2001 TOYOTA AVALON air condition

A11416
Fusible
Link
Block
FL
Main
BatteryStop Light
Switch
ALT
B
F10
F6STOP
R
211D 1B
1E
45
Light
Failure
Sensor 7
2
To Stop LightE8 15ECM
STP
E1 Driver Side J/B
3 11
W
1 1
16
4C 3C
3164F3F 3
5IK1 1D 1
1GG-W
G-WDriver Side J/B
J/B No.3
J/B No.4
G-W
G-W G-W G-W
DI-134
- DIAGNOSTICSENGINE
290 Author
: Date
:
2001 AVALON (RM808U)
DTC P1520 Stop Light Switch Signal Malfunction
CIRCUIT DESCRIPTION
This signal is used to detect when the brakes have been applied. The STP signal voltage is the same as
the voltage supplied to the stop lights.
The STP signal is used mainly to control the fuel cut-off engine speed (The fuel cut-off engine speed is re-
duced slightly when the vehicle is braking.).
DTC No.DTC Detecting ConditionTrouble Area
P1520
Stop light switch does not turn off when repeating driving at 30
km or more 10 time or more after depressing brake (2 trip
detection logic)
Short in stop light switch signal circuit

Stop light switch

ECM
WIRING DIAGRAM
INSPECTION PROCEDURE
HINT:
Read freeze frame data using TOYOTA hand-held tester or OBD II scan tool. Because freeze frame records
the engine conditions when the malfunction is detected. When troubleshooting, it is useful for determining
whether the vehicle was running or stopped, the engine was warmed up or not, the air-fuel ratio was lean
or rich, etc. at the time of the malfunction.
1 Check operation of stop light.
CHECK:
Check if the stop lights go on and off normally when the brake pedal is operated and released.
NG Check and repair stop light circuit.
DI088-09

A11417
Battery FL
Main B
F6 F71 12
81
B Fusible
Link BlockEngine Room J/B
2G 2B E8B-RECM
BATT EFI No.1
II1 10
B-R DI-136
- DIAGNOSTICSENGINE
292 Author
: Date
:
2001 AVALON (RM808U)
DTC P1600 ECM BATT Malfunction
CIRCUIT DESCRIPTION
Battery positive voltage is supplied to terminal BATT of the ECM even when the ignition switch is OFF for
use by the DTC memory and air-fuel ratio adaptive control value memory, etc.
DTC No.DTC Detecting ConditionTrouble Area
P1600Open in back up power source circuit
Open in back up power source circuit

ECM
HINT:
If DTC P1600 appear, the ECM does not store another DTC.
WIRING DIAGRAM
INSPECTION PROCEDURE
HINT:
Read freeze frame data using TOYOTA hand-held tester or OBD II scan tool. Because freeze frame records
the engine conditions when the malfunction is detected. When troubleshooting, it is useful for determining
whether the vehicle was running or stopped, the engine was warmed up or not, the air-fuel ratio was lean
or rich, etc. at the time of the malfunction.
DI089-09

DI-138
- DIAGNOSTICSENGINE
294 Author
: Date
:
2001 AVALON (RM808U)
DTC P1656 OCV Circuit Malfunction (bank 1)
DTC P1663 OCV Circuit Malfunction (bank 2)
CIRCUIT DESCRIPTION
Refer to DTC P1349, P1354 on page DI-127.
DTC No.DTC Detecting ConditionTrouble Area
P1656
P1663Open or short in oil control valve circuit

Open or short in OCV circuit

OCV

ECM
WIRING DIAGRAM
Refer to DTC P1349, P1354 on page DI-127.
INSPECTION PROCEDURE
HINT:

If DTC P1656 dysplayed, check left bank OCV circuit.

If DTC P1663 dysplayed, check right bank OCV circuit.

Read freeze frame data using TOYOTA hand-held tester or OBD II scan tool. Because freeze frame
records the engine conditions when the malfunction is detected. When troubleshooting, it is useful for
determining whether the vehicle was running or stopped, the engine was warmed up or not, the air-fuel
ratio was lean or rich, etc. at the time of the malfunction.
TOYOTA hand-held tester:
1 Check OCV circuit.
PREPARATION:
(a) Start the engine and warmed it up.
(b) Connect the TOYOTA hand-held tester and select the VVT from the ACTIVE TEST menu.
CHECK:
Check the engine speed when operate the OCV by the TOYOTA hand-held tester.
OK:
VVT system is OFF (OCV is OFF): Normal engine speed
VVT system is ON (OCV is ON): Rough idle or engine stalled
OK Check for intermittent problems
(See page DI-3).
NG
DI6TC-01

- DIAGNOSTICSENGINE
DI-141
297 Author
: Date
:
2001 AVALON (RM808U)
DTC P1780 Park/Neutral Position Switch Malfunction
CIRCUIT DESCRIPTION
The park/neutral position switch go on when the shift lever is in the N or P shift position. When it goes on,
terminal NSW of the ECM is grounded to body ground via the starter relay, thus the terminal NSW voltage
becomes 0V. When the shift lever is in the D, 2, L or R position, the park/neutral position switch goes off,
so the voltage of ECM. Terminal NSW becomes battery voltage, the voltage of the ECM internal power
source. If the shift lever is moved from the N position to the D position, this signal is used for air-fuel ratio
correction and for idle speed control (estimated control), etc.
DTC No.DTC Detecting ConditionTrouble Area
P1780
When driving under conditions (a) and (b) for 30 sec. or more
the park/neutral position switch is ON (N position): (2 trip
dt ti l i)

