coolant INFINITI FX35 2007 Workshop Manual

COMBINATION METERS DI-17
C
D E
F
G H
I
J
L
M A
B
DI
Revision: 2006 July 2007 FX35/FX45
PRELIMINARY CHECK
1. CHECK OPERATION OF SELF-DIAGNOSIS MODE (COMBINATION METER)
Perform self-diagnosis mode of combination meter. Refer to DI-15, "
OPERATION PROCEDURE" .
Does self-diagnosis function operate?
YES >> GO TO 2.
NO >> GO TO 3.
2. CHECK UNIFIED METER AND A/C AMP. (CONSULT-II)
Perform self-diagnosis of unified meter and A/C amp. Refer to DI-31, "
CONSULT-II Function (METER A/C
AMP)" .
Self-diagnosis results
No malfunction detected >> INSPECTION END
Malfunction detected >> Check applicable parts, and repair or replace corresponding parts.
3. CHECK POWER SUPPLY AND GROUND CIRCUIT OF COMBINATION METER
Check power supply and ground circuit of combination meter. Refer to DI-18, "
Power Supply and Ground Cir-
cuit Inspection" .
OK or NG
OK >> Check odo/trip meter switch. Refer to DI-24, "Odo/Trip Meter and Illumination Control Switch
Inspection" .
NG >> Repair malfunctioning part.
Symptom Chart NKS002ZM
Symptom Possible cause
Speedometer and odo/trip meter indication is malfunctioning. Refer to DI-19, "
Vehicle Speed Signal Inspection" .
Tachometer indication is malfunctioning. Refer to DI-20, "
Engine Speed Signal Inspection" .
Water temperature gauge indication is malfunctioning. Refer to DI-21, "
Engine Coolant Temperature Signal Inspection" .
Fuel gauge indication is malfunctioning. Refer to DI-21, "
Fuel Level Sensor Signal Inspection" .
Low-fuel warning lamp indication is irregular.
Shift position indicator is malfunctioning. Refer to DI-55, "
A/T Indicator Is Malfunction" .
Illumination control does not operate. Refer to
DI-24, "
Odo/Trip Meter and Illumination Control Switch
Inspection" .

COMBINATION METERS DI-21
C
D E
F
G H
I
J
L
M A
B
DI
Revision: 2006 July 2007 FX35/FX45
Engine Coolant Temperature Signal InspectionNKS002ZR
Symptom: Water temperature gauge indication is malfunction.
1. CHECK COMBINATION METER INPUT SIGNAL
1. Connect CONSULT-II, and start engine.
2. Select “METER A/C AMP” on CONSULT-II.
3. Using “W TEMP METER” on “DATA MONITOR”, compare the value of “DATA MONITOR” with water temperature gauge
pointer of combination meter.
OK or NG
OK >> GO TO 2.
NG >> Replace combination meter.
2. CHECK UNIFIED METER AND A/C AMP. INPUT SIGNAL
1. Select “ENGINE” on CONSULT-II.
2. Using “COOLAN TEMP/S” on “DATA MONITOR”, print out the CONSULT-II screen.
3. Select “METER A/C AMP” on CONSULT-II.
4. Using “W TEMP METER” on “DATA MONITOR”, compare the value of “DATA MONITOR” with that of the “COOLAN TEMP/S”.
OK or NG
OK >> Perform ECM self-diagnosis. Refer to EC-118, "CON-
SULT-II Function (ENGINE)" (VQ35DE) or EC-781,
"CONSULT-II Function (ENGINE)" (VK45DE).
NG >> Replace unified meter and A/C amp. Refer to DI-37,
"Removal and Installation of Unified Meter and A/C
Amp." .
Fuel Level Sensor Signal InspectionNKS002ZS
Symptom:

Fuel gauge indication is malfunctioning.

Low-fuel warning lamp indication is irregular.
NOTE:
The following symptoms are not malfunctions.
Fuel gauge

Depending on vehicle posture or driving circumstance, the fuel level in the tank varies, and the pointer
may fluctuate.

