2001 TOYOTA AVALON Service Repair Manual

- DIAGNOSTICSENGINE
DI-45
201 Author
: Date
:
2001 AVALON (RM808U)
1 Are there any other codes (besides DTC P0125) being output?
YES Go to relevant DTC chart (See page DI-14).
NO
2 Connect the OBD II scan tool or TOYOTA hand-held tester, and read value for
voltage output of A/F sensor (bank 1, 2 sensor 1).
PREPARATION:
(a) Connect the OBD II scan tool or TOYOTA hand-held tester to the DLC3.
(b) Warm up the A/F sensor with the engine speed at 2,500 rpm for approx. 90 sec.
CHECK:
Read the voltage value of the A/F sensor on the screen of OBDII scan tool or TOYOTA hand-held tester
when you perform all the following conditions.
HINT:
The voltage of the AFR+ or AFL+ terminal of the ECM is fixed at 3.3 V and the voltage of the AFR- or AFL-
terminal is fixed at 3.0 V. Therefore, it is impossible to check the A/F sensor output voltage at the terminals
(AFR+, AFL+/AFR-, AFL-) of the ECM.
OK:
ConditionA/F Sensor Voltage Value
Engine idling
Engine racing
Not remains at 3.30 V (0.660 V*)

Not remains at38V(076V*) or moreDriving at engine speed 1,500 rpm or more and vehicle
speed 40 km/h (25 mph) or more, and operate throttle valve
open and close
Not remains at 3.8 V (0.76 V*) or more

Not remains at 2.8 V (0.56 V*) or less
*: When you use OBD II scan tool (excluding TOYOTA hand-held tester)
HINT:

During fuel enrichment, there is a case that the output voltage of the A/F sensor is below 2.8 V (0.56
V*), it is normal.

During fuel cut, there is a case that the output voltage of the A/F sensor is above 3.8 V (0.76 V*), it
is normal.

If the output voltage of the A/F sensor remains at 3.30 V (0.660 V*) even after performing all the above
conditions, the A/F sensor circuit may be open.

If the output voltage of the A/F sensor remains at 3.8 V (0.76 V*) or more, or 2.8 V (0.56 V*) or less
even after performing all the above conditions, the A/F sensor circuit may be short.
*: When you use the OBD II scan tool (excluding TOYOTA hand-held tester).
OK Go to step 9.
NG

DI-46
- DIAGNOSTICSENGINE
202 Author
: Date
:
2001 AVALON (RM808U)
3 Check for open and short in harness and connector between ECM and A/F sen-
sor (bank 1, 2 sensor 1) (See page IN-30).
NG Repair or replace harness or connector.
OK
4 Check resistance of A/F sensor heater (bank 1, 2 sensor 1) (See page SF-79).
NG Replace A/F sensor.
OK
5 Check air induction system (See page SF-1).
NG Repair or replace.
OK
6 Check fuel pressure (See page SF-6).
NG Check and repair fuel pump, pressure regulator,
fuel pipe line and filter (See page SF-1).
OK
7 Check injector injection (See page SF-23).
NG Replace injector.
OK

- DIAGNOSTICSENGINE
DI-47
203 Author
: Date
:
2001 AVALON (RM808U)
8 Check gas leakage on exhaust system.
NG Repair or replace
OK
Replace A/F sensor (bank 1, 2 sensor 1).
9 Perform confirmation driving pattern (See page DI-106).
Go
10 Is there DTC P0125 being output again?
YES Check and replace ECM (See page IN-30).
NO
11 Did vehicle runs out of fuel in past?
NO Check for intermittent problems
(See page DI-3).
YES
DTC P0125 is caused by running out of fuel.

