Exhaust Gas Recirculation: Testing and Inspection

EGR System Diagnosis




Circuit Description
In order to control the exhaust gas recirculation (EGR), the control module operates the linear EGR valve The linear EGR valve is a small motor with a pintle that is normally closed. By providing a ground path, the control module will open the pintle and allow the exhaust gasses to pass through the valve. The control module of the EGR is based on the following inputs:
- The engine coolant temperature -above 25° C.
- The TP OFF idle
- MAP
- BARO
- Park/Neutral position
- The pintle position sensor.

If DTC P0401 or P1406 is stored, refer to the applicable DTC table. This chart is used for a malfunctioning valve, plugged EGR passages, or improper wiring connections.
An intermittent may be caused by any of the following conditions:
- A poor connection
- Rubbed through wire insulation
- A broken wire inside the insulation

Thoroughly check any circuitry that is suspected of causing the intermittent complaint. Refer to Testing for Intermittent and Poor Connections.

If a repair is necessary, refer to Wiring Repairs or Connector Repairs.

Steps 1 - 5:

Steps 6 - 10:

Steps 11 - 15:

Steps 16 - 22:

Steps 23 - 24:

Test Description
The numbers below refer to the step numbers in the diagnostic table.
2. At idle, the EGR valve should not be open more than 0 percent.
3. This step checks the ability of the pintle to be manually commanded to the desired positions.
5. This step checks the electrical circuit for a short to voltage.
6. This step checks the electrical control circuits from the VCM to the EGR valve.