2001 TOYOTA AVALON light
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- DIAGNOSTICSENGINE
DI-53
209 Author: Date:
DTC P0171 System too Lean (Fuel Trim)
DTC P0172 System too Rich (Fuel Trim)
DTC P0174 System too Lean (A/F Lean Malfunction,
Bank2)
DTC P0175 System too Rich (Bank2)
CIRCUIT DESCRIPTION
Fuel trim refers to the feedback compensation value compared to the basic injection time. 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 air-fuel ratio at its ideal
theoretical value.
The signal from the A/F sensor is approximately proportional to the existing air-fuel ratio, and ECM compar-
ing it with the ideal theoretical value, the ECM reduces fuel volume immediately if the air-fuel ratio is rich
and increases fuel volume if it is lean.
Long-term fuel trim compensates the deviation from the central value of the short-term fuel trim stored up
by each engine tolerance, and the deviation from the central value due to the passage of time and changes
of using environment.
If both the short-term fuel trim and long-term fuel trim exceed a certain value, it is detected as a malfunction
and the MIL lights up.
DTC No.DTC Detecting ConditionTrouble Area
P0171
P0174When air-fuel ratio feedback is stable after engine warming up,
fuel trim is considerably in error on rich side (2 trip detection
logic)
Air induction system
Injector blockage
Mass air flow meter
Engine coolant temp. sensor
Fuel pressure
Gas leakage on exhaust system
Open or short in A/F sensor (bank 1, 2 sensor 1) circuit
A/F sensor (bank 1, 2 sensor 1)
ECM
P0172
P0175When air-fuel ratio feedback is stable after engine warming up,
fuel trim is considerably in error on lean side (2 trip detection
logic)
Injector leak, blockage
Mass air flow meter
Engine coolant temp. sensor
Ignition system
Fuel pressure
Gas leakage on exhaust system
Open or short in A/F sensor (bank 1, 2 sensor 1) circuit
A/F sensor (bank 1, 2 sensor 1)
ECM
DI6T4-03
Page 1029 of 1897
DI079-04
ENGINE CONTROL SYSTEM Check Sheet
Customer's Name
Driver's Name
Date Vehicle
Brought in
License No.
Model and Model
Year
Frame No.
Engine Model
Odometer Reading
Problem Symptoms
Engine does
not Start
Difficult to
Start
Poor Idling
Poor
Driveability
Engine Stall
Others
Engine does not crankNo initial combustionNo complete combustion
Engine cranks slowly
Other
Incorrect first idleIdling rpm is abnormalHigh ( rpm)Low ( rpm)
Rough idling
Other
HesitationBack fireMuffler explosion (after-fire)Surging
Knocking
Other
Soon after startingAfter accelerator pedal depressed
After accelerator pedal released
During A/C operation
Shifting from N to D
Other
Dates Problem
Occurred
Problem Frequency
Condition When
Problem Occurs
Weather
Engine Operation
Engine Temperature Place Outdoor
TemperatureConstant
Sometimes ( times per day/month)Once only
Other
Fine
CloudyRainySnowyVarious/Other
Hot
Warm CoolCold (approx. °F/ °C)
Highway
SuburbsInner cityUphillDownhill
Rough road
Other
Cold
Warming upAfter warming upAny temperatureOther
Starting
Just after starting ( min.)IdlingRacing
Driving
Constant speedAccelerationDeceleration
A/C switch ON/OFF
Other
Condition of MILRemains on Sometimes light up Does not light up
NormalMalfunction code(s) (code )
Freezed frame data ( )
NormalMalfunction code(s) (code )
Freezed frame data ( )
Normal Mode
(Precheck)
Check Mode DTC InspectionInspector's
Name
km
miles
DI-2
- DIAGNOSTICSENGINE
158 Author: Date:
2001 AVALON (RM808U)
CUSTOMER PROBLEM ANALYSIS CHECK
Page 1032 of 1897
DI-16
- DIAGNOSTICSENGINE
172 Author: Date:
P0440
