GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Cadillac 🢒 2003 🢒 Seville 🢒 Engine 🢒 Engine Controls - 4.6L 🢒 DTC P0403

Circuit Description

The powertrain control module (PCM) controls the exhaust gas recirculation (EGR) valve with a solid state device called a driver. The driver supplies the EGR solenoid with 12 volts that is pulse width modulated (PWM) through the EGR solenoid high control circuit. A ground path is provided by the PCM through the EGR solenoid low control circuit. The driver has the ability to detect an electrical malfunction on the EGR solenoid control circuits. If the PCM determines that the driver has detected an electrical malfunction on one of these circuits, DTC P0403 sets.

Conditions for Running the DTC

The engine is cranking or running.

The Ignition 1 Signal parameter is between 11-18 volts.

Conditions for Setting the DTC
    • The PCM detects an electrical malfunction in the EGR solenoid high control circuit or the EGR solenoid low control circuit.
    • The above condition is met for more than 10 seconds.

Action Taken When the DTC Sets
    • The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
    • The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

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

  1. This step tests for voltage that is constantly being applied to the EGR valve.

Step

Action

Yes

No

Schematic Reference: Engine Controls Schematics

Connector End View Reference: Powertrain Control Module 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. Turn ON the ignition, with the engine OFF.
  2. Command the EGR from 0 percent to 100 percent with a scan tool.

Does the EGR Position Sensor parameter remain with in 3 percent of the Desired EGR Position parameter when commanded with a scan tool?

Go to Step 3

Go to Step 4

3
  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 4

Go to Intermittent Conditions

4
  1. Turn OFF the ignition.
  2. Disconnect the EGR valve.
  3. Turn ON the ignition, with the engine OFF.
  4. Probe the EGR solenoid high control circuit with a test lamp that is connected to a good ground.
  5. Command the EGR valve from 0-10 percent and from 10-0 percent with a scan tool.

Does the test lamp turn ON at 10 percent and OFF at 0 percent when commanded with a scan tool?

Go to Step 5

Go to Step 6

5
  1. Connect a test lamp between the EGR solenoid high control circuit and the EGR solenoid low control circuit.
  2. Command the EGR valve from 0-10 percent with a scan tool.

Does the test lamp illuminate?

Go to Step 10

Go to Step 9

6

Does the test lamp remain illuminated when the EGR valve is commanded to 0 percent with a scan tool?

Go to Step 8

Go to Step 7

7

Test the EGR solenoid high control circuit for a short to ground or for 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 for 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

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 14

Go to Step 12

11

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 14

Go to Step 13

12

Replace the EGR valve. 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. 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 15

15

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