Short in park/neutral position switch circuit
P k/ t l iti it hP1780detection logic)
(a) Vehicle speed: 40 km/h (25 mph) or more
(b) Engine speed: 1,500 - 4,000 rpm
Park/neutral position switch

ECM
HINT:
After confirming DTC P1780, use the TOYOTA hand-held tester to confirm the PNP switch signal from the
CURRENT DATA.
WIRING DIAGRAM
Refer to DTC P1780 on page DI-199.
INSPECTION PROCEDURE
Refer to DTC P1780 on page DI-199.
HINT:
Read freeze frame data using TOYOTA hand-held tester or OBD II scan tool. Because freeze frame records
the engine conditions when the malfunction is detected. When troubleshooting, it is useful for determining
whether the vehicle was running or stopped, the engine was warmed up or not, the air-fuel ratio was lean
or rich, etc. at the time of the malfunction.
DI08A-09

- 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

DI-54
- DIAGNOSTICSENGINE
210 Author
: Date
:
HINT:

When the DTC P0171 or P0174 is recorded, the actual air-fuel ratio is on the lean side. When DTC
P0172 or P0175 is recorded, the actual air-fuel ratio is on the rich side.

If the vehicle runs out of fuel, the air-fuel ratio is lean and DTC P0171 or P0174 is recorded. The MIL
then comes on.

If the total of the short-term fuel trim value and the long-term fuel trim value is within + 35 % (80°C
(176°F) or more), the system is functioning normally.

The A/F sensors (bank 1, 2 sensor 1) output voltage and the short-term fuel trim value can be read
using the OBD II scan tool or hand-held tester.

The ECM controls the voltage of AFR+, AFL+, AFR- and AFL- terminals of ECM to the fixed voltage.
Therefore, it is impossible to confirm the A/F sensor output voltage without OBD II scan tool or hand-
held tester.

OBD II scan tool (excluding hand-held tester) displays the one fifth of the A/F sensors (bank 1, 2 sen-
sor 1) output voltage which is displayed on the hand-held tester.
WIRING DIAGRAM
Refer to DTC P0125 on page DI-43.
INSPECTION PROCEDURE
HINT:
Read freeze frame data using TOYOTA hand-held tester or OBD II scan tool. Because freeze frame records
the engine conditions when the malfunction is detected. When troubleshooting, it is useful for determining
whether the vehicle was running or stopped, the engine was warmed up or not, the air-fuel ratio was lean
or rich, etc. at the time of the malfunction.
1 Check air induction system (See page SF-1).
NG Repair or replace.
OK
2 Check injector injection (See page SF-23).
NG Replace injector.
OK

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).

DI-8
- DIAGNOSTICSENGINE
164 Author
: Date
:
2001 AVALON (RM808U)
HINT:
Take care not to turn the ignition switch OFF. Turning the ignition
switch OFF switches the diagnosis system from the check
mode to the normal mode, so all DTC, etc. are erased.
(10) After checking the DTC, inspect the applicable cir-
cuit.
4. FAIL-SAFE CHART
If any of the following codes is recorded, the ECM enters fail-safe mode.
DTC No.Fail-Safe OperationFail-Safe Deactivation Conditions
P0100Ignition timing fixed at 10° BTDCReturned to normal condition
P0110Intake air temp. is fixed at 20°C (68°F)Returned to normal condition
P0115Engine coolant temp. is fixed at 80°C (176°F)Returned to normal condition
P0120VTA is fixed at 0°The following condition must be repeated at least 2 times con-
secutively 0.1 V
VTA
0.95 V, SPD = 0 km/h
P0135
P0141
P0155
P1135
P1155
The heater circuit in witch an abnormality is detected is
turned offIgnition switch OFF
P0325
P0330Max. timing retardationIgnition switch OFF
P1300Fuel cutReturned to normal condition
5. CHECK FOR INTERMITTENT PROBLEMS
TOYOTA hand-held tester only:
By putting the vehicle's ECM in the check mode, 1 trip detection logic is possible instead of 2 trip detection
logic and sensitivity to detect open circuits is increased. This makes it easier to detect intermittent problems.
(1) Clear the DTC (See step 2).
(2) Set the check mode (See step 3).
(3) Perform a simulation test (See page IN-20).
(4) Check the connector and terminal (See page IN-30).
(5) Handle the connector (See page IN-30).
6. BASIC INSPECTION
When the malfunction code is not confirmed in the DTC check, troubleshooting should be performed in order
for all possible circuits to be considered as the cause of the problems. In many cases, by carrying out the
basic engine check shown in the following flow chart, the location causing the problem can be found quickly
and efficiently. Therefore, use of this check is essential in engine troubleshooting.
1 Is battery positive voltage 11 V or more when engine is stopped?
NO Charge or replace battery.
YES
2 Is engine cranked?