2005 TOYOTA AVENSIS diagnostic

A73819A±A SectionAirSolid Electrolyte
(Zirconia Element)
Platinum
Electrode Heater
Exhaust Gas
Cover Element
A
A
ECM Monitored
A/F Sensor Voltage
Air±Fuel Ratio
± DIAGNOSTICSSFI SYSTEM (1AZ±FE)
05±249
AVENSIS REPAIR MANUAL (RM1018E)
DTC P2255/28 OXYGEN SENSOR REFERENCE GROUND
CIRCUIT LOW (FOR A/F SENSOR)(BANK 2
SENSOR 1)
DTC P2256/28 OXYGEN SENSOR REFERENCE GROUND
CIRCUIT HIGH (FOR A/F SENSOR)(BANK 2
SENSOR 1)
CIRCUIT DESCRIPTION
HINT:
This DTC is recorded when A/F sensor has a malfunction, although the caption is healed oxygen sensor.
The air±fuel ratio sensor are the lamination type. Compared to the conventional type, the sensor and heater
portions of the lamination type are narrower overall. Because the heat of the heater acts directly on the alumi-
na and zirconia (of the sensor portion) it accelerates the activation of the sensor.
To obtain a high purification rate of the CO, HC and NOx components of the exhaust gas, a three±way cata-
lytic converter is used. For the most efficient use of the three±way catalytic converter, the air±fuel ratio must
be precisely controlled so that it is always close to the stoichiometric air±fuel ratio.
The A/F sensor has the characteristic that it provides output voltage* being approximately proportional to
the existing air±fuel ratio. The A/F sensor output voltage* is used to provide feedback for the ECM to control
the air±fuel ratio.
By the A/F sensor output, the ECM can determine the deviation amount from the stoichiometric air±fuel ratio
and control the proper injection time immediately. If the A/F sensor is out of order, ECM is unable to perform
the accurate air±fuel ratio control.
The A/F sensor is equipped with a heater which heats the zirconia element. The heater is controlled by the
ECM. When the intake air volume is low (the temperature of the exhaust gas is low), the current flows to the
heater to heat the sensor for the accurate oxygen concentration detection.
*: The voltage value changes at the inside of the ECM only.

05±250
± DIAGNOSTICSSFI SYSTEM (1AZ±FE)
AVENSIS REPAIR MANUAL (RM1018E)DTC No.
DTC Detecting ConditionTrouble Area
A/F sensor circuit (bank 1 sensor 1)HINT : Main trouble area

Open or short in A/F sensor circuit
P2237/21
P2240/28
Conditions (a) and (b) continue for 5.0 sec. or more :
(a) AF+ less than 0.5 V
(b) AF+ greater than 4.5 V
Open or short in A/F sensor circuit

A/F sensor

A/F sensor heater
Conditions (a) and (b) continue for 5.0 sec. or more :
(a) (AF+) ± (AF±) less than 0.1 V
(b) (AF+) ± (AF±) greater than 0.8 V
A/F sensor heater

A/F sensor heater relay

A/F sensor heater and relay circuit

ECM
A/F sensor circuit low (bank 1 sensor 1)HINT : Main trouble area

Open in A/F sensor circuit
P2238/21
P2241/28Condition (a) continues for 5.0 sec. or more :
(a) AF+ less than 0.5 V
Open or short in A/F sensor circuit

A/F sensor

A/F sensor heater
Condition (a) continues for 5.0 sec. or more :
(a) (AF+) ± (AF±) less than 0.1 V
A/F sensor heater

A/F sensor heater relay

A/F sensor heater and relay circuit

ECM
A/F sensor circuit high (bank 1 sensor 1)HINT : Main trouble area

Short in A/F sensor circuit
P2239/21
P2242/28Condition (a) continue for 5.0 sec. or more :
(a) AF+ greater than 4.5 V
Open or short in A/F sensor circuit

A/F sensor

A/F sensor heater
Condition (a) continue for 5.0 sec. or more :
(a) (AF+) ± (AF±) greater than 0.8 V
A/F sensor heater

A/F sensor heater relay

A/F sensor heater and relay circuit

ECM
P2251/21
P2254/28Conditions (a) and (b) continue for 5.0 sec. or more :
(a) AF± less than 0.5 V
(b) AF± greater than 4.5 V
Open or short in A/F sensor circuit

A/F sensor

A/F sensor heaterP2252/21
P2255/28Condition (a) continue for 5.0 sec. or more :
(a) AF± less than 0.5 V
A/F sensor heater

A/F sensor heater relay


A/F sensor heater and relay circuitP2253/21
P2256/28Condition (a) continue for 5.0 sec. or more :
(b) AF± greater than 4.5 V
A/F sensor heater and relay circuit

ECM
HINT:

   
       means malfunction related
to bank 1 A/F sensor circuit.

         
means malfunction related
to bank 2 A/F sensor circuit.

