Page 1977 of 2000

2AZ-FE ENGINE CONTROL SYSTEM – SFI SYSTEMES–89
ES
TYPICAL MALFUNCTION THRESHOLDS
P0037:
P0038:
P0141 (Heater performance monitor check):
COMPONENT OPERATING RANGE
WIRING DIAGRAM
Refer to DTC P0136 (see page ES-136).
CONFIRMATION DRIVING PATTERN
These DTCs are detected when the engine idles for 110 seconds or more.
INSPECTION PROCEDURE
HINT:
Sensor 2 refers to the sensor mounted behind the Three-Way Catalytic Converter (TWC) and located far
from the engine assembly.
Read freeze frame data using the intelligent tester. Freeze frame data records the engine condition when
malfunctions are detected. When troubleshooting, freeze frame data can help determine if the vehicle was
moving or stationary, 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) Disconnect the B19 Heated Oxygen (HO2) sensor
connector.
(b) Measure the resistance of the HO2 sensor connector.
Standard resistance
(c) Reconnect the HO2 sensor connector.
NG
OK
Accumulated heater ON time 100 seconds or more
Heater current Less than 0.3 A
Heater current More than 2 A
Accumulated heater resistance Varies with sensor element temperature (Example: More than 23
)
Heated Oxygen (HO2) sensor heater current0.4 to 1 A (when engine idles, HO2 sensor warmed up and battery
voltage 11 to 14 V)
1INSPECT HEATED OXYGEN SENSOR (HEATER RESISTANCE)
A115661E02
Tester Connections Specified Conditions
1 (HT1B) - 2 (+B) 11 to 16
at 20C (68F)
1 (HT1B) - 4 (E2) 10 k
or higher
REPLACE HEATED OXYGEN SENSOR
Page 1978 of 2000
ES–902AZ-FE ENGINE CONTROL SYSTEM – SFI SYSTEM
ES
(a) Disconnect the B19 HO2 sensor connector.
(b) Turn the ignition switch ON.
(c) Measure the voltage between the terminals of the B19
HO2 sensor connector and body ground.
Standard voltage
(d) Reconnect the HO2 sensor connector.
OK
NG
NG
OK
2CHECK TERMINAL VOLTAGE (+B OF HO2 SENSOR)
A072895E07
Tester Connections Specified Conditions
B19-2 (+B) - Body ground 9 to 14 V
Go to step 5
3INSPECT INTEGRATION RELAY (EFI MAIN RELAY) (See page ES-84)
REPLACE INTEGRATION RELAY
Page 1979 of 2000
2AZ-FE ENGINE CONTROL SYSTEM – SFI SYSTEMES–91
ES
(a) Check the EFI No. 1 fuse.
(b) Disconnect the B19 HO2 sensor connector.
(c) Remove the integration relay from the engine room No. 1
relay block.
(d) Check the resistance.
Standard resistance (Check for open)
Standard resistance (Check for short)
(e) Reconnect the HO2 sensor connector.
(f) Reinstall the integration relay.
NG
OK
4CHECK HARNESS AND CONNECTOR (HO2 SENSOR - EFI RELAY)
A127734E01
Tester Connections Specified Conditions
B19-2 (+B) - 1A-4 (Engine room No. 1
R/B)Below 1
Tester Connections Specified Conditions
B19-2 (+B) or 1A-4 (Engine room No.
1 R/B) - Body ground10 k
or higher
REPAIR OR REPLACE HARNESS OR
CONNECTOR
CHECK ECM POWER SOURCE CIRCUIT
Page 1980 of 2000

ES–922AZ-FE ENGINE CONTROL SYSTEM – SFI SYSTEM
ES
(a) Disconnect the B19 HO2 sensor connector.
(b) Disconnect the B30 ECM connector.
(c) Measure the resistance.
Standard resistance (Check for open)
Standard resistance (Check for short)
(d) Reconnect the HO2 sensor connector.
(e) Reconnect the ECM connector.
NG
OK
(a) Connect the intelligent tester to the DLC3.
(b) Turn the ignition switch ON.
(c) Turn the tester ON.
(d) Clear DTCs (see page ES-35).
(e) Start the engine.
(f) Allow the engine to idle for 2 minutes or more.
(g) Select the following menu items: DIAGNOSIS /
ENHANCED OBD II / DTC INFO / CURRENT CODES.
(h) Read DTCs.
Result
B
A
5CHECK HARNESS AND CONNECTOR (HO2 SENSOR - ECM)
A104950E05
Tester Connections Specified Conditions
B19-1 (HT1B) - B30-47 (HT1B) Below 1
Tester Connections Specified Conditions
B19-1 (HT1B) or B30-47 (HT1B) -
Body ground10 k
or higher
REPAIR OR REPLACE HARNESS OR
CONNECTOR
6CHECK WHETHER DTC OUTPUT RECURS
Display (DTC Output) Proceed To
No output A
P0037, P0038 and/or P0141 B
REPLACE ECM
CHECK FOR INTERMITTENT PROBLEMS
Page 1981 of 2000