(DI-74)Evaporative Emission Control
System Malfunction
Hose or tube cracked, holed, damaged or insufficient seal
Fuel tank cap incorrectly installed
Fuel tank cap cracked or damaged
Vacuum hose cracked, holed, blocked, damaged or discon-
nected
Fuel tank cracked, holed or damaged
Charcoal canister cracked, holed or damaged
Open or short in vapor pressure sensor circuit
Vapor pressure sensor
Fuel tank over fill check valve cracked or damaged
ECM
P0441
(DI-80)Evaporative Emission Control
System Incorrect Purge Flow
Vacuum hose cracked, holed blocked, damaged or discon-
nected ((1), (2), (3), (4), (5), (6), (7), (8), (9), (10) and (11) in
Fig. 1)
Fuel tank cap incorrectly installed
Fuel tank cap cracked or damaged
Open or short in vapor pressure sensor circuit
Vapor pressure sensor
Open or short in VSV circuit for EVAP
VSV for EVAP
Open or short in VSV circuit for CCV
VSV for CCV
Open or short in VSV circuit for pressure switching valve
VSV for pressure switching valve
Fuel tank cracked, holed or damaged
Charcoal canister cracked, holed or damaged
Fuel tank over fill check valve cracked or damaged
ECM
P0442
(DI-74)Evaporative Emission Control
System Leak Detected (Small
Leak)
Same as DTC No. P0440
P0446
(DI-80)Evaporative Emission Control
System Vent Control MalfunctionSame as DTC No. P0441
P0450
(DI-97)Evaporative Emission Control
System Pressure Sensor Mal-
function
Open or short in vapor pressure sensor circuit
V
P0451
(DI-97)Evaporative Emission Control
System Pressure Sensor Range/
PerformanceVapor pressure sensor
ECM
P0500
(DI-99)Vehicle Speed Sensor Malfunc-
tionCombination meter
Open or short in speed sensor circuit
ECM
P0505
(DI-102)Idle Control System Malfunction
Open or short in IAC valve circuit
IAC valve is stuck or closed
Open or short in A/C signal circuit
Air induction system
ECM
*1: MIL lights up
*2: MIL light up or blinking
Page 1034 of 1897
DI-18
- DIAGNOSTICSENGINE
174 Author: Date:
P1335
(DI-123)Crankshaft Position Sensor Cir-
cuit Malfunction (During engine
running)Open or short in crankshaft position sensor circuit
Crankshaft position sensor
Camshaft timing gear
ECM
-
P1345
(DI-1 11)VVT Sensor/Camshaft position
Sensor Circuit Malfunction (Bank
1)Open or short in VVT sensor (camshaft position Sensor) circuit
VVT sensor (camshaft position Sensor)
ECM
P1346
(DI-126)VVT Sensor/Camshaft position
Sensor Circuit Range/Perfor-
mance Problem (Bank 1)Mechanical system (Jumping teeth of timing belt, belt
stretched)
ECM
P1349
(DI-127)VVT System Malfunction (Bank
1)
Valve timing
OCV
VVT controller assembly
ECM
P1350
(DI-124)VVT Sensor/Camshaft position
Sensor Circuit Malfunction (Bank
2)
Same as DTC No. P1345
P1351
(DI-126)VVT Sensor/Camshaft position
Sensor Circuit Range/Perfor-
mance Problem (Bank 2)
Same as DTC No. P1346
P1354
(DI-127)VVT System Malfunction (Bank
2)Same as DTC No. P1349
P1520
(DI-134)Stop Light Switch Signal Mal-
functionShort in stop light switch signal circuit
Stop light switch
ECM
P1600
(DI-136)ECM BATT MalfunctionOpen in back up power source circuit
ECM
P1656
(DI-138)OCV Circuit Malfunction (Bank
1)Open or short in OCV circuit
OCVP1663
(DI-138)OCV Circuit Malfunction (Bank
2)OCV
ECM
P1780
(DI-141)Park/Neutral Position Switch
MalfunctionShort in park/neutral position switch circuit
Park/neutral position switch
ECM
B2795
(DI-605)Unmatched Key CodeImmobiliser system-
B2796
(DI-606)No Communication in Immobilis-
er SystemImmobiliser system-
B2797
(DI-609)Communication Malfunction No.1Immobiliser system-
*: MIL lights up. - MIL does not light up.
