P0402

P0402-EGR FLOW EXCESSIVE DETECTED





For a complete wiring diagram Refer to Diagrams/Electrical.

Theory of Operation


The purpose of this diagnostic is to check for a condition where EGR flow is higher than commanded. This algorithm runs at idle. The diagnostic closes the EGR valve, and limits the intake air throttle valve. It then looks at fresh air flow fraction and the difference in pressure between the exhaust manifold pressure sensor and boost pressure sensor to determine if the EGR valve is leaking. The ECM will illuminate the MIL lamp after the diagnostic runs and fails in two consecutive drive cycles. The ECM will also illuminate the ETC lamp. The MIL lamp will turn off once the diagnostic runs and passes in 4 consecutive drive cycles.

- When Monitored:
Engine running, Coolant temperature above a calibrated threshold, Intake Manifold temperature above a calibrated threshold, EGR valve is closed.

- Set Condition:
When intake throttle is closed, EGR fraction increases more than a calibrated threshold.







Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. Initial Inspection and Diagnostic Overview


Diagnostic Test


1. OTHER DTC'S
Ignition on, engine not running.
With the scan tool, read DTC's.
Are there any other DTCs present?

Yes


- Repair all other DTC's first.


No


- Go To 2



2. THERMOSTAT OUTLET
Remove the exhaust gas pressure sensor from the thermostat outlet.
Is the outlet free of debris?

Yes


- Go To 3


No


- Remove debris from outlet.
- Go To 3



3. EXHAUST GAS PRESSURE SENSOR TUBE
Remove the steel tube from the exhaust manifold to the exhaust pressure sensor port.
Is the tube free from debris?

Yes


- Go To 4


No


- Clean the tube and reinstall.
- Go To 4



4. EGR AIRFLOW THROTTLE CONTROL VALVE
Remove the boot from the EGR airflow throttle control valve. Using a mirror, look at the butterfly valve on the inside of the EGR airflow throttle control valve.
Start the vehicle, let idle for 10 seconds and key off.

NOTE: If functioning properly the EGR airflow throttle control valve will cycle closed immediately after the engine is shut down.

Did the EGR airflow throttle control valve cycle closed immediately after the engine was shut down?

Yes


- Go To 5


No


- Replace the EGR airflow throttle control valve.
- Perform POWERTRAIN VERIFICATION TEST (DIESEL). Powertrain Verification Test



5. P0402 ACTIVE
Ignition on, engine not running.
With the scan tool, read DTC's.
Is P0402 still active?

Yes


- Replace EGR Valve.
- Perform POWERTRAIN VERIFICATION TEST (DIESEL). Powertrain Verification Test


No


- Repair complete.
- Perform POWERTRAIN VERIFICATION TEST (DIESEL). Powertrain Verification Test