2001 TOYOTA HIGHLANDER Service Repair Manual

driver seat adjustment turn signal mileage rims automatic transmission transmission oil

Page 1705 of 2572

TOYOTA HIGHLANDER 2001 Service Repair Manual A87979
+12.5 %
Normal Malfunction-12.5 %
0 3.3 V
1 VA/F Sensor Output
Heated Oxygen Sensor OutputInjection Volume
Malfunction
- DIAGNOSTICSSFI SYSTEM (2AZ-FE)
05-131
321 Author: Date:
2005 HIGHLANDE

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TOYOTA HIGHLANDER 2001 Service Repair Manual 05-132
- DIAGNOSTICSSFI SYSTEM (2AZ-FE)
322 Author: Date:
2005 HIGHLANDER REPAIR MANUAL (RM1144U)
DTC P0171 SYSTEM TOO LEAN (BANK 1)
DTC P0172 SYSTEM TOO RICH (BANK 1)
CIRCUIT DESCRIPTION
The fue

05-132
- DIAGNOSTICSSFI SYSTEM (2AZ-FE)
322 Author: Date:
2005 HIGHLANDER REPAIR MANUAL (RM1144U)
DTC P0171 SYSTEM TOO LEAN (BANK 1)
DTC P0172 SYSTEM TOO RICH (BANK 1)
CIRCUIT DESCRIPTION
The fuel trim is related to the feedback compensation value, not to the basic injection time. The fuel trim in-
cludes the short-term fuel trim and the long-term fuel trim.
The short-term fuel trim is the short-term fuel compensation used to maintain the ideal stoichiometric air-
fuel ratio. The signal from the A/F sensor indicates whether the air-fuel ratio is RICH or LEAN compared
to the stoichiometric air-fuel ratio. This variance triggers a reduction in the fuel volume if the air-fuel ratio
is RICH, and an increase in the fuel volume if it is LEAN.
The short-term fuel trim varies from the central value due to individual engine differences, wear over time
and changes in the operating environment. The long-term fuel trim, which controls overall fuel compensa-
tion, steadies long-term deviations of the short-term fuel trim from the central value.
If both the short-term fuel trim and the long-term fuel trim are LEAN or RICH beyond a certain value, it is
detected as a malfunction, the MIL is illuminated and a DTC is set.
DTC No.DTC Detection ConditionTrouble Area
P0171
When air-fuel ratio feedback is stable after warming up engine,
fuel trim is considerably in error on LEAN side
(2 trip detection logic)
Air induction system
Injector blockage
MAF meter
ECT sensor
Fuel pressure
Gas leakage in exhaust system
Open or short in A/F sensor (bank 1 sensor 1) circuit
A/F sensor (bank 1 sensor 1)
A/F sensor heater (bank 1 sensor 1)
EFI relay
Open or short in A/F sensor heater and EFI relay circuits
PCV hose connection
PCV hose
P0172
When air-fuel ratio feedback is stable after warming up engine,
fuel trim is considerably in error on RICH side
(2 trip detection logic)
Injector leak, blockage
MAF meter
ECT sensor
Ignition system
Fuel pressure
Gas leakage in exhaust system
Open or short in A/F sensor (bank 1 sensor 1) circuit
A/F sensor (bank 1 sensor 1)
A/F sensor heater
Open or short in A/F sensor heater and EFI relay circuits
EFI relay
HINT:
When DTC P0171 is recorded, the actual air-fuel ratio is on the LEAN side. When DTC P0172 is re-
corded, 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 is recorded. The MIL then illumi-
nates.
05ETQ-06

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TOYOTA HIGHLANDER 2001 Service Repair Manual A82386
Fuel Compensation
Amount1.35
1.0
0.65+34 (%): Threshold at LEAN
-34 (%): Threshold at RICH
- DIAGNOSTICSSFI SYSTEM (2AZ-FE)
05-133
323 Author: Date:
2005 HIGHLANDER REPAIR MANUAL (RM1144U)

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TOYOTA HIGHLANDER 2001 Service Repair Manual 05-134
- DIAGNOSTICSSFI SYSTEM (2AZ-FE)
324 Author: Date:
2005 HIGHLANDER REPAIR MANUAL (RM1144U)
TYPICAL ENABLING CONDITIONS
The monitor will run whenever these DTCs are not presentSee page 05-16

Page 1709 of 2572

TOYOTA HIGHLANDER 2001 Service Repair Manual +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)Ma

+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)Main 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
Almost
No reaction
Almost
No reaction
Almost
No reaction Almost
No reaction
'
Heated oxygen sensor
(heated oxygen sensor,
heater, heated oxygen sensor
circuit)
- DIAGNOSTICSSFI SYSTEM (2AZ-FE)
05-135
325 Author: Date:
2005 HIGHLANDER REPAIR MANUAL (RM1144U)
NOTICE:
The A/F sensor output has a few seconds of delay and the heated oxygen sensor output has about
20 seconds of delay at maximum.
The following A/F CONTROL procedure enables a technician to check and graph the voltage outputs of both
the A/F sensor and the heated oxygen sensor.
For displaying the graph, enter ºACTIVE TEST / A/F CONTROL / USER DATAº, select ºAFS B1S1 and O2S
B1S2º by pressing ºYESº and push ºENTERº. Then press ºF4º.
HINT:
Read freeze frame data using the hand-held tester or the OBD II scan tool. Freeze frame data records
the engine conditions when a malfunction is detected. When troubleshooting, freeze frame data can
help determine if the vehicle was running or stopped, if the engine was warmed up or not, if the air-fuel
ratio was lean or rich, and other data from the time the malfunction occurred.
A high A/F sensor voltage could be caused by a RICH air fuel mixture. Check the conditions that might
cause the engine to run with a RICH air fuel mixture.
A low A/F sensor voltage could be caused by a LEAN air fuel mixture. Check the conditions that might
cause the engine to run with a LEAN air fuel mixture.

Page 1710 of 2572

TOYOTA HIGHLANDER 2001 Service Repair Manual 05-136
- DIAGNOSTICSSFI SYSTEM (2AZ-FE)
326 Author: Date:
2005 HIGHLANDER REPAIR MANUAL (RM1144U)
1 CHECK AIR INDUCTION SYSTEM
(a) Check for vacuum leaks in air induction system.
OK: No vacuum lea

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TOYOTA HIGHLANDER 2001 Service Repair Manual A60548
32 1 4 5
-20 0 20 40 60 80 100 0.1 0.2 0.3 0.51 2 3 5 10 20 30
TemperatureC(F)
Resistance kW
(-4) (32) (80) (140)(104) (212)(176)
Air
VG
EVG+B
THA E2
Acceptable
- DIAGNOSTICSSFI SYSTEM (2AZ-F

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TOYOTA HIGHLANDER 2001 Service Repair Manual S01196S01699
30
20
10
5
3
02040 0.11
0.3
0.2 0.52
60 80 100 -20
(-4) (104) (140) (176)(32) (68) (212)
A81700
Ohmmeter
Acceptable
Temperature C (F)
Resistance kW
05-138
- DIAGNOSTICSSFI SYSTEM (2AZ-F

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