LEMON Manuals: Even more car manuals for everyone
Home >> Buick >> 2004 >> Century Custom >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls (DTC P0140 To P0496) >> Engine Controls Diagnosis >> DTC P0405 >> Test Description

Test Description

The number below refers to the step number on the diagnostic table.

  1. 9:  By disconnecting each component one at a time, the component that is pulling the 5-volt reference circuit low will be revealed.
DTC P0405

Step Action Values Yes No
Schematic Reference:  Engine Controls Schematics 
Connector End View Reference:  Engine Controls Connector End Views  or  Powertrain Control Module (PCM) 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 P0641 also set? - Go to DTC P0641 Go to Step 3 
3
  1. Turn ON the ignition, with the engine OFF.
  2. Observe the EGR Position Sensor voltage parameter with a scan tool.
Is the EGR Position Sensor voltage parameter less than the specified value?		 0.35 V Go to Step 5  Go to Step 4 
4
  1. Observe the Freeze Frame/Failure Records 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 5  Go to Intermittent Conditions
5
  1. Turn OFF the ignition.
  2. Disconnect the exhaust gas recirculation (EGR) valve.
  3. Connect a 3-amp fused jumper wire between the 5-volt reference circuit of the EGR valve and the EGR valve position signal circuit.
  4. Turn ON the ignition, with the engine OFF.
  5. Observe the EGR Position Sensor parameter with a scan tool.
Is the EGR Position Sensor parameter more then the specified value?		 4.9 V Go to Step 11  Go to Step 6 
6
  1. Disconnect the 3-amp fused jumper wire.
  2. Connect a test lamp between the 5-volt reference circuit of the EGR valve and the low reference circuit of the EGR valve.
Does the test lamp illuminate?		 - Go to Step 10  Go to Step 7 
7 Test the 5-volt reference circuit of the EGR valve for an open or for high resistance. Refer to Circuit Testing andWiring Repairs in Wiring Systems.
Did you find and correct the condition?		 - Go to Step 16  Go to Step 8 
8 Test all 5-volt reference circuits for a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?		 - Go to Step 16  Go to Step 9 
9 
  1. Connect a DMM between the 5-volt reference circuit of the EGR valve and the low reference circuit of the EGR valve. Observe the voltage while disconnecting all sensors, one at a time, that use a 5-volt reference circuit. A change in voltage indicates the faulty component.
  2. Replace that component as necessary. Refer to the appropriate replacement procedure.
Did you find and correct the condition?		 - Go to Step 16  Go to Step 12 
10 Test the EGR valve position signal circuit for the following conditions:
  • A short to ground
  • An open
  • High resistance

Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?		 - Go to Step 16  Go to Step 12 
11 Test the EGR valve position signal circuit for a short to the EGR solenoid high control circuit. Refer to Circuit Testing andWiring Repairs in Wiring Systems.
Did you find and correct the condition?		 - Go to Step 16  Go to Step 13 
12 Test for an intermittent and for a poor connection at the PCM. 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 16  Go to Step 15 
13 Test for an intermittent and for a poor connection at the EGR valve. 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 16  Go to Step 14 
14 Replace the EGR valve. Refer to Exhaust Gas Recirculation (EGR) Valve Replacement .
Did you complete the replacement?		 - Go to Step 16  -
15 Replace the PCM. Refer to Powertrain Control Module (PCM) Replacement .
Did you complete the replacement?		 - Go to Step 16  -
16
  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 17 
17 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
scientia non olet · About LEMON Manuals