2001 TOYOTA HIGHLANDER mass air flow

A76903
VG (+) EVG (-)
E7
ECM
Y
A54396
A81699
A85482
Wire Harness Side
M1
MAF Meter
EVG VG
E7
ECM
EVG
VG
- DIAGNOSTICSSFI SYSTEM (2AZ-FE)
05-85
275 Author
: Date
:
2005 HIGHLANDER REPAIR MANUAL (RM1144U)
3 INSPECT ECM (VG VOLTAGE)
(a) Start the engine.
(b) Measure the voltage of the ECM connector.
Standard:
Tester ConnectionConditionSpecified Condition
E7-30 (VG) - E7-29 (EVG)Engine is idling0.5 to 3.0 V
HINT:
The shift position should be P or N and the A/C switch should
be turned OFF.
OK REPLACE ECM (See page 10-9)
NG
4 CHECK WIRE HARNESS (MAF METER - ECM)
(a) Disconnect the M1 MAF meter connector.
(b) Disconnect the E7 ECM connector.
(c) Measure the resistance of the wire harness side connec-
tors.
Standard:
Tester ConnectionSpecified Condition
M1-3 (VG) - E7-30 (VG)
M1-2 (EVG) - E7-29 (EVG)Below 1 W
M1-3 (VG) or E7-30 (VG) - Body ground10 kW or higher
NG REPAIR OR REPLACE HARNESS AND
CONNECTOR
OK
REPLACE MASS AIR FLOW METER

Y
A54396
A81699
A85482
Wire Harness Side
M1
MAF Meter
EVG VG
E7
ECM
EVG
VG
- DIAGNOSTICSSFI SYSTEM (2AZ-FE)
05-87
277 Author
: Date
:
2005 HIGHLANDER REPAIR MANUAL (RM1144U)
7 CHECK WIRE HARNESS (MAF METER - ECM)
(a) Disconnect the M1 MAF meter connector.
(b) Disconnect the E7 ECM connector.
(c) Measure the resistance of the wire harness side connec-
tors.
Standard:
Tester ConnectionSpecified Condition
M1-3 (VG) - E7-30 (VG)
M1-2 (EVG) - E7-29 (EVG)Below 1 W
M1-3 (VG) or E7-30 (VG) - Body ground10 kW or higher
NG REPAIR OR REPLACE HARNESS AND
CONNECTOR
OK
REPLACE MASS AIR FLOW METER

05-88
- DIAGNOSTICSSFI SYSTEM (2AZ-FE)
278 Author
: Date
:
2005 HIGHLANDER REPAIR MANUAL (RM1144U)
DTC P0101 MASS OR VOLUME AIR FLOW CIRCUIT
RANGE/PERFORMANCE PROBLEM
CIRCUIT DESCRIPTION
Refer to DTC P0100 on page 05-81.
DTC No.DTC Detection ConditionTrouble Area
P0101

High voltage:
Conditions (a), (b) and (c) continue for more than 10 seconds
(2 trip detection logic):
(a) Engine speed less than 2,000 rpm
(b) Engine coolant temperature 70C (158F) or higher
(c) Voltage output of Mass Air Flow (MAF) meter more than 2.2
V (varies with Throttle Position [TP] sensor voltage)

Low voltage:
Conditions (a) and (b) continue for more than 10 seconds
(2 trip detection logic):
(a) Engine speed more than 300 rpm
(b) Voltage output of MAF meter less than 0.65 V
(varies with TP sensor voltage)

