P0400
TECHNICAL DESCRIPTION- When the EGR solenoid switches from "OFF" to "ON" while the engine is running, EGR gas flows.
- The ECM checks how the EGR gas flow signal changes.
DTC SET CONDITIONS
Check Conditions
- At least twenty seconds have passed since the last monitor was completed.
- Engine coolant temperature is higher than 82°C (180°F).
- Engine speed is between 1,000 and 2,000
- Intake air temperature is higher than 5°C (41°F).
- Barometric pressure is higher than 76 kPa (11 psi).
- Vehicle speed is 30 km/h (18.7 mph) or more.
- At least ninety seconds have passed since manifold differential pressure sensor output voltage fluctuated 1.5 volts or more.
- The throttle valve is closed.
- Volumetric efficiency is lower than 15
- While fuel is being shut off.
- Monitoring time: 2 seconds.
Judgement Criteria
- The intake manifold pressure fluctuations are minimal. When the EGR solenoid is turned ON.
- Three monitors during one drive cycle.
TROUBLESHOOTING HINTS
The most likely causes for this code to be set are:
- EGR valve does not open.
- EGR control vacuum is too low.
- EGR solenoid failed.
- Open or shorted EGR solenoid circuit, or loose connector.
- Manifold differential pressure sensor failed.
- ECM failed.
- PCM failed.
DIAGNOSIS
Required Special Tool:
MB991502: Scan Tool (MUT-II)
STEP 1. Check the EGR system.
Refer to Emission Control System - Exhaust Gas Recirculation (EGR) System - General Information.
If correct, go to Step 2.
If incorrect, repair or replace. Then go to Step 3.
CAUTION: To prevent damage to scan tool MB991502, always turn the ignition switch to "LOCK" (OFF) position before connecting or disconnecting scan tool MB991502.
STEP 2. Using scan tool MB991502, check data list item 95: Manifold Differential Pressure Sensor.
1. Connect scan tool MB991502 to the data link connector.
2. Start the engine and run at idle.
3. Set scan tool MB991502 to the data reading mode for item 95, Manifold Differential Pressure Sensor.
- Should be between 62 and 76 kPa at engine idling.
If not within specifications, refer to DTC P1400
- Manifold Differential Pressure Sensor Circuit Malfunction.
If within specifications, clean the EGR valve and EGR passage. Then go to Step 3.
STEP 3. Test the OBD-II drive cycle.
1. Carry out a test drive with the drive cycle pattern. Refer to Procedure 5 - Exhaust Gas Recirculation (EGR) System Monitor.
2. Read the diagnostic trouble code, and confirm that diagnostic trouble code P0400 does not reset.