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For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2004 🢒 TopKick C-Series (Conventional) C4/C5 🢒 Engine 🢒 Engine Controls - 6.6L (LLY) 🢒 DTC P0404

Circuit Description

The engine control module (ECM) uses the exhaust gas recirculation (EGR) position sensor to determine the position of the EGR valve. The ECM sends a reference voltage through the 5-volt reference circuit to the EGR position sensor. The ECM provides a voltage return path for the sensor through the low reference circuit. A variable voltage signal, based on the EGR valve position, is sent from the sensor to the ECM through the EGR position sensor signal circuit. The ECM compares the actual EGR position with the desired EGR position when the EGR valve is commanded open or closed. If the ECM detects a variance between the actual EGR position and desired EGR position for a calibrated amount of time while the EGR valve is commanded open, 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 P0642, P0643 are not set.
    • The engine is running for more than 0.5 seconds.
    • The ignition voltage is between 11-18 volts.
    • The intake air temperature (IAT) is between 0-150.75°C (32-303.35°F)
    • The engine coolant temperature (ECT) is between 57-99.75°C (134.6-211.6°F)
    • The barometric pressure (BARO) is more than 72 kPa.
    • The power take off (PTO) is not engaged.
    • The desired EGR valve position is more than 3 percent.
    • This diagnostic runs continuously while the above conditions are met.

Conditions for Setting the DTC
    • The difference between the actual EGR position and the desired EGR position is more than 6 percent.
    • The above condition is present for more than 5 seconds

Action Taken When the DTC Sets
    • The control module stores the DTC information into memory when the diagnostic runs and fails.
    • The malfunction indicator lamp (MIL) will not illuminate.
    • The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Failure Records.
    • The driver information center, if equipped, may display a message.

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.

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

    Important: 

       • Attaching the shop exhaust system to the vehicle may cause false exhaust gas recirculation (EGR) DTCs to set.
       • Performing the EGR Solenoid output control function may result in setting EGR system DTCs.

  1. Start the engine.
  2. Observe the EGR Position Variance parameter while commanding the exhaust gas recirculation (EGR) valve from 0-30 percent with a scan tool.
  3. Exit the EGR output control function.

Did the EGR Position Variance parameter read more than the specified value when commanded with a scan tool?

6%

Go to Step 4

Go to Step 3

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 cycle?

--

Go to Step 4

Go to Intermittent Conditions

4

Is DTC P0403, P0405, or P0406 also set?

--

Go to DTC P0403 or DTC P0405 or DTC P0406

Go to Step 5

5

Test for shorted terminals and poor connections at the exhaust gas recirculation (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 16

Go to Step 6

6

Important: Failure to follow the below procedure can result in inaccurate test results.

Important: Direct battery voltage to the EGR valve motor is not to exceed 5 seconds.

  1. Disconnect the EGR valve.
  2. Start the engine.
  3. Measure the ignition voltage at the battery and note as supply voltage.
  4. Connect a 5-amp fused jumper between the battery positive terminal and the high control circuit terminal on the EGR valve.
  5. Set up the DMM to measure amperage. Refer to Circuit Testing in Wiring Systems.
  6. Connect a DMM between the battery negative terminal and the low control circuit terminal on the EGR valve.
  7. Measure the amperage and note as current draw.
  8. Remove the DMM and the 5-amp fused jumper wire.
  9. Divide the supply voltage by the current draw in order to calculate the resistance of the EGR valve motor coil.

Is the calculated resistance within the specified value for the specified EGR coil case temperature?

-40°C (-40°F) 1.42-2.88ohms

25°C (77°F) 1.62-3.28ohms

90°C (194°F) 1.75-3.66ohms

150°C (302°F) 1.89-4.05ohms

Go to Step 7

Go to Step 14

7
  1. Measure the voltage from the 5-volt reference circuit of the EGR position sensor to a good ground with a DMM and note as "supply voltage".
  2. Connect a test lamp and a DMM in series between the 5-volt reference circuit of the EGR position sensor and the low reference circuit of the EGR position sensor.
  3. Measure the amperage and note as "current draw".
  4. Remove the DMM and connect the test lamp between the 5-volt reference circuit of the EGR position sensor and the low reference circuit of the EGR position sensor.
  5. Connect a DMM in parallel between the 5-volt reference circuit of the EGR position sensor and a good ground.
  6. Measure the voltage and note as "load voltage drop".
  7. Subtract the "load voltage drop" from the "supply voltage" and divide your answer by the "current draw" in order to calculate the resistance in the 5-volt reference circuit.

Is the calculated resistance more than the specified value?

300 ohms

Go to Step 10

Go to Step 8

8
  1. With the test lamp still connected, connect a DMM in parallel between the low reference circuit of the EGR position sensor and a good ground.
  2. Measure and note the "low reference voltage drop".
  3. Divide the "low reference voltage drop" by the "current draw" measured in the previous step in order to calculate the resistance in the low reference circuit.

Is the calculated resistance more than the specified value?

5 ohms

Go to Step 10

Go to Step 9

9
  1. Remove the test lamp and the DMM.
  2. Connect a jumper wire between the 5-volt reference circuit of the EGR position sensor and the signal circuit of the EGR position sensor.
  3. Observe the EGR Sensor parameter with a scan tool.

Is the voltage more than the specified value?

4.9 V

Go to Step 11

Go to Step 10

10

Test for shorted terminals and poor connections at the engine control module (ECM). 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 16

Go to Step 12

11
  1. Turn OFF the ignition.
  2. Disconnect the ECM.
  3. Test the EGR motor high and low control circuits for high resistance. Refer to Circuit Testing in Wiring Systems.

Is the resistance more than the specified value?

High Control Circuit = -7 ohms

Low Control Circuit = -9 ohms

Go to Step 12

Go to Step 13

12

Repair the high resistance in the affected circuit. Refer to Circuit Testing and to Wiring Repairs in Wiring Repairs.

Did you find and correct the condition?

--

Go to Step 16

Go to Step 15

13
  1. Remove the EGR valve. Refer to Exhaust Gas Recirculation Valve Replacement
  2. Inspect for debris that will cause the EGR valve to stick.

Did you find and correct the condition?

--

Go to Step 16

Go to Step 14

14

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

Did you complete the replacement?

--

Go to Step 16

--

15

Replace the ECM. Refer to Engine Control Module Replacement .

Did you complete the replacement?

--

Go to Step 16

--

16
  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 17

17

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