Unit]ECM
input
signalsMain
signalsDescription Remarks
IGN TIMING [BTDC]j+Indicates the ignition timing computed by
ECM according to the input signals.
CAL/LD VALUE [%]+ªCalculated load valueº indicates the value
of the current airflow divided by peak air-
flow.
ABSOL TH.P/S [%]+ªAbsolute throttle position sensorº indicates
the throttle opening computed by ECM
according to the signal voltage of the
throttle position sensor.
MASS AIRFLOW
[gm/s]+Indicates the mass airflow computed by
ECM according to the signal voltage of the
mass air flow sensor.
IACV-AAC/V [step]j+Indicates the IACV-AAC valve control value
computed by ECM according to the input
signals.
PURG VOL C/V [%]+Indicates the EVAP canister purge volume
control solenoid valve computed by the
ECM according to the inpuct signals.
+The opening becomes larger as the value
increases.
EGR VOL CON/V
[step]*j+Indicates the EGR volume control valve
computed by the ECM according to the
input signals.
+The opening becomes larger as the value
increases.
INT/V SOL-B1
[ON/OFF]+The control condition of the valve timing
solenoid valve (determined by ECM accord-
ing to the input signal) is indicated.
ON ... Intake valve timing control operating
OFF ... Intake valve timing control not oper-
ating
AIR COND RLY
[ON/OFF]j+Indicates the air conditioner relay control
condition determined by ECM according to
the input signals.
FUEL PUMP RLY
[ON/OFF]j+Indicates the fuel pump relay control condi-
tion determined by ECM according to the
input signals.
COOLING FAN
[ON/OFF]j+Indicates [ON/OFF] control condition of the
cooling fan determined by ECM according
to the input signals.
HO2S1 HTR (B1)
[ON/OFF]+Indicates [ON/OFF] condition of heated oxy-
gen sensor 1 heater (front) determined by
ECM according to the input signals.
HO2S2 HTR (B1)
[ON/OFF]+Indicates [ON/OFF] condition of heated oxy-
gen sensor 2 heater (rear) determined by
ECM according to the input signals.
ON BOARD DIAGNOSTIC SYSTEM DESCRIPTIONQG
CONSULT-II (Cont'd)
EC-87

Monitored item [Unit]ECM
input
signalsMain
signalsDescription Remarks
IDL A/V LEARN+Display the condition of idle air volume
learning
YET ... Idle air volume learning has not
been performed yet.
CMPLT ... Idle air volume learning has
already been performed successfully.
INCMP ... Idle air volume learning has not
been performed successfully.
TRVL AFTER MIL
[km] or [Mile]+Distance traveled while MI is activated
VOLTAGE [V]+Voltage measured by the voltage probe.
PULSE
[msec] or [Hz] or [%]+Pulse width, frequency or duty cycle mea-
sured by the pulse probe.+Only ª#º is displayed if item is
unable to be measured.
+Figures with ª#ºs are temporary
ones. They are the same figures as
an actual piece of data which was
just previously measured.
*: If so equipped
NOTE:
Any monitored item that does not match the vehicle being diagnosed is deleted from the display automatically.
DATA MONITOR (SPEC) MODENJEC0034S11
Monitored item [Unit]ECM
input
signalsMain
signalsDescription Remarks
MAS A/F SE-B1 [V]jj+The signal voltage of the mass air flow sen-
sor specification is displayed.+When the engine is running, speci-
fication range is indicated.
B/FUEL SCHDL
[msec]+ªBase fuel scheduleº indicates the fuel
injection pulse width programmed into
ECM, prior to any learned on board correc-
tion.+When the engine is running, speci-
fication range is indicated.
A/F ALPHA-B1 [%]j+Indicates the mean value of the air-fuel
ratio feedback correction factor per cycle.+When the engine is running, speci-
fication range is indicated.
+This data also includes the data for
the air-fuel ratio learning control.
NOTE:
Any monitored item that does not match the vehicle being diagnosed is deleted from the display automatically.
ACTIVE TEST MODENJEC0034S07
TEST ITEM CONDITION JUDGEMENT CHECK ITEM (REMEDY)
FUEL INJECTION+Engine: Return to the original
trouble condition
+Change the amount of fuel injec-
tion using CONSULT-II.If trouble symptom disappears, see
CHECK ITEM.+Harness and connector
+Fuel injectors
+Heated oxygen sensor 1 (front)
IGNITION TIMING+Engine: Return to the original
trouble condition
+Timing light: Set
+Retard the ignition timing using
CONSULT-II.If trouble symptom disappears, see
CHECK ITEM.+ªIdle Air Volume Leaningº (Refer
to EC-55.)
+Camshaft position sensor
(PHASE)
+Crankshaft position sensor
(POS)
+Engine component parts and
installing conditions
ON BOARD DIAGNOSTIC SYSTEM DESCRIPTIONQG
CONSULT-II (Cont'd)
EC-88