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DTC Troubleshooting

DIAGNOSIS PROCEDURE - DTC P0400 EXHAUST GAS RECIRCULATION (EGR) FLOW MALFUNCTION

Step Action Value(s) Yes No
1 Perform an On-Board Diagnostic (OBD) System Check.
Is the system check complete?		 - Go to Step 2. Go to "ON-BOARD DIAGNOSTIC (OBD II) SYSTEM CHECK ".
2
  1. Turn the ignition switch to LOCK.
  2. Install the scan tool.
  3. Command the exhaust gas recirculation (EGR) valve to the specified values.

Does the Actual EGR Position follow the desired EGR position?		 25%, 50% 75%, 100% Go to Step 19. Go to Step 3.
3
  1. Turn the ignition switch to ON.
  2. Disconnect the EGR valve electrical connector.
  3. With a test light connected to B+, probe the ground circuit to the EGR valve.

Does the test light illuminate?		 - Go to Step 4. Go to Step 5.
4
  1. Connect the test light to ground.
  2. Probe the EGR control circuit at terminal 3 to the EGR valve.
  3. Command the EGR valve to the specified values using a scan tool.

After the command is raised, does the test light glow brighter, flash or maintain a steady glow?		 25%, 50% 75%, 100% Go to Step 6. Go to Step 7.
5 Repair the open or poor connection in the EGR ground circuit.
Is the repair complete?		 - Go to Step 19. -
6 With a test light still connected to ground, probe the signal circuit at terminal 3.
Does the test light illuminate?		 - Go to Step 8. Go to Step 9.
7 With a test light still connected to ground, again probe the signal circuit without commanding the EGR valve with the scan tool.
Does the test light illuminate?		 - Go to Step 10. Go to Step 11.
8 Check the signal circuit for a short to voltage and repair as necessary.
Is a repair necessary?		 - Go to Step 19. Go to Step 12.
9 With a digital voltmeter (DVM) connected to ground, probe the 5 V reference circuit at terminal 4.
Is the voltage measured near the specified value?		 5V Go to Step 13. Go to Step 14.
10 Check the control circuit for a short to battery voltage and repair as necessary.
Is a repair necessary?		 - Go to Step 19. Go to Step 12.
11 Connect the test light to B+ and again probe the control circuit at terminal 5.
Does the test light illuminate?		 - Go to Step 15. Go to Step 16.
12 Replace the engine control module (ECM).
Is the replacement complete?		 - Go to Step 19. -
13 Check the EGR ground circuit for a poor connection or proper terminal tension at the ECM and repair as necessary.
Is a repair necessary?		 - Go to Step 19. Go to Step 17.
14 Check the 5 V reference circuit for a shortage to battery voltage and repair as necessary.
Is a repair necessary?		 - Go to Step 19. Go to Step 12.
15 Check the control circuit for a shortage to ground and repair as necessary.
Is a repair necessary?		 - Go to Step 19. Go to Step 12.
16 Check the control circuit for an open or poor connection at the EGR valve electrical connector and repair as necessary.
Is a repair necessary?		 - Go to Step 19. Go to Step 18.
17 Replace the EGR valve.
Is the replacement complete?		 - Go to Step 19. -
18 Check the ECM electrical connector for a poor connection and repair as necessary.
Is a repair necessary?		 - Go to Step 19. Go to Step 12.
19
  1. Using the scan tool, clear the Diagnostic Trouble Codes (DTCs).
  2. Start the engine and idle at normal operating temperature.
  3. Operate the vehicle within the conditions for setting the DTC as specific in the supporting text.

Does the scan tool indicate that this diagnostic ran and passed?		 - Go to Step 20. Go to Step 2.
20 Check if any additional DTCs are set.
Are any DTCs displayed that have not been diagnosed?		 - Go to applicable DTC TABLE . System OK
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