Page 1037 of 1897
DI07A-09
S05349
A10838
TOYOTA Hand-Held tester
- DIAGNOSTICSENGINE
DI-3
159 Author: Date:
2001 AVALON (RM808U)
PRE-CHECK
1. DIAGNOSIS SYSTEM
(a) Description
When troubleshooting OBD II vehicles, the only dif-
ference from the usual troubleshooting procedure
is that you connect the vehicle to the OBD II scan
tool complying with SAE J1978 or TOYOTA hand-
held tester, and read off various data output from
the vehicle's ECM.
OBD II regulations require that the vehicle's on-
board computer lights up the Malfunction Indicator
Lamp (MIL) on the instrument panel when the com-
puter detects a malfunction in the emission control
system/components or in the powertrain control
components which affect vehicle emissions, or a
malfunction in the computer. In addition to the MIL
lighting up when a malfunction is detected, the ap-
plicable Diagnostic Trouble Codes (DTCs) pre-
scribed by SAE J2012 are recorded in the ECM
memory (See page DI-14).
If the malfunction does not reoccur in 3 consecutive trips, the
MIL goes off automatize but the DTC remain recorded in the
ECM memory.
To check the DTC, connect the OBD II scan tool or
TOYOTA hand-held tester to the Data Link Con-
nector 3 (DLC3) on the vehicle. The OBD II scan
tool or TOYOTA hand-held tester also enables you
to erase the DTC and check freezed frame data and
various forms of engine data (For operating instruc-
tions, see the OBD II scan tool's instruction book.).
DTC include SAE controlled codes and manufac-
turer controlled codes. SAE controlled codes must
be set as prescribed by the SAE, while manufactur-
er controlled codes can be set freely by the
manufacturer within the prescribed limits (See DTC
chart on page DI-14).
Page 1038 of 1897
DI-4
- DIAGNOSTICSENGINE
160 Author: Date:
2001 AVALON (RM808U)
The diagnosis system operates in normal mode
during normal vehicle use. It also has a check mode
for technicians to simulate malfunction symptoms
and troubleshoot. Most DTC use 2 trip detection
logic* to prevent erroneous detection, and ensure
thorough malfunction detection. By switching the
ECM to check mode when troubleshooting, the
technician can cause the MIL to light up for a mal-
function that is only detected once or momentarily
(TOYOTA hand-held tester only). (See step 2)
*2 trip detection logic:
When a malfunction is first detected, the malfunc-
tion is temporarily stored in the ECM memory. (1st
trip)
If the same malfunction is detected again during the second
drive test, this second detection causes the MIL to light up. (2nd
trip) the 2 trip repeats the same mode a 2nd time (However, the
ignition switch must be turned OFF between the 1st trip and 2nd
trip.).
Freeze frame data:
Freeze frame data records the engine condition
when a misfire (DTCs P0300 - P0306) or fuel trim
malfunction (DTCs P0171 and P0172) or other mal-
function (first malfunction only), is detected. Be-
cause freeze frame data records the engine condi-
tions (fuel system, calculated load, engine coolant
temperature, fuel trim, engine speed, vehicle
speed, etc.) when the malfunction is detected.
When troubleshooting, it is useful for determining
whether the vehicle was running or stopped, the en-
gine was warmed up or not, the air-fuel ratio was
lean or rich, etc. at the time of the malfunction.
Priorities for troubleshooting:
If troubleshooting priorities for multiple DTCs are given in the
applicable DTC chart, these should be followed.
If no instructions are given, troubleshoot DTCs according to the
following priorities.
(1) DTC other than fuel trim malfunction (DTCs P0171
and P0172), and misfire (DTCs P0300 - P0306).
(2) Fuel trim malfunction (DTCs P0171 and P0172).
