P0400
Exhaust Gas Recirculation (EGR) System:
Exhaust Gas Recirculation (EGR) System (continued):
Exhaust Gas Recirculation (EGR) System (continued):
Exhaust Gas Recirculation (EGR) System (continued):
Exhaust Gas Recirculation (EGR) System:
Circuit Description
The Exhaust Gas Recirculation (EGR) system controls the formation of Oxides of Nitrogen (NOx) emissions by recirculating the exhaust gases into the combustion chamber.
Conditions for Running the DTC
^ Engine coolant temperature between 80°C (175°F) and 110°C (230°F).
^ Intake air temperature between -10°C (14°F) and 50°C (122°F).
^ Barometric pressure greater than or equal to 75 kPa.
^ Engine RPM between 1400 and 4000 RPM.
^ Fuel tank level greater than 25%.
^ Vehicle speed greater than 32 km/h (20 mph).
Conditions for Setting the DTC
Intake pressure change during steady state driving conditions:
^ Throttle position change is less than 0.244° in 16 firing events.
^ After 240 seconds from engine start in EGR control mode.
^ Intake pressure difference diagnostic will run for 2 seconds, once per drive cycle.
Intake pressure change during deceleration:
^ After 290 seconds from engine start in fuel shut-off mode.
^ Intake pressure difference diagnostic will run for 1 second, once per drive cycle.
Action Taken When the DTC Sets
^ The Malfunction Indicator Lamp (MIL) will illuminate after two consecutive ignition cycles in which the diagnostic runs with the fault active.
^ The PCM will record operating conditions at the time the diagnostic fails. This information will be stored in the Freeze Frame buffer.
Conditions for Clearing the MIL/DTC
^ The MIL will turn "OFF" after three consecutively passing cycles without a fault present.
^ A History DTC will clear after 40 consecutive warm-up cycles without a fault.
^ DTC(s) can be cleared by using a scan tool or by disconnecting the PCM battery feed.
Diagnostic Aids
Normal engine operating temperature is specified as 80°C (175°F) or above.
Check The Following Conditions:
^ Vacuum hoses for poor connections, leakage, deterioration, clogged or incorrect routing.
^ EGR valve malfunction, stuck closed, stuck open, clogged.
^ EGR pressure transducer malfunction.
^ EGR solenoid vacuum valve and the EGR bypass valve and their circuitry for malfunctions.
^ Poor connection at PCM. Inspect harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, and poor terminal to wire connection.
^ Damaged harness. Inspect the wiring harness for damage.
DTC P04OO is set when the expected change in Manifold Absolute Pressure (MAP) is greater or less than the specified value, when the EGR valve is turned "ON" (opened) and then turned "OFF" (closed). Therefore any condition that can affect the accuracy of the MAP sensor readings should be investigated.
^ Retarded ignition timing.
^ Restricted exhaust system.
^ Faulty vacuum supply hose(s) to the MAP sensor. If DTC P04OO cannot be duplicated, the information included in the Freeze Frame data can be useful in determining vehicle operating conditions when the DTC was first set.
If any wiring repairs need to be made, Refer to Repair Procedures in Diagrams.
Test Description
Number(s) below refer to the step number(s) on the Diagnostic Table.
1. The Powertrain OBD System Check prompts the technician to complete some basic checks and store the freeze frame data on the scan tool if applicable. This creates an electronic copy of the data taken when the fault occurred. The information is then stored in the scan tool for later reference.
2. Checks for an EGR valve that is staying open.
3. Determine if there are faults in the EGR valve or EGR by-pass valve components. Output controls can be found on the scan tool under Misc. Tests.
4. Determine if fault is present in the EGR pressure transducer or EGR solenoid vacuum valve components. When engine is cold the EGR valve should not operate when engine rpm is raised. Bring engine to operating temperatures and raise rpm. The EGR valve should move accordingly.
5. Driving the vehicle under these conditions will verify that the fault is present. If no DTC sets the fault is intermittent.
9. Determine the cause of the incorrect flow of exhaust gas.
14. After completing the diagnostic procedures and no open or short was found in the EGR by-pass valve control circuit, replace the PCM.
22. After the complete DTC table has been followed and no open or short was found in the EGR solenoid vacuum valve control circuit and the problem still exists, replace the PCM.