If the vehicle is fueled with the ignition switch ON, the pointer will move slowly.
Low-fuel warning lamp

Depending on vehicle posture or driving circumstance, the fuel in the tank flows and the warning lamp ON
timing may change.
Water temperature gauge pointer Reference value of data monitor [ °C ( °F)]
Hot Approx. 130 (266)
Middle Approx. 70 - 105 (158 - 221) Cold Approx. 50 (122)
PKIA2091E
SKIA4368E

DI-28
UNIFIED METER AND A/C AMP
Revision: 2006 July 2007 FX35/FX45
UNIFIED METER AND A/C AMPPFP:27760
System DescriptionNKS00300

For the unified meter and A/C amp., the signal required for controlling the combination meter are inte-
grated in the A/C auto amp.

The unified meter and A/C amp. corresponds to a CONSULT-II function (self-diagnosis results, CAN diag-
nosis support monitor, data monitor).
COMBINATION METER CONTROL FUNCTION

Unified meter and A/C amp. receives necessary information for combination meter from each unit by CAN
communication.

Unified meter and A/C amp. transmits a signals with communication line (TX, RX) between unified meter
and A/C amp. and combination meter.
Input/output signals between unified meter and A/C amp. and combination meter.
NOTE:
Combination meter performs fail-safe operation when unified meter and A/C amp. communication is malfunctioning. Refer to DI-8,
"FAIL-SAFE" . Unit Input Output
Unified meter and A/C amp.

Seat belt buckle switch signal (Driver's side)

Parking brake signal

Illumination control nighttime required signal

Refuel status signal

Low-fuel warning lamp condition signal

Combination meter receive error signal

Delivery destination data signal

Combination meter specifications signal

Vehicle speed signal (8-pulse)

Engine speed signal

Engine coolant temperature signal

Fuel level sensor signal (resistance value)

Malfunction indicator lamp signal

ABS warning lamp signal

Low tire pressure warning lamp signal

Run-flat tire warning lamp signal

Brake warning lamp signal

A/T CHECK warning lamp signal

ICC warning lamp signal

Oil pressure switch signal

Door switch signal

AWD warning lamp signal

Key warning lamp signal

VDC OFF indicator lamp signal

SLIP indicator lamp signal

CRUISE indicator lamp signal

SET indicator lamp signal

High beam request signal

Turn indicator signal

Snow mode switch signal

ICC system display signal

Shift position indicator signal

Manual mode indicator signal

Manual mode gear position signal

CAN communication condition signal of A/T

Position lights request signal

Buzzer output signal

DI-32
UNIFIED METER AND A/C AMP
Revision: 2006 July 2007 FX35/FX45
DATA MONITOR
Operation Procedure
1. Touch “DATA MONITOR” on “SELECT DIAG MODE” screen.
2. Touch either “MAIN SIGNALS” or “SELECTION FROM MENU” on the “DATA MONITOR” screen.
3. When “SELECTION FROM MENU” is selected, touch individual items to be monitored. When “MAIN SIG- NALS” is selected, main items will be monitored.
4. Touch “START”.
5. Touch “RECORD” while monitoring, then the status of the moni- tored item can be recorded. To stop recording, touch “STOP”.
Display Item List
X: Applicable
MAIN SIGNALS Monitors main signals.
SELECTION FROM MENU Selects and monitors individual signal.
SKIA4957E
Display item [Unit] MAIN
SIGNALS SELECTION
FROM MENU Contents
SPEED METER [km/h] or [mph] X X Displays the value of vehicle speed signal, which is input from
ABS actuator and electric unit (control unit).
SPEED OUTPUT [km/h] or [mph] X X Displays the value of vehicle speed signal, which is transmitted
to each unit with CAN communication.
TACHO METER [rpm] X X Displays the value of engine speed signal, which is input from
ECM.
W TEMP METER [ °C] or [ °F] X X Displays the value of engine coolant temperature signal, which
is input from ECM.
FUEL METER [lit.] X X Displays the value, which processes a resistance signal from
fuel gauge.
DISTANCE [km] or [mile] X X Displays the value, which is calculated by vehicle speed signal
from ABS actuator and electric unit (control unit), fuel gauge and
fuel consumption from ECM.
FUEL W/L [ON/OFF] X X Indicates [ON/OFF] condition of low-fuel warning lamp.
MIL [ON/OFF] X Indicates [ON/OFF] condition of malfunction indicator lamp.
AIR PRES W/L [ON/OFF] X Indicates [ON/OFF] condition of low tire pressure warning lamp.
SEAT BELT W/L [ON/OFF]
*1X Indicates [ON/OFF] condition of seat belt warning lamp.
BUZZER [ON/OFF] X X Indicates [ON/OFF] condition of buzzer.
DOOR W/L [ON/OFF] X Indicates [ON/OFF] condition of door warning lamp.
HI-BEAM IND [ON/OFF] X Indicates [ON/OFF] condition of high beam indicator.
TURN IND [ON/OFF] X Indicates [ON/OFF] condition of turn indicator.
OIL W/L [ON/OFF] X Indicates [ON/OFF] condition of oil pressure warning lamp.
VDC/TCS IND [ON/OFF] X Indicates [ON/OFF] condition of VDC OFF indicator lamp.
ABS W/L [ON/OFF] X Indicates [ON/OFF] condition of ABS warning lamp.
SLIP IND [ON/OFF] X Indicates [ON/OFF] condition of SLIP indicator lamp.
BRAKE W/L [ON/OFF]
*2X Indicates [ON/OFF] condition of brake warning lamp.
KEY G W/L [ON/OFF] X Indicates [ON/OFF] condition of key warning lamp (green).