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

Bank 2 refers to the bank that includes cylinder No. 2.

A76886
IE12
GRECM
MREL 8
E9
44
31
52A/F
Relay
Engine Room
R/B No.4 44
J12BR
D
J/C A/F 2
1
1A 11B±R
W±B Engine
Room
R/B No.1
Engine
Room
J/B No.1
EF ECBR J12 J/CJ13BR
D
EJ13
E B±G
Engine Room
J/B No.4 4A
4B 1 1
B±G
FL MAIN
BatteryW
W
GR
2EA11
EA1
W
W
2
4 A7
A/F Sensor
(Bank 1 Sensor 1)
1
36
E12 HA1A
23
E12 A1A+
31
E12A1A±
(*1)W
B L
A8
A/F Sensor
(Bank 2 Sensor 1)
5
E12 HA2A
22
E12 A2A+
30
E12A2A±
(*1) 2
41
3
L Y
G
*1: Shielded
± DIAGNOSTICSSFI SYSTEM (1AZ±FE)
05±251
AVENSIS REPAIR MANUAL (RM1018E)
WIRING DIAGRAM

05±252
± DIAGNOSTICSSFI SYSTEM (1AZ±FE)
AVENSIS REPAIR MANUAL (RM1018E)
INSPECTION PROCEDURE
HINT:
Hand±held tester only:
Narrowing down the trouble area is possible by performing ACTIVE TEST of the following ºA/F CONTROLº
(A/F sensor, heated oxygen sensor or other trouble areas can be distinguished).
(a) Perform ACTIVE TEST using the hand±held tester (A/F CONTROL).
HINT:
ºA/F CONTROLº is an ACTIVE TEST which changes the injection volume ±12.5 % or +25 %.
(1) Connect the hand±held tester to the DLC3 on the vehicle.
(2) Turn the ignition switch ON.
(3) Warm up the engine with the engine speed at 2,500 rpm for approximately 90 sec.
(4) Select the item ºDIAGNOSIS / OBD/MOBD / ACTIVE TEST / A/F CONTROLº.
(5) Perform ºA/F CONTROLº with the engine in an idle condition (press the right or left button).
Result:
A/F sensor reacts in accordance with increase and decrease of injection volume:
+25 %
rich output: Less than 3.0 V
±12.5 %
lean output: More than 3.35 V
Heated oxygen sensor reacts in accordance with increase and decrease of injection volume:
+25 %
rich output: More than 0.55 V
±12.5 %
lean output: Less than 0.4 V
NOTICE:
There is a few second delay in the A/F sensor output, and there is about 20 seconds delay in the
heated oxygen sensor output.

+25 %
±12.5 %
More than 3.35 V
Less than 3.0 V
Case 1
Case 2
Case 3
Case 4
Output voltage of A/F sensor
(sensor 1)
Injection volume
Output voltage
Output voltage of heated oxygen
sensor (sensor 2)Mainly suspect
trouble area
OK
+25 %
±12.5 %
More than 3.35 V
Less than 3.0V
Injection volume
Output voltage
+25 %
±12.5 %
More than 0.55 V
Less than 0.4V
Injection volume
Output voltage
A/F sensor
(A/F sensor, heater, A/F sen-
sor circuit)
+25 %
±12.5 %
More than 0.55 V
Less than 0.4V
Injection volume
Output voltage
+25 %
±12.5 %
Injection volume
Output voltage
NG
+25 %
±12.5 %
Injection volume
Output voltage
NG
+25 %
±12.5 %
Injection volume
Output voltage
NG
+25 %
±12.5 %
Injection volume
Output voltage
NGExtremely rich or lean actual
air±fuel ratio
(Injector, fuel pressure, gas
leakage in exhaust system,
etc.) OK
OK
OK
No reaction
No reaction
No reaction No reaction


