TOYOTA PREVIA 91-97 REPAIR MANUAL

DRIVEABILITY AND EMISSIONS CONTROLS 4-25

Thermistor

Platinum Hot

Wire

Fig. 74 Cutaway view of the thermistor in the airflow meter

Between

terminals

THA - E2

THA - E2

THA - E2

THA - E2

THA - E2

THA - E2

Resistance

10 - 20 kO

4 - 7kQ

2 - 3kQ

0.9 - 1.3 kO

0.4 - 0.7 kO

0.2 - 0.4 kQ

Temperature

-20°C (~4°F)

0°C (32° F)

20° C (68° F)

40° C (104°F)

60°C (140°F)

80°C(176°F)

90914G58

Fig. 76 Mass Airflow Meter resistance values — 2TZ-FZE engine

hot wire and thermistor are located in the intake air bypass of the housing

detect any changes in the intake air temperature.

The hot wire is maintained at the set temperature controlling by the cur-

rent flow though the hot wire. This current flow is then measured as the

output voltage of the air flow meter.

TESTING

I See Figures 75, 76 and 77
Testing can be done without removing the MAP meter from the vehi-
cle.

1. If necessary, remove the MAP meter from the vehicle.


2. Disconnect the wiring from the airflow meter.


3. Using an ohmmeter, measure the resistance between each terminal
   (THA and E2) as shown in the charts.


4. If the resistance is not as specified, replace the air flow meter.


5. Inspect the meter operation. Connect the MAP meter wiring.


6. Connect a voltmeter to the positive (+) test probe to the VG and the
   negative (-) test probe to terminal E3.


7. Blow air into the meter and check that the voltage fluctuates.


8. If the operation is not as specified, replace the MAP meter.

Ohmmeter

nrn

o

o

o

E2X

Fig. 75 Mass air flow meter terminal identification—2TZ-FZE

engine

Voltmeter

E3-

Fig. 77 Attach the test probe terminals to the E3 (first pin) and

VG (fourth pin) from the left of the MAF meter—2TZ-FZE engine

REMOVAL & INSTALLATION

t See Figure 78

1. Disconnect the negative battery cable. Wait at least 90 seconds
   before proceeding on models with an airbag.

** CAUTION

Some models covered by this manual may be equipped with a

Supplemental Restraint System (SRS), which uses an air bag.

Whenever working near any of the SRS components, such as the

impact sensors, the air bag module, steering column and instru-

ment panel, disable the SRS, as described in Section 6.

2. Disconnect the air flow meter wiring harness from the unit.


3. Disconnect the A/C idle-up valve wiring.


4. Separate the A/C idle-up air hoses form the valve.


5. Loosen the air cleaner hose clamp.


6. Loosen the 4 clips, and remove the air cleaner cap with MAP meter
   as an assembly off the engine.


7. Remove the MAP meter retaining bolts.