Circuit Description
An exhaust gas recirculation (EGR) system is used to lower nitrogen oxide (NOx) emission levels caused by high combustion temperatures. It accomplishes this by feeding small amounts of exhaust gases back into the combustion chamber. When the air/fuel mixture is diluted with the exhaust gases, combustion temperatures are reduced.
A linear EGR valve is used on this system. The linear EGR valve is designed to accurately supply exhaust gases to the engine without the use of intake manifold vacuum. The valve controls exhaust flow going into the intake manifold from the exhaust manifold through an orifice with an engine control module (ECM) controlled pintle. The ECM controls the pintle position using inputs from the throttle position (TP) and manifold absolute pressure (MAP) sensors. The ECM then commands the EGR valve to operate when necessary by controlling an ignition signal through the ECM. This can be monitored on a scan tool as the Desired EGR Position.
The ECM monitors the results of its command through a feedback signal. By sending a 5-volt reference and a ground to the EGR valve, a voltage signal representing the EGR valve pintle position is sent to the ECM. This feedback signal can also be monitored on a scan tool and is the actual position of the EGR pintle. The Actual EGR Position should always be near the commanded or Desired EGR Position.
This diagnostic trouble code (DTC) will detect an open valve position.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC P0404 Exhaust Gas Recirculation (EGR) Open Position Performance
Conditions for Running the DTC
| • | DTCs P0112, P0113, P0405, P0406, and P0502 are not set. |
| • | The ignition voltage is between 11-15.8 volts. |
| • | The intake air temperature is between 3-120°C (37.4-248°F). |
| • | Start up engine coolant temperature (ECT) is more than 10°C (50°F). |
| • | Engine coolant temperature is more than 65°C (149°F). |
| • | The desired EGR position is more than 0 percent and steady within 3 percent. |
| • | Air fuel ratio is more than 14.5-1. |
| • | DTC P0404 runs continuously every 125 milliseconds when the above conditions are met. |
Conditions for Setting the DTC
| • | The difference between current and commended position is greater than 15 percent. |
| • | The Desired EGR Position is greater than 0. |
| • | Change in desired EGR is less than 3 percent. |
| • | The engine is running. |
| • | The intake air temperature (IAT) is between 3-120°C (37.4-248°F). |
| • | Ignition voltage is between 11-15.8 volts. |
| • | Start up coolant temperature is greater than 10°C (50°F). |
| • | Coolant temperature is greater than 65°C (149°F). |
| • | Air fuel ratio is greater than 14.5-1. |
| • | DTCs P0112, P0113, P0405, P0406, and P0502 are not set. |
Action Taken When the DTC Sets
| • | The control module illuminates the malfunction indicator lamp (MIL) on the third 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 4 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
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 problem 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 Controls Connector End Views | ||||||||||
1 | Did you perform the Diagnostic System Check - Engine Controls? | -- | Go to Step 2 | |||||||
2 | Is DTC P0405 or P0406 also set? | -- | Go to Step 3 | |||||||
3 |
Is the percentage less than the specified value? | 15% | Go to Step 4 | Go to Step 5 | ||||||
4 |
Did the DTC fail this ignition? | -- | Go to Step 5 | Go to Intermittent Conditions | ||||||
5 |
Observe the EGR Position Sensor parameter with a scan tool. Is the parameter less than the specified value? | 1% | Go to Step 6 | Go to Step 13 | ||||||
6 |
Important: Use the J 35616-200 Test Lamp Kit for this test. If the J 35616-200 is not available, use a test lamp that measures between 25-30 ohms. 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 15 | Go to Step 14 | ||||||
8 |
Is the parameter more than the specified value? | 99% | Go to Step 9 | Go to Step 16 | ||||||
9 | Connect a test lamp between the ignition 1 voltage circuit of the EGR valve and a good ground. Does the test lamp illuminate? | -- | Go to Step 10 | Go to Step 20 | ||||||
10 |
Does the test lamp illuminate? | -- | Go to Step 11 | Go to Step 17 | ||||||
11 |
Is the resistance less than the specified value? | 3 ohms | Go to Step 12 | Go to Step 20 | ||||||
12 |
Is the voltage less than the specified value? | 0.5 V | Go to Step 18 | Go to Step 17 | ||||||
13 | Test the signal circuit of the EGR valve position sensor 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 23 | Go to Step 19 | ||||||
14 | 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 23 | Go to Step 19 | ||||||
15 | 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 23 | Go to Step 19 | ||||||
16 | Test the signal circuit of the EGR valve position sensor for the following conditions:
Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 23 | Go to Step 19 | ||||||
17 | 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 23 | Go to Step 19 | ||||||
18 | Test the EGR valve for the following:
Did you find and correct the condition? | -- | Go to Step 23 | Go to Step 21 | ||||||
19 | 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 23 | Go to Step 22 | ||||||
20 | Repair the ignition 1 voltage circuit of the EGR valve for one of the following conditions:
Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | Go to Step 23 | -- | ||||||
21 | Replace the EGR valve. Refer to Exhaust Gas Recirculation Valve Replacement . Did you complete the replacement? | -- | Go to Step 23 | -- | ||||||
22 | Replace the ECM. Refer to Engine Control Module Replacement . Did you complete the replacement? | -- | Go to Step 23 | -- | ||||||
23 |
Did the DTC fail this ignition? | -- | Go to Step 2 | Go to Step 24 | ||||||
24 | Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed? | -- | System OK | |||||||
