GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Buick 🢒 2002 🢒 LeSabre 🢒 DTC 🢒 DTC P0403

Circuit Description

The powertrain control module (PCM) monitors the exhaust gas recirculation (EGR) valve pintle position input to ensure that the valve responds properly to commands from the PCM. The linear EGR valve is controlled by using an ignition positive driver and ground circuit within the PCM. The driver has the ability to detect an electrical malfunction in the ignition positive or ground circuit. If an electrical malfunction occurs, the driver signals the PCM to set this DTC.

Conditions for Running the DTC

The engine is cranking or running.

The system voltage is between 10-16 volts.

Conditions for Setting the DTC
    • The PCM detects an electrical malfunction in the control circuit for the EGR valve.
    • The condition is present for more than 20 seconds.

Action Taken When the DTC Sets
    • The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle in which the diagnostic runs and fails.
    • The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Freeze Frame/Failure Records.
    • The PCM disables the EGR valve for the ignition cycle.

Conditions for Clearing the MIL/DTC
    • The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
    • A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
    • A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
    • Clear the MIL and the DTC with a scan tool.

Test Description

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

  1. When you use the scan tool to increment the EGR valve, increment the valve to 10 percent then to 0 percent . Repeat this process to see if the test lamp turns ON then OFF. If the test lamp stays ON after commanded to 0 percent the EGR solenoid high control circuit is shorted to voltage.

    2.

  2. This step tests for an open in the ground circuit to the solenoid.

    3.

  3. This step tests if voltage is constantly being applied to the solenoid.

Step

Action

Yes

No

Schematic Reference: Engine Controls Schematics

1

Did you perform the Diagnostic System Check-Engine Controls?

Go to Step 2

Go to Diagnostic System Check - Engine Controls

2
  1. Install a scan tool.
  2. Turn ON the ignition, with the engine OFF.
  3. Use a scan tool in order to command the EGR from 0 percent to 100 percent.

Does the EGR position sensor remain close to the Desired EGR Position at all Commanded positions?

Go to Step 3

Go to Step 4

3
  1. Observe the Freeze Frame and/or 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 as specified in the supporting text or as close the Freeze Frame and/or Failure Records data that you observe.

Does the DTC fail this ignition?

Go to Step 4

Go to Intermittent Conditions

4

  1. Turn OFF the ignition.
  2. Disconnect the EGR.
  3. Turn ON the ignition, with the engine OFF.
  4. Probe the EGR solenoid high control circuit with a test lamp connected to a good ground.
  5. Use a scan tool in order to command the EGR between 0 percent and 10 percent.

Does the test lamp turn ON and OFF with each command?

Go to Step 5

Go to Step 6

5

  1. Connect a test lamp between the high control circuit of the solenoid and the low control circuit of the solenoid.
  2. Use a scan tool in order to command the EGR between 0 percent and 10 percent.

Does the test lamp turn ON and OFF with each command?

Go to Step 10

Go to Step 9

6

Does the test lamp remain illuminated with each command?

Go to Step 8

Go to Step 7

7

Test the EGR Solenoid high control circuit for a short to ground or an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 14

Go to Step 11

8

Test the EGR solenoid high control circuit for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 14

Go to Step 11

9

Test the EGR solenoid low control circuit for an open or high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 14

Go to Step 11

10

Inspect for poor connections at the harness connector of the EGR. 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 14

Go to Step 12

11

Inspect for poor connections at the harness connector of 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 14

Go to Step 13

12

Replace the EGR. Refer to Exhaust Gas Recirculation Valve Replacement .

Did you complete the replacement?

Go to Step 14

--

13

Replace the PCM. Refer to Powertrain Control Module Replacement .

Did you complete the replacement?

Go to Step 14

--

14
  1. Use the scan tool in order to clear the DTCs.
  2. Turn OFF the ignition for 30 seconds.
  3. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.

Does the DTC run and pass?

Go to Step 15

Go to Step 2

15

Use a scan tool, in order to observe the stored information, Capture Info.

Does the scan tool display any DTCs that you have not diagnosed?

Go to Diagnostic Trouble Code (DTC) List

System OK