Circuit Description
An Exhaust Gas Recirculation (EGR) system is used to lower Oxides of Nitrogen (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 a PCM controlled pintle. The PCM controls the pintle position using inputs from the Throttle Position (TP) and Manifold Absolute Pressure (MAP) sensors. The PCM then commands the EGR valve to operate when necessary by controlling an ignition signal through the PCM. This can be monitored on a scan tool as the Desired EGR Position.
The PCM 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 PCM. 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. The PCM monitors the EGR valve pintle position input to ensure that the valve responds properly to commands from the PCM and to detect a fault if the pintle position sensor circuit is closed. If the PCM detects an closed pintle this DTC will set.
Conditions for Running the DTC
| • | DTCs P0107, P0108, P0112, P0113, P0117, P0118, not set. |
| • | Ignition voltage is greater than 11.7 V. |
| • | EGR commanded OFF (Desired EGR Position is 0 percent). |
Conditions for Setting the DTC
Actual EGR Position is greater than 20 percent for 10 seconds.
Action Taken When the DTC Sets
| • | The PCM turns on the malfunction indicator lamp (MIL) after 2 consecutive driving cycles with the fault active. |
| • | The PCM will record operating conditions at the time the diagnostic fails. The Freeze Frame and Failure Records buffers will store this information. |
| • | A history DTC is stored. |
| • | The EGR Valve is disabled. |
Conditions for Clearing the MIL/DTC
| • | The PCM turns the MIL OFF after 3 consecutive drive trips without a fault condition present. |
| • | A history DTC will clear if no fault conditions have been detected for 40 warm-up cycles (coolant temperature has risen 22°C (40°F) from the startup coolant temperature and the engine coolant temperature exceeds 70°C (160°F) during the same ignition cycle. |
| • | Use the scan tool Clear Information function. |
| • | Disconnect the PCM battery feed for 30 seconds. |
Diagnostic Aids
Due to the moisture associated with exhaust systems, the EGR valve may freeze and stick in colder 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 verified easily. Check the freeze frame data to determine if the DTC set when the vehicle was cold by viewing the Engine Coolant Temperature (ECT).
Test Description
Numbers below refer to the step numbers on the Diagnostic Table.
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The Powertrain OBD System Check prompts the technician to complete some basic checks and store the freeze frame and failure records data on the scan tool if applicable. This creates an electronic copy of the data taken when the malfunction occurred. The information is then stored on the scan tool for later reference.
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Commanding the EGR valve open determines whether the EGR system can control the EGR valve accurately and if the malfunction is present.
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When the EGR valve electrical connector is disconnected, the scan tool should display the Actual EGR Position as 0 percent. If it does not, the malfunction lies either in the EGR signal circuit or the PCM.
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If the EGR valve 5.0 volt reference is shorted to voltage, the DMM will read battery voltage and additional DTCs may be set and engine performance will be poor.
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The replacement PCM must be reprogrammed. Refer to the latest Techline procedures for PCM reprogramming.
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A poor electrical connection may have caused this DTC to set. The test light will still illuminate if the circuit is OK but the terminal connection was poor. Be sure to check the terminals for being backed out, improperly formed or damaged, and for poor tension.
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All circuits to the EGR valve are OK at this point. The malfunction lies internally in the EGR valve and therefore must be replaced. Be sure all gasket material is removed from the EGR mounting surface. Even a small amount of material may cause a DTC P0404 to set. Refer to the Exhaust Gas Recirculation Valve Replacement for the On Vehicle Service of the EGR valve.
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Check the terminals for being backed out, improperly formed or damaged, and for poor tension.
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Clearing the DTCs is a very important step for this diagnostic. The clearing function allows the EGR valve to relearn a new pintle position as the old position was inaccurate due to the malfunction that caused the DTC. The DTC must be cleared with the ignition switch ON, with the engine OFF or when the engine is idling. If the PCM sees a EGR command, the new pintle position will not be learned.
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If no malfunctions have been found at this point and no additional DTCs were set, refer to the Diagnostic Aids for additional checks and information.
Step | Action | Values | Yes | No |
|---|---|---|---|---|
Was the Powertrain On-Board Diagnostic (OBD) System Check performed? | -- | Go to | ||
Does the Actual EGR Position follow the Desired EGR Position? | 0%, 20%, 50%, 70%, 100% | |||
Disconnect the EGR valve electrical connector. Is the Actual EGR Position near the specified value? | 100% | |||
4 | Check the EGR valve signal circuit for a short to voltage and repair as necessary. Was a repair necessary? | -- | ||
Connect a DMM to ground and probe the EGR valve 5.0 V reference circuit terminal at the EGR valve electrical connector. Does the DVM read near the specified value? | 5.0 V | |||
Replace the PCM. Refer to Powertrain Control Module Replacement . Is the action complete? | -- | -- | ||
7 |
Does the test light illuminate? | -- | ||
8 | Check the EGR valve 5.0 V reference circuit for a short to voltage and repair as necessary. Was a repair necessary? | -- | ||
9 | Check the EGR valve ignition feed circuit for a short to voltage and repair as necessary. Was a repair necessary? | -- | ||
10 | Connect a test light to B+ and probe the EGR valve sensor ground circuit terminal. Does the test light illuminate? | -- | ||
Check the EGR valve sensor ground circuit terminal for a poor connection at the EGR valve electrical connector and repair as necessary. Refer to Wiring Repairs in Wiring Systems for the proper procedure. Was a repair necessary? | -- | |||
12 | Check the EGR valve sensor ground circuit for an open and repair as necessary. Was a repair necessary? | -- | ||
Replace the EGR valve. Refer to Exhaust Gas Recirculation Valve Replacement . Is the action complete? | -- | -- | ||
Check the PCM electrical connector for a poor connection and repair as necessary. Was a repair necessary? | -- | |||
Does the scan tool indicate that this diagnostic ran and passed? | -- | |||
Check if any additional DTCs are set. Are any DTCs displayed that have not been diagnosed? | -- | Go to the applicable DTC table | System OK. Go to Diagnostic Aids |
