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Home >> GMC >> 2003 >> Safari Van Cargo, AWD >> Repair and Diagnosis >> External Pages >> Different car >> Section 1569 (Engine Controls And Fuel - 3.5L (L66) - DTC P0223 To DTC P0499) >> DTC P0401 >> Test Description

Test Description

WARNING: This page is about a different car, the 2007 Saturn Vue. However, it is still accessible from the selected car via links, so may be relevant.

The numbers below refer to the step numbers on the diagnostic table.

  1. 2:  This step tests the physical movement of the EGR valve. Normal EGR position voltage at the full open position is 3.10-3.20 volts.
  2. 4:  Exhaust system leaks can cause an insufficient amount of EGR flow through the EGR valve. This condition can cause a less than expected MAP changes due to insufficient exhaust back pressure. Possible causes of this could be a leaking exhaust system, a leaking EGR pipe, or non OEM exhaust parts.
  3. 5:  Intake system leaks can affect exhaust gas flow into the intake manifold from the EGR valve. This condition can cause a less than expected MAP change causing the DTC P0401 diagnostic to fail.
DTC P0401

Step Action Values Yes No
1 Did you perform the Diagnostic System Check - Vehicle? - Go to Step 2  Go to Diagnostic System Check - Vehicle
2 
  1. Start the engine.
  2. Run the engine until the engine coolant temperature is at least 85°C (185°F).
  3. With the scan tool, command the EGR valve from 0 to 100 percent while observing the EGR Sensor data parameter. Refer to Scan Tool Output Controls .
Was the EGR sensor voltage more than the specified value when at 100 percent?		 3.10 V Go to Step 3  Go to Step 7 
3
  1. Observe the Freeze Frame/Failure Records data for this DTC.
  2. Turn OFF the ignition for 30 seconds.
  3. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records.
Did the DTC fail this ignition?		 - Go to Step 4  Go to Diagnostic Aids In This Test
4  Inspect the exhaust system for leaks, restrictions, and for modification of original equipment manufacture (OEM) parts.
Did you find and correct the condition?		 - Go to Step 8  Go to Step 5 
5  Inspect for a vacuum leak between the exhaust gas recirculation (EGR) valve and the intake manifold.
Did you find and correct the condition?		 - Go to Step 8  Go to Step 6 
6
  1. Remove the EGR valve. Refer to Exhaust Gas Recirculation Valve Replacement .
  2. Inspect for any of the following conditions:
    • Inspect the EGR valve pintle and the EGR valve passages for leaks or for restrictions.
    • Inspect the exhaust gas passages for excessive carbon deposits and restrictions or blockage.
    • Inspect the intake manifold passages for restrictions and blockage.
    • Clean and remove any deposits, restrictions, or blockage as necessary.
Did you find and correct a condition?		 - Go to Step 8  Go to Step 7 
7 Replace the EGR valve. Refer to Exhaust Gas Recirculation Valve Replacement .
Did you complete the replacement?		 - Go to Step 8  -
8
  1. Clear the DTCs with a scan tool.
  2. Turn OFF the ignition for 30 seconds.
  3. Start the engine.
  4. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records.
Did the DTC fail this ignition?		 - Go to Step 2  Go to Step 9 
9 Observe the Capture Info with a scan tool.
Are there any DTCs that have not been diagnosed?		 - Go to Diagnostic Trouble Code (DTC) List - Vehicle System OK
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