DI-48
- DIAGNOSTICSENGINE
204 Author
: Date
:
2001 AVALON (RM808U)
DTC P0128 Thermostat Malfunction
CIRCUIT DESCRIPTION
If the water temperature becomes 75°C (167°F) or more, it is abnormal.
If not due to the thermostat malfunction, it is abnormal.
DTC No.DTC Detecting ConditionTrouble Area
P0128
Condition (a), (b) or (c):
(a) After starting engine at 20°C (68°F)
(b) After engine is warmed up
(c) THW < 75°C (167°F)
Thermostat

Cooling system

Engine coolant temp. sensor

ECM
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 thermostat (See page CO-1 1).
NG Replace thermostat.
YES
2 Are there any other codes (besides DTC P0128) being output?
YES Go to relevant DTC chart (See page DI-14).
NG
Check and replace ECM (See page IN-30).
DI6T2-01

- DIAGNOSTICSENGINE
DI-49
205 Author
: Date
:
2001 AVALON (RM808U)
DTC P0136 Oxygen Sensor Circuit Malfunction (Bank 1
Sensor 2)
CIRCUIT DESCRIPTION
Refer to DTC P0125 on page DI-43.
DTC No.DTC Detecting ConditionTrouble Area
P0136
Voltage output of heated oxygen sensor remains at 0.4 V or
more or 0.55 V or less when vehicle is driven at 50 km/h (31
mph) or more after engine is warmed up (2 trip detection logic)
Open or short in heated oxygen sensor circuit

Heated oxygen sensor
HINT:

Bank 1 refers to the bank that includes cylinder No.1.

Sensor 2 refers to the sensor farther away from the engine body.
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 Are there any other codes (besides DTC P0136) being output?
YES Go to relevant DTC chart (See page DI-14).
NO
2 Check for open and short in harness and connector between ECM and heated
oxygen sensor (See page IN-30).
NG Repair or replace harness or connector.
OK
DI07Q-09

DI-50
- DIAGNOSTICSENGINE
206 Author
: Date
:
2001 AVALON (RM808U)
3 Check output voltage of heated oxygen sensor.
PREPARATION:
(a) Connect the OBD II scan tool or TOYOTA hand-held tester to the DLC3.
(b) Warm up the engine to normal operating temperature.
CHECK:
Read the voltage output of the heated oxygen sensor when the engine is suddenly raced.
HINT:
Perform quick racing to 4,000 rpm 3 min. using the accelerator pedal.
OK:
Heated oxygen sensor output voltage: Alternates from 0.4 V or less to 0.6 V or more.
OK Check that each connector is properly con-
nected.
NG
Replace heated oxygen sensor.

A06104
ON
HTS
(+)
(-)
- DIAGNOSTICSENGINE
DI-51
207 Author
: Date
:
2001 AVALON (RM808U)
DTC P0141 Oxygen Sensor Heater Circuit Malfunction
(Bank 1 Sensor 2)
CIRCUIT DESCRIPTION
Refer to DTC P0125 on page DI-43.
DTC No.DTC Detecting ConditionTrouble Area
P0141
When heater operates, heater current exceeds 2.35 A (2 trip
detection logic)
Open or short in heater circuit of heated oxygen sensor
Htd htP0141Heater current of 0.2 A or less when heater operates (2 trip
detection logic)
Heated oxygen sensor heater

ECM
HINT:

Bank 1 refers to the bank that includes cylinder No.1.

Sensor 2 refers to the sensor farther away from the engine body.
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 voltage between terminal HTS of ECM connector and body ground.
PREPARATION:
(a) Remove the glove compartment (See page SF-82).
(b) Turn the ignition switch ON.
CHECK:
Measure the voltage between terminal HTS of the ECM con-
nector and body ground.
OK:
Voltage: 9 - 14 V
OK Check and replace ECM (See page IN-30).
NG
2 Check resistance of heated oxygen sensor heater (See page SF-81).
NG Replace heated oxygen sensor.
DI6T3-01

DI-52
- DIAGNOSTICSENGINE
208 Author
: Date
:
2001 AVALON (RM808U)
OK
Check and repair harness or connector between EFI main relay (Marking: EFI) and heated oxygen
sensor, and heated oxygen sensor and ECM (See page IN-30).