GM Service Manual Online
For 1990-2009 cars only

Circuit Description

The engine control module (ECM) monitors the position of the exhaust gas recirculation (EGR) valve through the EGR valve position sensor. The EGR valve position sensor sends a feedback voltage on the signal circuit to the ECM. This voltage varies depending on the position of the EGR valve. The ECM interprets this voltage as the position of the EGR valve. If the ECM detects a difference between the actual EGR position and the commanded EGR position, DTC P0404 sets.

DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC P0404 Exhaust Gas Recirculation (EGR) Open Position Performance

Conditions for Running the DTC

    • DTCs P0107, P0108, P0112, P0113, P0117, P0118, P0122, P0123, P0131, P0300, P0335, P0336, P0341, and P0342 are not set.
    • The EGR flow test is ran in decel fuel cut-off (DFCO) mode with the following conditions present before deceleration occurs:
       - The engine is operating in closed loop.
       - The ignition 1 voltage is between 11-16 volts.
       - The intake air temperature (IAT) is more than 15°C (59°F).
       - The engine coolant temperature (ECT) is more than 60°C (140°F).
       - The manifold absolute pressure (MAP) is greater than 75 kPa (11 psi).
       - The mass airflow (MAF) is between 71-174 mg/tdc.
       - The A/C compressor clutch does not change state during deceleration.
       - The engine speed is between 1,950-2,600 RPM.
       - The EGR is greater than 10 percent.
    • The DTC runs once an ignition cycle when the above conditions are met.

Conditions for Setting the DTC

The ECM detects a difference between the actual EGR position and the commanded EGR position.

Action Taken When the DTC Sets

    • The malfunction indicator lamp (MIL) will illuminate after 3 consecutive trips with a fail.
    • The ECM will record operating conditions at the time the diagnostic fails. This information will be stored in the Freeze Frame and Failure Records buffers.

Conditions for Clearing the MIL/DTC

    • The MIL will turn OFF after 4 consecutive ignition cycles in which the diagnostic runs without a fault.
    • DTCs can be cleared by using the scan tool.
    • Disconnect the ECM battery feed for more than 10 seconds.

Diagnostic Aids

Due to moisture associated with exhaust systems, the EGR valve may freeze and stick in cold weather at times. After the vehicle is brought into a warm shop for repairs, the valve warms and the condition disappears. By watching the actual EGR and desired EGR positions on a cold vehicle with a scan tool, the fault can be easily verified. Check the Freeze Frame data to determine if the DTC set when the vehicle was cold by viewing the engine coolant temperature (ECT).

Step

Action

Values

Yes

No

Schematic Reference: Engine Controls Schematics

Connector End View Reference: Engine 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

Is DTC P0405, P0406, or P1403 also set?

--

Go to Diagnostic Trouble Code (DTC) List

Go to Step 3

3

  1. Turn ON the ignition, with the engine OFF.
  2. Observe the EGR Position Sensor parameter with a scan tool.

Is the voltage less than the specified value?

0.80 V

Go to Step 4

Go to Step 6

4

  1. Command the EGR valve from 0 percent to 100 percent with a scan tool.
  2. Observe the EGR Position Sensor parameter with a scan tool.

Is the voltage more than the specified value?

3.70 V

Go to Step 5

Go to Step 6

5

  1. Turn OFF the ignition for 30 seconds.
  2. Operate the vehicle within the Conditions for Running the DTC.

Did the DTC fail this ignition?

--

Go to Step 6

Go to Intermittent Conditions

6

  1. Turn OFF the ignition.
  2. Disconnect the exhaust gas recirculation (EGR) valve.
  3. Turn ON the ignition, with the engine OFF.
  4. Important: Use a Test Lamp that measures between 25-30 ohms for this test.

  5. Connect a test lamp between the 5-volt reference circuit and the low reference circuit of the EGR valve position sensor.

Does the test lamp illuminate?

--

Go to Step 8

Go to Step 7

7

Connect a test lamp between the 5-volt reference circuit of the EGR valve position sensor and a good ground.

Does the test lamp illuminate?

--

Go to Step 13

Go to Step 12

8

  1. Connect a 3-ampere fused jumper wire between the signal circuit and the low reference circuit of the EGR valve position sensor.
  2. Observe the EGR Position Sensor parameter on the scan tool.

Is the parameter less than the specified value?

0.05 V

Go to Step 9

Go to Step 11

9

  1. Turn OFF the ignition.
  2. Disconnect the fuse that supplies ignition 1 voltage to the EGR valve.
  3. Measure the resistance of the ignition 1 voltage circuit of the EGR valve from the fuse terminal to the harness connector terminal of the EGR valve.

Is the resistance less than the specified value?

3 ohms

Go to Step 10

Go to Step 17

10

  1. Turn ON the ignition, with the engine OFF.
  2. Probe the control circuit of the EGR valve with a test lamp connected to battery positive voltage.
  3. Command the EGR valve to 100 percent.
  4. Measure the voltage from the probe of the test lamp to a good ground.

Is the voltage less than the specified value?

0.3 V

Go to Step 15

Go to Step 14

11

Test the signal circuit of the EGR valve position sensor 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 20

Go to Step 16

12

Test the 5-volt reference circuit of the EGR valve position sensor 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 20

Go to Step 16

13

Test the low reference circuit of the EGR valve position sensor 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 20

Go to Step 16

14

Test the control circuit of the EGR valve 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 20

Go to Step 16

15

Test the EGR valve for the following:

    • Excessive deposits on the EGR valve pintle that may interfere with the EGR valve pintle extending completely or cause the pintle to stick.
    • An intermittent and poor connection at 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 20

Go to Step 18

16

Test for an intermittent and for a poor connection at the engine control module (ECM). 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 20

Go to Step 19

17

Repair the high resistance in the ignition 1 voltage circuit of the EGR valve. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

--

Go to Step 20

--

18

Replace the EGR valve.

Did you complete the replacement?

--

Go to Step 20

--

19

Replace the ECM. Refer to Engine Control Module Replacement .

Did you complete the replacement?

--

Go to Step 20

--

20

  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.

Did the DTC fail this ignition?

--

Go to Step 2

Go to Step 21

21

Are there any DTCs that have not been diagnosed?

--

Go to Diagnostic Trouble Code (DTC) List

System OK