2AZ-FE ENGINE CONTROL SYSTEM – SFI SYSTEMES–93
ES
DESCRIPTION
The Mass Air Flow (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 the 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 given temperature. The flow of
incoming air cools both the wire and an internal thermistor, affecting their resistance. To maintain a
constant current value, the ECM varies the voltage applied to these components in the MAF meter. The
voltage level is proportional to the airflow through the sensor, and the ECM uses it to calculate the intake
air volume.
The circuit is constructed so that the platinum hot wire and the temperature sensor create a bridge circuit,
and the power transistor is controlled so that the potentials of A and B remain equal to maintain the
predetermined temperature.
HINT:
When any of these DTCs are set, the ECM enters fail-safe mode. During fail-safe mode, the ignition
timing is calculated by the ECM, according to the engine RPM and throttle valve position. Fail-safe mode
continues until a pass condition is detected.
DTC P0100 Mass or Volume Air Flow Circuit
DTC P0102 Mass or Volume Air Flow Circuit Low Input
DTC P0103 Mass or Volume Air Flow Circuit High Input
DTC No. DTC Detection Conditions Trouble Areas
P0100MAF meter voltage less than 0.2 V, or more than 4.9 V for 3
seconds
(1 trip detection logic)• Open or short in MAF meter circuit
• MAF meter
•ECM
P0102MAF meter voltage less than 0.2 V for 3 seconds
(1 trip detection logic)• Open or short in MAF meter circuit
• MAF meter
•ECM
P0103MAF meter voltage more than 4.9 V for 3 seconds
(1 trip detection logic)• Open or short in MAF meter circuit
• MAF meter
•ECM
A140749E02
Page 1982 of 2000

ES–942AZ-FE ENGINE CONTROL SYSTEM – SFI SYSTEM
ES
HINT:
When any of these DTCs are set, check the air-flow rate by selecting the following menu items on the
intelligent tester: DIAGNOSIS / ENHANCED OBD II/ DATA LIST / PRIMARY / MAF.
MONITOR DESCRIPTION
If there is a defect in the MAF meter or an open or short circuit, the voltage level deviates from the normal
operating range. The ECM interprets this deviation as a malfunction in the MAF meter and sets a DTC.
Example:
When the sensor output voltage remains less than 0.2 V, or more than 4.9 V, for more than 3 seconds, the
ECM sets a DTC.
If the malfunction is not repaired successfully, a DTC is set 3 seconds after the engine is next started.
MONITOR STRATEGY
TYPICAL ENABLING CONDITIONS
TYPICAL MALFUNCTION THRESHOLDS
P0100:
P0102:
P0103:
COMPONENT OPERATING RANGE
Mass Air Flow Rate (g/sec.) Malfunctions
Approximately 0.0• Open in Mass Air Flow (MAF) meter power source circuit
• Open or short in VG circuit
271.0 or more • Open in E2G circuit
Related DTCsP0100: MAF meter range check (Fluctuating)
P0102: MAF meter range check (Low voltage)
P0103: MAF meter range check (High voltage)
Required Sensors/Components (Main) MAF meter
Required Sensors/Components (Related) Crankshaft position sensor
Frequency of Operation Continuous
Duration 3 seconds
MIL OperationImmediate: Engine RPM less than 4,000 rpm
2 driving cycles: Engine RPM 4,000 rpm or more
Sequence of Operation None
Monitor runs whenever following DTCs not present None
MAF meter voltage Less than 0.2 V, or more than 4.9 V
MAF meter voltage Less than 0.2 V
MAF meter voltage More than 4.9 V
MAF meter voltage Between 0.4 V and 2.2 V
Page 1983 of 2000

2AZ-FE ENGINE CONTROL SYSTEM – SFI SYSTEMES–95
ES
WIRING DIAGRAM
INSPECTION PROCEDURE
HINT:
Read freeze frame data using the intelligent tester. Freeze frame data records the engine condition when
malfunctions are detected. When troubleshooting, freeze frame data can help determine if the vehicle was
moving or stationary, 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) Connect the intelligent tester to the DLC3.
(b) Start the engine.
(c) Turn the tester ON.
(d) Select the following menu items: DIAGNOSIS /
ENHANCED OBD II / DATA LIST / PRIMARY / MAF.
(e) Read the values displayed on the tester.
Result
HINT:
*1: The value must change when the throttle valve is
open or closed with the engine running.
B
C
1READ VALUE USING INTELLIGENT TESTER (MASS AIR FLOW RATE)
A127248E02
Mass Air Flow Rate (g/sec.) Proceed To
0.0 A
271.0 or more B
Between 1.0 and 270.0 (*1) C
Go to step 6
CHECK FOR INTERMITTENT PROBLEMS
Page 1984 of 2000
ES–962AZ-FE ENGINE CONTROL SYSTEM – SFI SYSTEM
ES
A
(a) Disconnect the B1 Mass Air Flow (MAF) meter
connector.
(b) Turn the ignition switch ON.
(c) Measure the voltage between the terminal of the wire
harness side connector and body ground.
Standard voltage
(d) Reconnect the MAF meter connector.
NG
OK
(a) Output voltage inspection.
(1) Apply battery voltage across terminals +B and E2G.
(2) Connect the positive (+) tester probe to terminal VG,
and negative (-) tester probe to terminal E2G.
(3) Measure the voltage.
Standard voltage
NG
OK
2INSPECT MASS AIR FLOW METER (POWER SOURCE VOLTAGE)
A127724E01
Tester Connections Specified Conditions
B1-3 (+B) - Body ground 9 to 14 V
Go to step 5
3INSPECT MASS AIR FLOW METER (VG VOLTAGE)
A127786E02
Tester Connections Specified Conditions
5 (VG) - 4 (E2G) 0.2 to 4.9 V
REPLACE MASS AIR FLOW METER