DI-80
LANE DEPARTURE WARNING SYSTEM
Revision: 2006 July 2007 FX35/FX45
Action TestNKS00314
LDW SYSTEM RUNNING TEST
WARNING:

Be careful when performing road test.

Understand “Precautions” and “System Description” well before the road test. Refer to DI-77,
"Precautions for Lane Departure Warning (LDW) system" and DI-77, "System Description" .
Function Check
Check the LDW system operation according to the condition that the warning function works. Refer to DI-77,
"LDW SYSTEM OPERATION" .
Camera Aiming AdjustmentNKS00315
OUTLINE
Adjust the camera aiming every time the LDW camera unit is removed or installed.
CAUTION:

Place the vehicle on the level ground when the camera aiming adjustment is operated.

Follow the CONSULT-II when adjusting the camera aiming. (Camera aiming adjustment cannot be
operated without CONSULT-II.)
PREPARATION

Keep all tires inflated to correct pressures. Adjust the tire pressure to the specified pressure value.

There is no-load in vehicle. Check if coolant, engine oil are filled up to correct level and fuel tank is full.

Shift the gear into “P” position and release the parking brake.

Clean the windshield.
NOTE:
Do not place anything reflective on the upper surface of instrument panel.
TARGET SETTING
Preparation Aiming Adjustment Jig
For aiming adjustment, prepare the following jigs and targets.
PKIB4693E

