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Home >> GMC >> 2003 >> Safari Van Cargo, AWD >> Repair and Diagnosis >> External Pages >> Different car >> Section 996 (Engine Controls Diagnosis - 6.6L (Lb7) (DTCS P0612 To P2141)) >> Diagnosis >> DTC P1404 >> Test Description

Test Description

WARNING: This page is about a different car, the 2004 GMC Sierra, 2004 GMC Cab & Chassis Sierra, 2004 Chevrolet Silverado, and 2004 Chevrolet Cab & Chassis Silverado. 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. 3:  The EGR vacuum vent solenoid is normally closed. When the EGR vacuum vent solenoid is closed, it will vent to atmosphere. Therefore it should not hold vacuum with this test.
  2. 4:  The EGR valve vacuum control solenoid is normally closed. When vacuum is applied to the commanded open EGR vacuum vent solenoid it should hold vacuum. If the vacuum does not hold, then a stuck open EGR valve vacuum control solenoid is indicated.
DTC P1404

Step Action Value(s) Yes No
Schematic Reference:  Engine Controls Schematics 
Connector End View Reference:  Engine Control Module (ECM) Connector End Views  or  Engine Controls Connector End Views 
1 Did you perform the Diagnostic System Check-Engine Controls? - Go to Step 2  Go to Diagnostic System Check - Engine Controls
2
  1. Observe the Freeze Frame/Failure Records for this DTC.
  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 3  Go To Diagnostic Aids
3 
IMPORTANT: Mark all disconnected vacuum hoses for proper installation if necessary.
  1. Turn OFF the ignition.
  2. Disconnect the vacuum hose from the EGR vacuum vent solenoid outlet port to the EGR vacuum sensor.
  3. Install a hand held vacuum pump on the outlet port of the EGR vacuum vent solenoid.
  4. Apply 15 inches of vacuum.
Does the vacuum hold steady?		 - Go to Step 7  Go to Step 4 
4 
IMPORTANT: Mark all disconnected vacuum hoses for proper installation if necessary.
  1. Disconnect the vacuum hose from the EGR vacuum vent solenoid inlet port.
  2. Install a vacuum gage on the inlet port of the EGR vacuum vent solenoid.
  3. Apply 15 inches of vacuum. The solenoid should hold vacuum.
  4. Command the EGR Vent ON with a scan tool. The EGR vacuum vent solenoid should release the vacuum to 0 inches.
Does the EGR vacuum vent solenoid operate as described in the above test?		 - Go to Step 5  Go to Step 9 
5
  1. Exit the Output Control Function on the scan tool.
  2. Compare the EGR Vacuum Sensor parameter to the BARO parameter with a scan tool.
Is the EGR Vacuum Sensor parameter within the specified value of the BARO parameter?		 +/- 4 kPa Go to Step 6  Go to Step 8 
6 Inspect for the following conditions:
Did you find and correct the condition?		 - Go to Step 10  Go to Diagnostic Aids
7 Replace the EGR vacuum vent solenoid. Refer to Exhaust Gas Recirculation (EGR) Valve Vent Solenoid Replacement .
Did you complete the replacement?		 - Go to Step 9  -
8 Replace the EGR vacuum sensor. Refer to Exhaust Gas Recirculation (EGR) Valve Vacuum Sensor Replacement .
Did you complete the replacement?		 - Go to Step 10  -
9 Replace the EGR valve vacuum control solenoid.
Did you complete the replacement?		 - Go to Step 10  -
10
  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 11 
11 Observe the Capture Info with a scan tool.
Are there any DTCs that have not been diagnosed?		 - Go to Diagnostic Trouble Code (DTC) List System OK
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