MAF meter
MONITOR DESCRIPTION
The MAF meter is a sensor that measures the amount of air flowing through the throttle valve. The ECM uses
this information to determine the fuel injection time and to provide an appropriate air-fuel ratio.
Inside the MAF meter, there is a heated platinum wire which is exposed to the flow of intake air. By applying
a specific electrical current to the wire, the ECM heats it to a specific temperature. The flow of incoming air
cools both the wire and an internal thermistor, changing their resistance. To maintain a constant current val-
ue, the ECM varies the voltage applied to these components of the MAF meter. The voltage level is propor-
tional to the air flow through the sensor, and the ECM uses it to calculate the intake air volume.
If there is a defect in the sensor, or an open or short in the circuit, the voltage level deviates from the normal
operating range. The ECM interprets this deviation as a malfunction in the MAF meter and sets the DTC.
Example:
If the voltage is more than 2.2 V, or less than 0.65 V while idling, the ECM determines that there is a malfunc-
tion in the MAF meter and sets the DTC.
MONITOR STRATEGY
Related DTCsP0101: MAF Meter Rationality (Low voltage)
P0101: MAF Meter Rationality (High voltage)
Required sensors/ components (Main)MAF meter
Required sensors/ components (Related)Crankshaft position sensor, ECT sensor, Throttle position sensor
Frequency of operationContinuous
Duration10 seconds
MIL operation2 driving cycles
Sequence of operationNone
051ZM-14

- DIAGNOSTICSSFI SYSTEM (2AZ-FE)
05-89
279 Author
: Date
:
2005 HIGHLANDER REPAIR MANUAL (RM1144U)
TYPICAL ENABLING CONDITIONS
All:
The monitor will run whenever this DTC is not presentSee page 05-16
MAF Meter Rationality (High Voltage):
Engine RPMLess than 2,000 rpm
ECT70°C (158°F) or more
MAF meter voltage4.9 V or less
MAF Meter Rationality (Low Voltage):
Engine RPMMore than 300 rpm
MAF meter voltage0.2 V or more
Fuel cutOFF
TYPICAL MALFUNCTION THRESHOLDS
MAF Meter Rationality (High Voltage):
MAF meter voltageMore than 2.2 V (varies with throttle position sensor voltage)
MAF Meter Rationality (Low Voltage):
MAF meter voltageLess than 0.65 V (varies with throttle position sensor voltage)
WIRING DIAGRAM
Refer to DTC P0100 on page 05-81.
INSPECTION PROCEDURE
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 deter-
mine 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.
1 CHECK OTHER DTC OUTPUT (IN ADDITION TO DTC P0101)
(a) Read the DTC using the hand-held tester or the OBD II scan tool.
Result:
Display (DTC Output)Proceed to
P0101 and other DTCs are outputA
Only P0101 is outputB
HINT:
If any other codes besides P0101 are output, perform the troubleshooting for those codes first.
B REPLACE MASS AIR FLOW METER
A
GO TO RELEVANT DTC CHART (See page 05-48)

- 20 0 20 40 60 80 100
(- 4) 32 68 104 140 176 212 30
20
10
5
3
2
1
0.5
0.3
0.2
0.1
A67628
Acceptable Fig. 1
Resistance kW
Temperature C (F)
05-90
- DIAGNOSTICSSFI SYSTEM (2AZ-FE)
280 Author
: Date
:
2005 HIGHLANDER REPAIR MANUAL (RM1144U)
DTC P0110 INTAKE AIR TEMPERATURE CIRCUIT
DTC P0112 INTAKE AIR TEMPERATURE CIRCUIT LOW
INPUT
DTC P0113 INTAKE AIR TEMPERATURE CIRCUIT HIGH
INPUT
CIRCUIT DESCRIPTION
The Intake Air Temperature (IAT) sensor, mounted on the Mass
Air Flow (MAF) meter, monitors the intake air temperature. The
IAT sensor has a thermistor that varies its resistance depending
on the temperature of the intake air. When the air temperature
is low, the resistance in the thermistor increases. When the tem-
perature is high, the resistance drops. The variations in resis-
tance are reflected as changes in voltage applied to the ECM
terminal (see Fig. 1).
The IAT sensor is connected to the ECM (see below). The 5 V
power source voltage in the ECM is applied to the IAT sensor
from terminal THA via resistor R.
That is, the resistor R and the IAT sensor are connected in se-
ries. When the resistance value of the IAT sensor changes in
accordance with changes in the IAT, the voltage at terminal THA
also changes. Based on this signal, the ECM increases the fuel
injection volume to improve the driveability during cold engine
operation.
DTC No.Proceed toDTC Detection ConditionTrouble Area
P0110Step 1
Open or short in IAT (Intake
air temperature) sensor cir-
cuit for 0.5 seconds
(1 trip detection logic)
Open or short in IAT sensor circuit

