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Home >> GMC >> 2003 >> Safari Van Cargo, AWD >> Repair and Diagnosis >> External Pages >> Different car >> Section 1044 (Engine Controls Diagnosis - 6.6L (Lb7) (DTCS P0237 To P0611)) >> Diagnosis >> DTC P0406 >> 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. 2:  If DTC P0651 sets, there is a short to voltage on the 5-volt reference circuit. Perform the DTC P0651 diagnostic before proceeding.
DTC P0406

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  Is DTC P0651 also set? - Go to DTC P0651 Go to Step 3 
3
  1. Start the engine.
  2. Command the EGR Solenoid to 100 % with a scan tool.
  3. Observe the EGR Vacuum Sensor parameter with a scan tool.
Is the EGR Vacuum Sensor parameter more than the specified value?		 158 kPa Go to Step 4  Go to Intermittent Conditions
4
  1. Turn OFF the ignition.
  2. Disconnect the EGR vacuum sensor harness connector.
  3. Turn ON the ignition, with the engine OFF.
  4. Connect a test lamp between the low reference circuit of the EGR vacuum sensor and B+.
Does the test lamp illuminate?		 - Go to Step 6  Go to Step 5 
5 Test the low reference circuit of the EGR vacuum sensor for high resistance or an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?		 - Go to Step 13  Go to Step 7 
6
  1. Disconnect the EGR vacuum sensor harness connector.
  2. With a scan tool, observe the EGR vacuum sensor parameter.
Does the scan tool indicate that the EGR Vacuum Sensor parameter is less than the specified value?		 18 kPa Go to Step 8  Go to Step 7 
7 Test the signal circuit of the EGR vacuum sensor for a short to voltage. Refer to Testing for a Short to Voltage and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?		 - Go to Step 12  Go to Step 9 
8 Test for an intermittent and for a poor connection at the EGR vacuum sensor. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.
Did you find and correct the condition?		 - Go to Step 12  Go to Step 10 
9 Test for an intermittent and for a poor connection at the ECM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.
Did you find and correct the condition?		 - Go to Step 12  Go to Step 11 
10 Replace the EGR vacuum sensor. Refer to Exhaust Gas Recirculation (EGR) Valve Vacuum Sensor Replacement .
Did you complete the replacement?		 - Go to Step 12  -
11 Replace the ECM. Refer to Engine Control Module (ECM) Replacement .
Did you complete the replacement?		 - Go to Step 12  -
12
  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 13 
13 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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