P0400

DTC P0400 - EXHAUST GAS RECIRCULATION FLOW

OUTLINE OF DIAGNOSIS
Detect the malfunction of EGR system.
Intake manifold pressure (negative pressure) is stable because the throttle valve is fully closed during the fuel shut-off in deceleration. In this case, the intake manifold pressure changes when EGR valve is opened or closed. Judge EGR system is OK or NG according to intake manifold pressure change amount.




COMPONENT DESCRIPTION




ENABLE CONDITION

GENERAL DRIVING CYCLE
Perform the diagnosis only once at the fuel shut-off in deceleration in vehicle speed 49 km/h (approx. 30 MPH). Pay attention to vehicle speed and engine speed. (The diagnosis is not completed if vehicle speed and engine speed are out of condition due to deceleration.)

DIAGNOSTIC METHOD




Measure the pressure in the following procedures when the enable conditions are completed, and then diagnosis by calculating the result.
1. PMOF1 is equal to the intake manifold pressure at enable condition completed, and EGR target step is set to 40 steps (almost fully opened).
2. PMON is equal to the intake manifold pressure in 1 second after EGR target step is set 40 steps (when enable conditions are completed), and EGR target step is set to 0 step.
3. PMOF2 is equal to the intake manifold pressure in 1 second after EGR target step is set to 0 step (in 2 seconds after enable conditions are completed).




4. Calculate the judged value using the following formula.
Judged value = [PMON - (PMOF1 + PMOF2)/2]
Judge NG when the malfunction criteria bellows are completed. Judge OK and clear NG when the malfunction criteria are not completed.

DTC CLEAR CONDITION
- When the OK idling cycle was completed 40 times in a row
- When "Clear Memory" was performed

MALFUNCTION INDICATOR LIGHT CLEAR CONDITION
- When the OK driving cycle was completed 3 times in a row
- When "Clear Memory" was performed

FAIL SAFE
- Decrease compensation when operating EGR operate
- Front O2 (A/F) sensor main learning compensation
- Calculation of basic advance ignition timing
- Knock learning compensation
- ISC control
- EGR control

ECM OPERATION AT DTC SETTING
- Memorize the freeze frame data. (For test mode $02)
- Memorize the diagnosis value and trouble standard value. (For test mode $06)