EC-7
C
D E
F
G H
I
J
K L
M
EC A
Revision: 2006 July 2007 FX35/FX45
Wiring Diagram ...................................................
. 585
Diagnostic Procedure .......................................... . 586
Component Inspection ........................................ . 589
Removal and Installation ..................................... . 589
DTC P2135 TP SENSOR ....................................... . 590
Component Description ....................................... . 590
CONSULT-II Reference Value in Data Monitor Mode . 590
On Board Diagnosis Logic .................................. . 590
DTC Confirmation Procedure .............................. . 591
Wiring Diagram ................................................... . 592
Diagnostic Procedure .......................................... . 593
Component Inspection ........................................ . 596
Removal and Installation ..................................... . 596
DTC P2138 APP SENSOR .................................... . 597
Component Description ....................................... . 597
CONSULT-II Reference Value in Data Monitor Mode . 597
On Board Diagnosis Logic .................................. . 597
DTC Confirmation Procedure .............................. . 598
Wiring Diagram ................................................... . 599
Diagnostic Procedure .......................................... . 600
Component Inspection ........................................ . 604
Removal and Installation ..................................... . 604
DTC P2A00, P2A03 A/F SENSOR 1 ..................... . 605
Component Description ....................................... . 605
CONSULT-II Reference Value in Data Monitor Mode . 605
On Board Diagnosis Logic .................................. . 605
DTC Confirmation Procedure .............................. . 606
Wiring Diagram ................................................... . 607
Diagnostic Procedure .......................................... . 610
Removal and Installation ..................................... . 616
ASCD BRAKE SWITCH ........................................ . 617
Component Description ....................................... . 617
CONSULT-II Reference Value in Data Monitor Mode . 617
Wiring Diagram ................................................... . 618
Diagnostic Procedure .......................................... . 619
Component Inspection ........................................ . 623
ASCD INDICATOR ................................................ . 624
Component Description ....................................... . 624
CONSULT-II Reference Value in Data Monitor Mode . 624
Wiring Diagram ................................................... . 625
Diagnostic Procedure .......................................... . 626
ELECTRICAL LOAD SIGNAL ............................... . 627
Description .......................................................... . 627
CONSULT-II Reference Value in Data Monitor Mode . 627
Diagnostic Procedure .......................................... . 627
FUEL INJECTOR ................................................... . 629
Component Description ....................................... . 629
CONSULT-II Reference Value in Data Monitor Mode . 629
Wiring Diagram ................................................... . 630
Diagnostic Procedure .......................................... . 631
Component Inspection ........................................ . 635
Removal and Installation ..................................... . 635 FUEL PUMP ...........................................................
.636
Description ........................................................... .636
CONSULT-II Reference Value in Data Monitor Mode .636
Wiring Diagram .................................................... .637
Diagnostic Procedure .......................................... .638
Component Inspection ......................................... .641
Removal and Installation ..................................... .641
ICC BRAKE SWITCH ............................................ .642
Component Description ....................................... .642
CONSULT-II Reference Value in Data Monitor Mode .642
Wiring Diagram .................................................... .643
Diagnostic Procedure .......................................... .644
Component Inspection ......................................... .649
IGNITION SIGNAL ................................................. .650
Component Description ....................................... .650
Wiring Diagram .................................................... .651
Diagnostic Procedure .......................................... .656
Component Inspection ......................................... .661
Removal and Installation ..................................... .662
REFRIGERANT PRESSURE SENSOR ................. .663
Component Description ....................................... .663
Wiring Diagram .................................................... .664
Diagnostic Procedure .......................................... .665
Removal and Installation ..................................... .667
SNOW MODE SWITCH ......................................... .668
Description ........................................................... .668
CONSULT-II Reference Value in the Data Monitor
Mode .................................................................... .668
Wiring Diagram .................................................... .669
Diagnostic Procedure .......................................... .670
Component Inspection ......................................... .672
MIL AND DATA LINK CONNECTOR ..................... .673
Wiring Diagram .................................................... .673
SERVICE DATA AND SPECIFICATIONS (SDS) ... .675
Fuel Pressure ...................................................... .675
Idle Speed and Ignition Timing ............................ .675
Calculated Load Value ......................................... .675
Mass Air Flow Sensor .......................................... .675
Intake Air Temperature Sensor ............................ .675
Engine Coolant Temperature Sensor .................. .675
Air Fuel Ratio (A/F) Sensor 1 Heater ................... .675
Heated Oxygen sensor 2 Heater ......................... .675
Crankshaft Position Sensor (POS) ...................... .675
Camshaft Position Sensor (PHASE) ................... .675
Throttle Control Motor .......................................... .675
Fuel Injector ......................................................... .676
Fuel Pump ........................................................... .676
VK45DE
INDEX FOR DTC .................................................... .677
DTC No. Index ..................................................... .677
Alphabetical Index ............................................... .681
PRECAUTIONS ..................................................... .685
Precautions for Supplemental Restraint System
(SRS) “AIR BAG” and “SEAT BELT PRE-TEN-
SIONER” .............................................................. .685

