Vacuum Sensor For Hydrocarbon ADSORBER Catalyst System: Prius

WARNING: This page does not describe the selected car, but rather 10 other vehicles, including the 2002 Toyota Tacoma, 2002 Toyota RAV4, 2002 Toyota Prius, 2002 Toyota MR2, and 2002 Toyota Highlander. However, it is still accessible from the selected car via links, so may be relevant.

NOTE: Hydrocarbon adsorber catalyst system may also be referred to as HCAC system.

WARNING: Read service precautions before proceeding with service procedure. See SERVICE PRECAUTIONS .

Ensure ignition is off. To test vacuum sensor supply voltage, disconnect electrical connector from vacuum sensor. Vacuum sensor is located at passenger's side front corner of engine and contains Black 3-pin electrical connector with Brown, Violet/White and Yellow/Red wires. See Fig 1.
Turn ignition on. Using voltmeter, check vacuum sensor supply voltage between terminals E2 and VC on wiring harness side of electrical connector for vacuum sensor. See Fig 2. E2 and VC terminals are the 2 outer terminals. DO NOT use center terminal.
Vacuum sensor supply voltage should be 4.5-5.5 volts. If vacuum sensor supply voltage is not within specification, check wiring circuit. See WIRING DIAGRAMS article. If vacuum sensor supply voltage is within specification, turn ignition off. Reinstall electrical connector on vacuum sensor.
To test vacuum sensor output voltage, disconnect vacuum hose from vacuum sensor. Remove glove box for access to Engine Control Module (ECM). For illustration of ECM location, see THEORY & OPERATION article.
Note ECM electrical connector terminals. See Figure. Connect voltmeter between terminals No. 14 (Violet/White wire) at ECM electrical connector E9 and No. 18 (Brown wire) at ECM electrical connector E8. See Figure. This is the HCLS and E1 terminals at ECM.

Turn ignition on. Measure and record vacuum sensor output voltage under ambient atmospheric pressure. Attach vacuum pump to bottom of vacuum sensor. Apply vacuum in specified increments and measure vacuum sensor output voltage drop at each increment. See VACUUM SENSOR OUTPUT VOLTAGE DROP SPECIFICATIONS table. Turn ignition off. Replace vacuum sensor if vacuum sensor output voltage drop is not within specification.

VACUUM SENSOR OUTPUT VOLTAGE DROP SPECIFICATIONS

Applied Vacuum - In. Hg	Voltage Drop
3.94	.3-.5
7.87	.7-.9
11.81	1.1-1.3
15.75	1.5-1.7
19.69	1.9-2.1

Fig 1: Locating Vacuum Sensor For Hydrocarbon Adsorber Catalyst System (Prius)

Fig 2: Checking Vacuum Sensor Supply Voltage (Prius)