Possible causes
– Faulty Exhaust Gas Temperature Sensor
– Exhaust Gas Temperature Sensor harness is open or shorted
– Exhaust Gas Temperature Sensor circuit poor electrical connection
– Hydro-Carbon Absorber and Catalyst (HCAC) valve stuck or actuator problem
– Exhaust Gas Temperature Sensor harness is open or shorted
– Exhaust Gas Temperature Sensor circuit poor electrical connection
– Hydro-Carbon Absorber and Catalyst (HCAC) valve stuck or actuator problem
Symptoms
– Engine Light ON (or Service Engine Soon Warning Light)
P1084 LEXUS Description
HCAC (Hydro-Carbon Absorber and Catalyst System) fault detected