EC-14Revision: 2006 July 2007 FX35/FX45
Component Inspection .........................................
1286
Removal and Installation ..................................... 1286
DTC P2A00, P2A03 A/F SENSOR 1 ..................... 1287
Component Description ....................................... 1287
CONSULT-II Reference Value in Data Monitor Mode 1287
On Board Diagnosis Logic ................................... 1287
DTC Confirmation Procedure .............................. 1288
Wiring Diagram .................................................... 1289
Diagnostic Procedure .......................................... 1292
Removal and Installation ..................................... 1298
ASCD BRAKE SWITCH ......................................... 1299
Component Description ....................................... 1299
CONSULT-II Reference Value in Data Monitor Mode 1299
Wiring Diagram .................................................... 1300
Diagnostic Procedure .......................................... 1301
Component Inspection ......................................... 1305
ASCD INDICATOR ................................................. 1306
Component Description ....................................... 1306
CONSULT-II Reference Value in Data Monitor Mode 1306
Wiring Diagram .................................................... 1307
Diagnostic Procedure .......................................... 1308
ELECTRICAL LOAD SIGNAL ............................... 1309
Description ........................................................... 1309
CONSULT-II Reference Value in Data Monitor Mode 1309
Diagnostic Procedure .......................................... 1309
FUEL INJECTOR ................................................... 1311
Component Description ....................................... 1311
CONSULT-II Reference Value in Data Monitor Mode
1311
Wiring Diagram .................................................... 1312
Diagnostic Procedure .......................................... 1313
Component Inspection ......................................... 1317
Removal and Installation ..................................... 1317
FUEL PUMP ........................................................... 1318
Description ........................................................... 1318
CONSULT-II Reference Value in Data Monitor Mode 1318
Wiring Diagram .................................................... 1319
Diagnostic Procedure .......................................... 1320
Component Inspection ......................................... 1323
Removal and Installation ..................................... 1323
ICC BRAKE SWITCH ............................................. 1324
Component Description ....................................... 1324
CONSULT-II Reference Value in Data Monitor Mode 1324
Wiring Diagram .................................................... 1325
Diagnostic Procedure ........................................... 1326
Component Inspection ......................................... 1331
IGNITION SIGNAL ................................................. 1332
Component Description ....................................... 1332
Wiring Diagram .................................................... 1333
Diagnostic Procedure ........................................... 1338
Component Inspection ......................................... 1343
Removal and Installation ...................................... 1344
REFRIGERANT PRESSURE SENSOR ................. 1345
Component Description ....................................... 1345
Wiring Diagram .................................................... 1346
Diagnostic Procedure ........................................... 1347
Removal and Installation ...................................... 1349
SNOW MODE SWITCH .......................................... 1350
Description ........................................................... 1350
CONSULT-II Reference Value in the Data Monitor
Mode .................................................................... 1350
Wiring Diagram .................................................... 1351
Diagnostic Procedure ........................................... 1352
Component Inspection ......................................... 1354
VARIABLE INDUCTION AIR CONTROL SYSTEM
(VIAS) ..................................................................... 1355
Description ........................................................... 1355
CONSULT-II Reference Value in Data Monitor Mode 1356
Wiring Diagram .................................................... 1357
Diagnostic Procedure ........................................... 1359
Component Inspection ......................................... 1362
Removal and Installation ...................................... 1363
MIL AND DATA LINK CONNECTOR ..................... 1364
Wiring Diagram .................................................... 1364
SERVICE DATA AND SPECIFICATIONS (SDS) ... 1366
Fuel Pressure ....................................................... 1366
Idle Speed and Ignition Timing ............................. 1366
Calculated Load Value ......................................... 1366
Mass Air Flow Sensor .......................................... 1366
Intake Air Temperature Sensor ............................ 1366
Engine Coolant Temperature Sensor ................... 1366
Fuel Tank Temperature Sensor ............................ 1366
Crankshaft Position Sensor (POS) ...................... 1366
Camshaft Position Sensor (PHASE) .................... 1366
A/F Sensor 1 Heater ............................................ 1366
Heated Oxygen sensor 2 Heater ......................... 1367
Throttle Control Motor .......................................... 1367
Fuel Injector ......................................................... 1367
Fuel Pump ............................................................ 1367

EC-28
[VQ35DE]
PREPARATION
Revision: 2006 July 2007 FX35/FX45
Commercial Service ToolsNBS003L0
Tool name
(Kent-Moore No.) Description
Leak detector
i.e.: (J-41416) Locating EVAP leak
EVAP service port
adapter
i.e.: (J-41413-OBD) Applying positive pressure through EVAP service
port
Fuel filler cap adapter
i.e.: (MLR-8382) Checking fuel tank vacuum relief valve opening
pressure
Socket wrench Removing and installing engine coolant temperature sensor
Oxygen sensor thread
cleaner
i.e.: (J-43897-18)
(J-43897-12) Reconditioning the exhaust system threads
before installing a new oxygen sensor. Use with
anti-seize lubricant shown below.
a: 18 mm diameter with pitch 1.5 mm for
Zirconia Oxygen Sensor
b: 12 mm diameter with pitch 1.25 mm for
Titania Oxygen Sensor
Anti-seize lubricant
i.e.: (Permatex
TM
133AR or equivalent
meeting MIL
specification MIL-A-
907) Lubricating oxygen sensor thread cleaning tool
when reconditioning exhaust system threads.
S-NT703
S-NT704
S-NT815
S-NT705
AEM488
S-NT779

