Lexus SC300 / Lexus SC400. Service manual — part 339

INSPECTION OF EGR VALVE

1.

REMOVE EGR VALVE
(a) Disconnect the following hoses:

(1) Vacuum hose from EGR vacuum modulator
(2) Pressure hose from EGR vacuum modulator

(USA Spec.)

(b) Disconnect the EGR Gas Temp. Sensor connector

(c) Loosen the nut for EGR pipe.
(d) Remove the two nuts, EGR valve and gasket.

2.

INSPECT EGR VALVE
Check for sticking and heavy carbon deposits.
If a problem is found, replace the EGR valve assembly.

3.

REINSTALL EGR VALVE
(a) Place a new gasket on the intake manifold.

(b) Install the EGR valve with the two nuts.

Torque: 18 N

⋅

m (185 kgf

⋅

cm, 13 ft

⋅

lbf)

(c) Torque the nut for EGR pipe.

Torque: 64 N

⋅

m (650 kgf

⋅

cm, 47 ft

⋅

lbf)

–

EMISSION CONTROL SYSTEMS

Exhaust Gas Recirculation (EGR) System

EC–15

(d) Connect the following hoses:

(1) Vacuum hose from EGR vacuum modulator
(2) Pressure hose from EGR vacuum modulator

(USA Spec.)

(e) Connect the EGR Gas Temp. Sensor connector.

EC–16

–

EMISSION CONTROL SYSTEMS

Exhaust Gas Recirculation (EGR) System

EXHAUST GAS RECIRCULATION (EGR) SYSTEM

DESCRIPTION

To reduce NOx emission, part of the exhaust gases are recirculated through the EGR valve to the intake

manifold to lower the maximum combustion temperature.

OPERATION

Coolant Temp.

Condition

EGR Valve

Exhaust Gas

Below 53

°

C (127

°

F)

–

CLOSED

Not recirculated

Above 55

°

C (131

°

F)

(a)

Idling, Deceleration, Neutral,
Low air volume, High Engine speed

CLOSED

Not recirculated

Above 55 C (131 F)

Except (a)

OPEN

*Recirculated

* The ECU calculates the appropriate number of steps according to the intake air volume and the engine speed, then
drives the stepping motor to maintain the EGR volume at a level appropriate to the driving conditions.

–

EMISSION CONTROL SYSTEMS

Exhaust Gas Recirculation (EGR) System

EC–15

OPERATION (Cont’d)

EC–16

–

EMISSION CONTROL SYSTEMS

Exhaust Gas Recirculation (EGR) System