Heated oxygen sensor
(heated oxygen sensor,
heater, heated oxygen sensor
circuit)
± DIAGNOSTICSSFI SYSTEM (1AZ±FE)
05±253
AVENSIS REPAIR MANUAL (RM1018E)
The following procedure of A/F CONTROL enables the technician to check and graph voltage output of both
the A/F sensor and heated oxygen sensor.
For displaying the graph indication, enter ºACTIVE TEST/ A/F CONTROL/USER DATAº, then select ºAFS
B1S1 and O2S B1S2º or ºAFS B2S1 and O2S B2S2º by pressing ºYESº button and push ºENTERº button
before pressing ºF4º button.
HINT:

If DTC   
        is displayed, check bank 1
sensor 1 circuit.

If DTC         
 is displayed, check bank 2
sensor 1 circuit.

Read freeze frame data using the hand±held tester. Freeze frame data records the engine conditions
when a 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.

A75325
HT
AF+ +B
AF±
Bank 1, Sensor 1 A7
A/F Sensor
A79112
Bank 2, Sensor 1 A8
A/F SensorHT
AF+ +B
AF±
B16200
05±254
± DIAGNOSTICSSFI SYSTEM (1AZ±FE)
AVENSIS REPAIR MANUAL (RM1018E)
1 INSPECT AIR FUEL RATIO SENSOR(RESISTANCE OF A/F SENSOR HEATER)
(a) Disconnect the A/F sensor connector.
(b) Measure resistance between terminals HT and +B of the
A/F sensor.
Resistance: 1.8 to 3.4
(20
C)
NG REPLACE AIR FUEL RATIO SENSOR
OK
2 INSPECT A/F RELAY
(a) Remove the A/F sensor heater relay from the engine
room R/B.
(b) Inspect the A/F senor heater relay.
Standard:
Terminal No.Specified condition
1 ± 2Continuity
No Continuity
3 ± 5Continuity
(Apply battery voltage Terminals 1 and 2)
NG REPLACE A/F RELAY
OK



A76787
Wire Harness Side
+B HT
A7Bank 1 Sensor 1
A/F Connector AF+
AF±
A79114
A8Bank 2 Sensor 1 Wire Harness Side
+B
HT
A/F Connector
AF+
AF±
A65745
E12
HA1AHA2AA1A±
A1A+
A2A±
A2A+
B62793
A/F Sensor A/F Relay
Heater
Sensor
A1A+ HA1A
Duty
Control ECM
From
Battery
A/F Fuse
A1A±
MREL Reference (Bank 1 Sensor 1 System Drawing)
± DIAGNOSTICSSFI SYSTEM (1AZ±FE)
05±255
AVENSIS REPAIR MANUAL (RM1018E)
3 CHECK HARNESS AND CONNECTOR(ECM ± A/F SENSOR)
(a) Disconnect the A7 or A8 A/F sensor connector.
(b) Disconnect the E12 ECM connector.
(c) Check for continuity between the wire harness side con-
nectors.
Standard (Check for open):
Symbols (Terminal No.)Specified condition
AF+ (A7±3) ± A1A+ (E12±23)
AF± (A7±4) ± A1A± (E12±31)
HT (A7±1) ± HA1A (E12±6)ContinuityAF+ (A8±3) ± A2A+ (E12±22)Continuity
AF± (A8±4) ± A2A± (E12±30)
HT (A8±1) ± HA2A (E12±5)
Standard (Check for short):
Symbols (Terminal No.)Specified condition
AF+ (A7±3) or A1A+ (E12±23) ± Body ground
AF± (A7±4) or A1A± (E12±31) ± Body ground
HT (A7±1) or HA1A (E12±6) ± Body groundNo continuityAF+ (A8±3) or A2A+ (E12±22) ± Body groundNo continuity
AF± (A8±4) or A2A± (E12±30) ± Body ground
HT (A8±1) or HA2A (E12±5) ± Body ground

05±256
±
DIAGNOSTICS SFI SYSTEM(1AZ±FE)
AVENSIS REPAIR MANUAL (RM1018E)
NGREPAIR OR REPLACE HARNESS OR CONNECTOR
OK
CHECK AND REPLACE ECM (See page 01±32)