EC-30
[VQ35DE]
ENGINE CONTROL SYSTEM
Revision: 2006 July 2007 FX35/FX45
Multiport Fuel Injection (MFI) SystemNBS003L2
INPUT/OUTPUT SIGNAL CHART
*1: This sensor is not used to control the engine system under normal conditions.
*2: This signal is sent to the ECM through CAN communication line.
*3: ECM determines the start signal status by the signals of engine speed and battery voltage.
SYSTEM DESCRIPTION
The amount of fuel injected from the fuel injector is determined by the ECM. The ECM controls the length of
time the valve remains open (injection pulse duration). The amount of fuel injected is a program value in the
ECM memory. The program value is preset by engine operating conditions. These conditions are determined
by input signals (for engine speed and intake air) from both the crankshaft position sensor and the mass air
flow sensor.
VARIOUS FUEL INJECTION INCREASE/DECREASE COMPENSATION
In addition, the amount of fuel injected is compensated to improve engine performance under various operat-
ing conditions as listed below.
<Fuel increase>

During warm-up

When starting the engine

During acceleration

Hot-engine operation

When selector lever is changed from N to D

High-load, high-speed operation
<Fuel decrease>

During deceleration

During high engine speed operation
Sensor Input Signal to ECM ECM function Actuator
Crankshaft position sensor (POS) Engine speed*
3
Piston position
Fuel injection
& mixture ratio
control Fuel injector
Camshaft position sensor (PHASE)
Mass air flow sensor Amount of intake air
Engine coolant temperature sensor Engine coolant temperature
Air fuel ratio (A/F) sensor 1 Density of oxygen in exhaust gas
Throttle position sensor Throttle position
Accelerator pedal position sensor Accelerator pedal position
Park/neutral position (PNP) switch Gear position
Knock sensor Engine knocking condition
Battery Battery voltage*
3
Power steering pressure sensor Power steering operation
Heated oxygen sensor 2*
1Density of oxygen in exhaust gas
Air conditioner switch Air conditioner operation*
2
Wheel sensorVehicle speed*2

ENGINE CONTROL SYSTEM EC-31
[VQ35DE]
C
D E
F
G H
I
J
K L
M A
EC
Revision: 2006 July 2007 FX35/FX45
MIXTURE RATIO FEEDBACK CONTROL (CLOSED LOOP CONTROL)
The mixture ratio feedback system provides the best air-fuel mixture ratio for driveability and emission control.
The three way catalyst 1 can then better reduce CO, HC and NOx emissions. This system uses air fuel ratio
(A/F) sensor 1 in the exhaust manifold to monitor whether the engine operation is rich or lean. The ECM
adjusts the injection pulse width according to the sensor voltage signal. For more information about air fuel
ratio (A/F) sensor 1, refer to EC-239, "
DTC P0131, P0151 A/F SENSOR 1" . 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 is located downstream of the three way catalyst 1. Even if the switching characteris-
tics of air fuel ratio (A/F) sensor 1 shift, the air-fuel ratio is controlled to stoichiometric by the signal from
heated oxygen sensor 2.
Open Loop Control
The 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 air fuel ratio (A/F) sensor 1 or its circuit

Insufficient activation of air fuel ratio (A/F) sensor 1 at low engine coolant temperature

High engine coolant temperature

During warm-up

After shifting from N to D

When starting the engine
MIXTURE RATIO SELF-LEARNING CONTROL
The mixture ratio feedback control system monitors the mixture ratio signal transmitted from air fuel ratio (A/F)
sensor 1. 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 controlled as orig-
inally designed. Both manufacturing differences (i.e., mass air flow sensor hot wire) and characteristic
changes during operation (i.e., fuel 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 “injection pulse duration” to automatically compensate for the difference between
the two ratios.
“Fuel trim” refers to the feedback compensation value compared against the basic injection duration. Fuel trim
includes short term fuel trim and long term fuel trim.
“Short term fuel trim” is the short-term fuel compensation used to maintain the mixture ratio at its theoretical
value. The signal from air fuel ratio (A/F) sensor 1 indicates whether the mixture ratio is RICH or LEAN com-
pared 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.
“Long term fuel trim” 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.
PBIB3020E