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Toyota Lexus LS400 sedan 1UZ-FE engine uses a Karman scroll airflow sensor, and its maintenance is mainly to measure the resistance and voltage value of each terminal.
Unplug the airflow sensor harness connector, use a multimeter to measure the resistance between terminals THA and E2 on the airflow sensor connector socket, as shown in Figure 1, the measurement result should meet the value specified in Figure 2, if not, replace the Airflow Sensors.
Insert the wiring harness connector of the sensor, use a multimeter to measure the voltage between the THA and E2, Vc and E1, and KS and E1 terminals of the connector, and they should meet the values specified in Figure 2.
If the measurement result does not match the standard value, check the line connection between the sensor and the ECU.
If the wiring harness is well connected, unplug the sensor connector and turn on the ignition switch.
Check the voltage between the power terminals Vc and E1 and the signal input terminals KS and E1.
If the voltages are both 4.5~5.5V, the ECU is working normally.
The airflow sensor should be replaced; if the voltage is not within the specified range, it indicates that the ECU is faulty, and the ECU should be replaced.
Check the voltage between the power terminals Vc and E1 and the signal input terminals KS and E1, as shown in Figure 3 and Figure 4.
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