GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Cadillac 🢒 2002 🢒 DeVille 🢒 Engine 🢒 Engine Controls - 4.6L 🢒 DTC P0404

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 PCM compares the EGR position sensor with desired EGR position when the valve is commanded open. If the difference between the EGR position sensor and Desired EGR Position is more than 8 percent the diagnostic trouble code (DTC) P0404 will set.

Conditions for Running the DTC
    • The ignition voltage is greater than 11 volts.
    • The EGR is enabled.

Conditions for Setting the DTC
    • The difference between the EGR position sensor and the desired EGR position is more than 8 percent.
    •  The condition is present 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.

Diagnostic Aids

Inspect for the following condition:

    •  Excessive deposits on the EGR pintle or seat--Remove the EGR valve and inspect for deposits that may interfere with the EGR valve pintle extending completely or cause the pintle to stick.
    • If the problem is intermittent, refer to Intermittent Conditions .

Test Description

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

  1. This step verifies that the malfunction is present.

    2.

  2. If DTC P0404 will only set under certain conditions, the malfunction may be intermittent. Refer to Diagnostic Aids. If an intermittent wiring problem is not present, test for a faulty connection at the PCM or the EGR valve. If the connections are OK and the DTC P0404 continues to set, replace the EGR valve.

  3. When using 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 does not turn ON the EGR solenoid high control circuit is open or shorted to ground.

Step

Action

Values

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

Important: If any of the following DTCs are set, diagnose the other DTC first.

   • Refer to DTC P0403
   • Refer to DTC P0405

  1. Connect a scan tool.
  2. Turn ON the ignition.
  3. With a scan tool, command the EGR valve from 0 percent to 100 percent.

Does the EGR position sensor remain within 8 percent of the desired EGR position at all commanded positions?

--

Go to Step 3

Go to Step 4

3

  1. Observe the Freeze Frame/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 to the Freeze Frame/Failure Records data that you observed.

Does the DTC fail this ignition?

--

Go to Step 4

Go to Diagnostic Aids

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. With a scan tool, 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 13

5
  1. Turn OFF the ignition.
  2. Turn ON the ignition, with the engine OFF.
  3. With a scan tool, observe the EGR position sensor parameter.

Does the scan tool indicate that the EGR Position Sensor is at the specified value?

0 %

Go to Step 6

Go to Step 9

6

Measure the voltage from the 5-volt reference circuit of the EGR position sensor to the low reference circuit of the EGR position sensor.

Does the DMM display voltage near the specified value?

5 V

Go to Step 7

Go to Step 8

7

Important: : If the fuse blows, locate and repair a short to ground in the signal circuit. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Connect a fused jumper between the 5-volt reference circuit of the EGR position sensor and the EGR valve position signal circuit of the EGR position sensor.

Does the scan tool indicate that the EGR position sensor is near the specified value?

100 %

Go to Step 14

Go to Step 11

8

Measure the voltage from the 5-volt reference circuit of the EGR position sensor to a good ground.

Does the DMM display voltage near the specified value?

5 V

Go to Step 10

Go to Step 12

9

Test the EGR Valve Position Signal 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 18

Go to Step 15

10

Test the low reference 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 18

Go to Step 15

11

Test the EGR valve position signal circuit for high resistance or a high resistance short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 18

Go to Step 16

12

Test the 5-volt reference circuit of the EGR position sensor for an open, a short to ground, or a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 18

Go to Step 16

13

Test the EGR solenoid high control circuit 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 18

Go to Step 15

14

Inspect for poor connections at the harness connector of the EGR valve. Refer to Testing for Intermittent Conditions and Poor Connections and Repairing Connector Terminals in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 18

Go to Step 16

15

Inspect for poor connections at the harness connector of the PCM. Refer to Testing for Intermittent Conditions and Poor Connections and Repairing Connector Terminals in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 18

Go to Step 17

16

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

Did you complete the replacement?

--

Go to Step 18

--

17

Replace the PCM. Refer to Powertrain Control Module Replacement .

Did you complete the replacement?

--

Go to Step 18

--

18
  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 19

Go to Step 2

19

With a scan tool, 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