P0400

SYSTEM DESCRIPTION
This system cuts and controls vacuum applied to the EGR valve to suit engine operating conditions. This cut-and-control operation is accomplished through the ECM and the EGRC-solenoid valve. When the ECM detects any of the following conditions, current flows through the solenoid valve. This causes the port vacuum to be discharged into the atmosphere. The EGR valve remains closed.
- Low engine coolant temperature
- Engine starting
- High-speed engine operation
- Engine idling
- Excessively high engine coolant temperature
- Mass air flow sensor malfunction





COMPONENT DESCRIPTION
Exhaust gas recirculation (EGR) valve
The EGR valve controls the amount of exhaust gas routed to the intake manifold. Vacuum is applied to the EGR valve in response to throttle valve opening. The vacuum controls the movement of a taper valve connected to the vacuum diaphragm in the EGR valve.





EGRC-solenoid valve
The EGRC-solenoid valve responds to signals from the ECM. When the ECM sends an ON (ground) signal, the coil in the solenoid valve is energized. A plunger will then move to cut the vacuum signal (from the throttle body to the EGR valve).
When the ECM sends an OFF signal, the vacuum signal passes through the solenoid valve. The signal then reaches the EGR valve.








ON BOARD DIAGNOSIS LOGIC
If the absence of EGR flow is detected by EGR temperature sensor under the condition that calls for EGR, a low-flow malfunction is diagnosed.

DIAGNOSTIC TROUBLE CODE CONFIRMATION PROCEDURE

CAUTION: Always drive vehicle at a safe 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.
- During the test, P0400 will not be stored in ECM even though "NG" is displayed on the CONSULT screen.

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











With Consult
(1) Turn ignition switch "ON"
(2) Check "COOLAN TEMP/S" in "DATA MONITOR" mode witch CONSULT.
Confirm COOLAN TEMP/S value is within the range listed below.
COOLANT TEMP/S: Less than 40°C (104°F)
If the value is out of range, park the vehicle in a cool place and allow the engine temperature to stabilize. Do not attempt to lower the coolant temperature with a fan or means other than ambient air. Doing so may produce an inaccurate diagnostic result.
(3) Turn ignition switch "ON" and select "EGR SYSTEM P0400" of "EGR SYSTEM" in "DTC WORK SUPPORT" mode with CONSULT.
(4) Touch "START".
(5) Start engine and let it idle. When the engine coolant temperature reaches 70°C (158°F), immediately go to the next step.
(6) Accelerate vehicle to a speed to 40 km/h (25 MPH) once and then stop vehicle.
If "COMPLETED" with "OK" appears on CONSULT screen, go to step 9).
If "COMPLETED" does not appear on CONSULT screen, go to the following step.
(7) Check the output voltage of "THRTL POS SEN" (at closed throttle position) and note it.
(8) When the following conditions are met, "TESTING" will be displayed on the CONSULT screen. Maintain the conditions until "TESTING" changes to "COMPLETED". (It will take approximately 30 seconds or more.)
CMPS-RPM (REF): 2,000 - 3,000 rpm (A/T)
1,800 - 3,000 rpm (M/T)
Vehicle speed: 10 km/h (6 MPH) or more B/FUEL SCHDL: 2.5 - 4 ms
THRTL POS SEN: (X + 0.38) - (X + 0.70) V
X = Voltage value measured at step 7)
Selector lever: Suitable position
If "TESTING" is not displayed after 5 minutes, retry from step 2).
(9) Make sure that "OK" is displayed after touching "SELFDIAG RESULTS". If "NG" is displayed, refer to "DIAGNOSTIC PROCEDURE".

OVERALL FUNCTION CHECK
Use this procedure to check the overall EGR function. During this check, a 1st trip DTC might not be confirmed.

Without Consult
(1) Lift up drive wheels.
(2) Start engine and warm it up to normal operating temperature.





(3) Check the EGR valve lifting when revving engine from 2,000 rpm up to 4,000 rpm in 1st shift position.
EGR valve should 11ff up and down without sticking.








- Disconnect harness connectors (F17) and (F71).
(The DTC for EGRC-solenoid valve will be displayed, however, ignore it.)
If NG, go to (A) in DIAGNOSTIC PROCEDURE.





(4) Check voltage between harness connector (F23) terminal (2) and ground at idle speed.
Less than 4.5V should exist.
(5) Turn ignition switch "OFF".
(6) Disconnect harness connectors (F23), (F50) and ECM harness connector.





(7) Check harness continuity between harness connector (F23) terminal (7) and ECM terminal (50).
Continuity should exist.
(8) Perform "COMPONENT INSPECTION", "EGR temperature sensor".








DIAGNOSTIC PROCEDURE





WIRING DIAGRAM

COMPONENT INSPECTION
EGR Valve





- Apply vacuum to EGR vacuum port with a hand vacuum pump. EGR valve spring should lift.
- Check for sticking.
If NG, repair or replace EGR valve.

EGRC-Solenoid Valve








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

EGR Temperature Sensor











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





EGRC-BPT Valve
1. Plug one of two ports of EGRC-BPT valve.
2. Vacuum from the other port and check for leakage while applying a pressure above 0.981 kPa (100 mmH2O, 3.94 inH2O) from under EGRC-BPT valve.
3. If a leakage is noted, replace the valve.