IAT sensor (built-in MAF meter)

ECM
P0112Step 4
Short in IAT sensor circuit for
0.5 seconds
(1 trip detection logic)

Same as DTC No. P0110
P0113Step 2
Open in IAT sensor circuit for
0.5 seconds
(1 trip detection logic)

Same as DTC No. P0110
HINT:
After confirming DTC P0110, P0112 or P0113, use the hand-held tester or the OBD II scan tool to confirm
the IAT from the ALL menu (to reach the ALL menu: DIAGNOSIS / ENHANCED OBD II / DATA LIST / ALL).
Temp. DisplayedMalfunction
-40°C (-40°F)Open circuit
140°C (284°F) or moreShort circuit
0596B-07

Y
A75743
A76903
A85506
M1
MAF MeterECM
THA
E2
Wire Harness Side
M1
MAF Meter
E2THA
Y
A75742
A76903A85507
M1
MAF MeterECM
THA
E2
E7
ECM THA
E2
- DIAGNOSTICSSFI SYSTEM (2AZ-FE)
05-93
283 Author
: Date
:
2005 HIGHLANDER REPAIR MANUAL (RM1144U)
2 READ VALUE OF HAND-HELD TESTER OR OBD II SCAN TOOL (CHECK FOR
OPEN IN HARNESS)
(a) Disconnect the M1 MAF meter connector.
(b) Connect terminals THA and E2 of the M1 MAF meter wire
harness side connector.
(c) Turn the ignition switch ON.
(d) On the hand-held tester or the OBD II scan tool, enter the
following menus: DIAGNOSIS / ENHANCED OBD II /
DATA LIST / ALL / INTAKE AIR. Read the values.
OK:
Temperature value: 1405C (2845F) or more
OK REPLACE MASS AIR FLOW METER (IAT SEN-
SOR)
NG
3 READ VALUE OF HAND-HELD TESTER OR OBD II SCAN TOOL (CHECK FOR
OPEN IN ECM)
(a) Disconnect the M1 MAF meter connector.
(b) Connect terminals THA and E2 of the E7 ECM connector.
HINT:
Before checking, do a visual and contact pressure check for the
ECM connector.
(c) Turn the ignition switch ON.
(d) On the hand-held tester or the OBD II scan tool, enter the
following menus: DIAGNOSIS / ENHANCED OBD II /
DATA LIST / ALL / INTAKE AIR. Read the values.
OK:
Temperature value: 1405C (2845F) or more
OK REPAIR OR REPLACE HARNESS OR
CONNECTOR
NG

A75766
ECM M1
MAF Meter
THA
E2
Y
A75744
A81699A85508
M1
MAF MeterECM
THA
E2
E7
ECM
05-94
- DIAGNOSTICSSFI SYSTEM (2AZ-FE)
284 Author
: Date
:
2005 HIGHLANDER REPAIR MANUAL (RM1144U)
CONFIRM GOOD CONNECTION AT ECM. IF OK, REPLACE ECM (See page 10-9)
4 READ VALUE OF HAND-HELD TESTER OR OBD II SCAN TOOL (CHECK FOR
SHORT IN HARNESS)
(a) Disconnect the M1 MAF meter connector.
(b) Turn the ignition switch ON.
(c) On the hand-held tester or the OBD II scan tool, enter the
following menus: DIAGNOSIS / ENHANCED OBD II /
DATA LIST / ALL / INTAKE AIR. Read the values.
OK:
Temperature value: -405C (-405F)
OK REPLACE MASS AIR FLOW METER
NG
5 READ VALUE OF HAND-HELD TESTER OR OBD II SCAN TOOL (CHECK FOR
SHORT IN ECM)
(a) Disconnect the E7 ECM connector.
(b) Turn the ignition switch ON.
(c) On the hand-held tester or the OBD II scan tool, enter the
following menus: DIAGNOSIS / ENHANCED OBD II /
DATA LIST / ALL / INTAKE AIR. Read the values.
OK:
Temperature value: -405C (-405F)
OK REPAIR OR REPLACE HARNESS OR
CONNECTOR
NG
REPLACE ECM (See page 10-9)