(3) Misfire (DTCs P0300 - P0306).
Page 1039 of 1897
A04550
DLC3
1
234
56
7
8
9
10 11 12 13 1415
16
S05349
- DIAGNOSTICSENGINE
DI-5
161 Author: Date:
2001 AVALON (RM808U)
(b) Check the DLC3.
The vehicle's ECM uses ISO 9141-2 for communication.
The terminal arrangement of DLC3 complies with SAE
J1962 and matches the ISO 9141-2 format.
Terminal No.Connection/Voltage or ResistanceCondition
7Bus Line/Pulse generationDuring transmission
4Chassis Ground e Body Ground/1 W or lessAlways
5Signal Ground e Body Ground/1 W or lessAlways
16Battery Positive e Body Ground/9 - 14 VAlways
HINT:
If your display shows UNABLE TO CONNECT TO VEHICLE
when you have connected the cable of the OBD II scan tool or
TOYOTA hand-held tester to the DLC3, turned the ignition
switch ON and operated the scan tool, there is a problem on the
vehicle side or tool side.
If communication is normal when the tool is connected to
another vehicle, inspect the DLC3 on the original vehicle.
If communication is still not possible when the tool is con-
nected to another vehicle, the problem is probably in the
tool itself, so consult the Service Department listed in the
tool's instruction manual.
2. INSPECT DIAGNOSIS (Normal Mode)
(a) Check the MIL.
(1) The MIL comes on when the ignition switch is turned
ON and the engine is not running.
HINT:
If the MIL does not light up, troubleshoot the combination meter
(See page BE-53).
(2) When the engine started, the MIL should go off. If
the lamp remains on, the diagnosis system has de-
tected a malfunction or abnormality in the system.
(b) Check the DTC.
NOTICE:
If there is no DTC in the normal mode, check the 1st
trip DTC using Continuous Test Results function
(Mode 7 for SAE J1979) or the OBD II scan tool or TOY-
OTA hand-held tester.
Page 1040 of 1897
DI-6
- DIAGNOSTICSENGINE
162 Author: Date:
2001 AVALON (RM808U)
TOYOTA hand-held tester only:
When the diagnosis system is switched from the nor-
mal mode to the check mode, it erases all DTC and
freezed frame data recorded in the normal mode. So
before switching modes, always check the DTC and
freezed frame data, and note them down.
(1) Prepare the OBD II scan tool (complying with SAE
J 1978) or TOYOTA hand-held tester.
(2) Connect the OBD II scan tool or TOYOTA hand-
held tester to the DLC3 at the lower center of the
instrument panel.
(3) Turn the ignition switch ON and push the OBD II
scan tool or TOYOTA hand-held tester switch ON.
(4) Use the OBD II scan tool or TOYOTA hand-held
tester to check the DTC and freezed frame data and
note them down (For operating instructions, see the
OBD II scan tool's instruction book.).
If there is no DTC in the normal mode, check the 1st
trip DTC using Continuous Test Results function
(Mode 7 for SAE J1979) on the OBD II scan tool or
TOYOTA hand-held tester.
(5) See page DI-14 to confirm the details of the DTC.
NOTICE:
When simulating symptoms with an OBD II scan tool
(excluding TOYOTA hand-held tester) to check the
DTC, use the normal mode. For code on the DTC chart
subject to º2 trip detection logicº, perform the follow-
ing either action.
Turn the ignition switch OFF after the symptom is
simulated the 1st time. Then repeat the simulation
process again. When the problem has been simulated
twice, the MIL lights up and the DTCs are recorded in
the ECM.
Check the 1st trip DTC using Mode 7 (Continuous Test
Results) for SAE J1979.
(c) Clear the DTC.
The DTCs and freezed frame data will be erased by either
action.
Operating the OBD II scan tool (complying
with SAE J1978) or TOYOTA hand-held tes-
ter to erase the codes. (See the OBD II scan
tool's instruction book for operating instruc-
tions.)
Disconnecting the battery terminals or EFI
fuse.