DTC 0306

SYSTEM DESCRIPTION
The EGRC-BPT valve monitors exhaust pressure to activate the diaphragm, controlling throttle body vacuum applied to the EGR valve. In other words, recirculated exhaust gas is controlled in response to positioning of the EGR valve or to engine operation.






ON BOARD DIAGNOSIS LOGIC
If too much EGR flow exists due to an EGRC-BPT valve malfunction, oft idle engine roughness will increase. If the roughness is excessive, then the vacuum to the EGR valve is interrupted through the EGRC-solenoid valve. If the engine roughness is reduced at that time, the EGRC-BPT valve malfunction is indicated.


DIAGNOSTIC TROUBLE CODE CONFIRMATION PROCEDURE

CAUTION: Always drive vehicle at a sate speed.

NOTE: If "DIAGNOSTIC TROUBLE CODE CONFIRMATION PROCEDURE" has been previously conducted, always turn ignition switch "OFF" and wait at least 5 seconds before conducting the next test.

TESTING CONDITION:
Always perform the test at a temperature of -10°C (14°F) or higher.


OVERALL FUNCTION CHECK

WARNING: Be careful not to burn yourself, as the engine may be hot. Use this procedure to check the overall function of the EGRC-BPT valve. During the check, a 1st trip DTC might not be confirmed.









(1) Disconnect the rubber hose to the collector from the EGRC solenoid valve at the collector.
(2) Disconnect the rubber hose to the EGRC-solenoid valve from the EGRC-BPT valve at the vacuum gallery B (EGRC-solenoid valve side).
(3) Connect between the collector and the vacuum gallery B (EGRC-solenoid valve side) using a suitable rubber hose directly as shown figure. (The intake manifold vacuum will be directly applied to the EGRC-BPT valve and the EGR valve.)
(4) Start engine.
(5) Check for the EGR valve lifting with engine at less than 1,500 rpm under no load.
EGR valve should remain closed or slightly lift up.
(6) Keep engine speed at about 2,000 rpm, then check the EGR valve lifting when revving engine up to 4,000 rpm under no load.
EGR valve should lift up to the full position, and go down without sticking when the engine is returned to idle.
(7) Check rubber hose between the EGRC-solenoid valve and the collector for incorrect connection, cracks or obstruction.
For vacuum hose location, refer to 'Vacuum Hose Drawing".






DIAGNOSTIC PROCEDURE


COMPONENT INSPECTION






EGRC-BPT valve
1. Plug one of two ports of EGRC-BPT valve.
2. Vacuum from the other port and check leakage without applying any pressure from under EGRC-BPT valve. Leakage should exist.









EGRC-solenoid valve
Check solenoid valve, following the table as shown below:
If NG, replace the solenoid valve.









EGR temperature sensor
Check resistance change and resistance value.
If NG, replace EGR temperature sensor.