- DIAGNOSTICSSFI SYSTEM (2AZ-FE)
05-1 19
309 Author
: Date
:
2005 HIGHLANDER REPAIR MANUAL (RM1144U)DTC No.
DTC Detection ConditionTrouble Area

Following condition (a) (b) or (c) is met:
(a) During driving with engine warmed up, heated oxygen sen-
sor output does not change for 8 minutes
(b) Heated oxygen sensor output is very low most of time for

Open or short in heated oxygen sensor (bank 1 sensor 2)
ii
P0136
(b) Heated oxygen sensor out ut is very low most of time for
220 seconds
(c) The rear heated oxygen sensor voltage does not drop to
below 0.2 V immediately when vehicle decelerates and fuel
cut is operatingcircuit

Heated oxygen sensor (bank 1 sensor 2)

Heated oxygen sensor heater (bank 1 sensor 2)

A/F sensor


A/F sensor heatercut is o erating

Both (a) and (b) continue for more than 30 seconds:
(a) Estimated rear oxygen sensor temperature is less than
800C
(b) Rear oxygen sensor impedance is less than 5W
A/F sensor heater

EFI relay
P0137
Both (a) and (b) continue for more than 240 seconds:
(a) Estimated rear oxygen sensor temperature is more than
450C
(b) Rear oxygen sensor impedance is more than 15kW
Open or short in heated oxygen sensor (bank 1 sensor 2)
circuit (sensor to ECM)

Open or short in heated oxygen sensor (bank 1 sensor 2)
internal
P0138Rear oxygen sensor output voltage is over 1.2 V for more than
30 seconds
Short in heated oxygen sensor (bank 1 sensor 2) circuit

Short in heated oxygen sensor (bank 1 sensor 2) circuit

ECM internal circuit malfunction
MONITOR DESCRIPTION
The ECM monitors the rear heated oxygen sensor (HO2S) in the following 4 items:
1. The HO2S voltage changes between Rich (more than 0.45 V) and Lean (less than 0.45 V) while the vehicle
is running (repeating acceleration and deceleration) for 8 minutes. If not, the ECM interprets this as a mal-
function, illuminates the MIL, and then sets a DTC.
2. The HO2S voltage does not remain at less than 0.05 V for a long time while the vehicle is running (60 %
of the time in the 220 second-monitor, the sensor output is less than 0.05 V). If it does, the ECM interprets
this as a malfunction, illuminates the MIL, and then sets a DTC.
3. The sensor's voltage drops to below 0.2 V (extremely Lean status) immediately when the vehicle deceler-
ates and the fuel cut is working for 7 seconds. If not, the ECM interprets this to mean the sensor's response
feature has deteriorated, illuminates the MIL, and then sets a DTC.
4. The rear oxygen sensor impedance is 5 W or less, 15 kW or more, or output voltage is 1.2 V or more (normal
voltage: 0 to 1.0 V). If so, the ECM will determine that the rear oxygen sensor or a related circuit has an open
or short circuit, illuminates the MIL and sets a DTC.
Impedance is detected by the IC inside the ECM.
MONITOR STRATEGY
Related DTCs
P0136: Heated oxygen sensor output voltage (Output voltage)
P0136: Heated oxygen sensor impedance (Low impedance)
P0137: Heated oxygen sensor impedance (High impedance)
P0138: Heated oxygen sensor output voltage (High voltage)
P0138: Heated oxygen sensor output voltage (During fuel-cut)
Required Sensors/Components (Main)Heated oxygen sensor
Required Sensors/Components (Related)Crankshaft position sensor, engine coolant temperature sensor, mass air flow me-
ter and throttle position sensor
Frequency of OperationOnce per driving cycle: Active air-fuel ratio control detection
Continuous: Others
DurationWithin 480 seconds
MIL Operation
2 driving cycles: P0136 (Rear HO2S output voltage - case 1)
P0136 (Rear HO2S output voltage - case 2)
P0138 (Rear HO2S voltage during fuel-cut)
Immediate: Others
Sequence of OperationNone