Circuit Description
An exhaust gas recirculation (EGR) system is used in order to lower oxides of nitrogen (NOx) emission levels caused by high combustion temperatures. The EGR 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 in order 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 control module controlled pintle valve. The control module commands the EGR by applying a 12 volt duty cycle to the EGR valve. This can be monitored on a scan tool as desired EGR position.
The control module can monitor the pintle position with the EGR pintle position signal. This sensor uses a variable resistor with a 5 volt reference, a signal circuit, and a ground. The signal circuit monitors changes in voltage on the variable resistor as the pintle moves.
Conditions for Running the DTC
| • | The ECT is between 80°C-120°C(176°F-248°F). |
| • | The IAT is less than 100°C(212°F). |
| • | The desired EGR position is greater than 14 %. |
Conditions for Setting the DTC
The EGR pintle position voltage is 0.29 volt or greater, for more than 10 seconds, with the EGR valve commanded closed.
Action Taken When the DTC Sets
| • | The Malfunction Indicator Lamp (MIL) will illuminate. |
| • | The VCM will record operating conditions at the time the diagnostic fails. The Freeze Frame and Failure Records will store this information. |
| • | A history DTC is stored |
| • | The EGR Valve is disabled. |
Conditions for Clearing the MIL or DTC
| • | The control module turns OFF the MIL after 3 consecutive drive trips when the test has run and passed. |
| • | A history DTC will clear if no fault conditions have been detected for 40 warm-up cycles. A warm-up cycle occurs when the coolant temperature has risen 22°C (40°F) from the startup coolant temperature and the engine coolant reaches a temperature that is more than 70°C (158°F) during the same ignition cycle. |
| • | Use a scan tool in order to clear the DTCs. |
Diagnostic Aids
Excessive carbon deposits may cause a restriction of movement in the EGR pintle. This problem may be compounded in cold weather with moisture freezing in the valve. Check for full range operation in the EGR system with the scan tool.
Test Description
Number(s) below refer to the step number(s) on the Diagnostic Table.
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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%. If it does not, the malfunction lies either in the EGR signal circuit or the VCM.
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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.
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A poor electrical connection may have caused this DTC to set. Be sure to check the terminals for being backed out, improperly formed, damaged, and for poor tension.
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The replacement VCM must be programmed and the Crankshaft Position System Variation Learn Procedure must be performed. Refer to the latest Techline procedures for VCM programming.
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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 minimum pintle position as the old position was inaccurate due to the malfunction that caused the DTC. If the VCM sees an EGR command, the new minimum 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 | Value(s) | Yes | No |
|---|---|---|---|---|
1 |
Important: Before clearing the DTCs, use the scan tool in order to record the Freeze Frame and the Failure Records for reference. This information will be lost when the Clear DTC Information function is used. Was the Powertrain On-Board Diagnostic (OBD) System Check performed? | -- | ||
Does the Actual EGR Position follow the Commanded EGR Position? | 20%, 50%, 70%, 100% | |||
3 | This DTC is intermittent. Are any additional DTCs stored? | -- | Go to applicable DTC table | Go to Diagnostic Aids |
Disconnect the EGR valve electrical connector. Is the Actual EGR Position near the specified value? | 0% | |||
5 | Check the EGR valve signal circuit for a short to voltage and repair as necessary. Refer to Wiring Repairs in Repair Instructions. 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. Is the voltage near the specified value? | 5.0 V | |||
7 |
Is the test light ON? | -- | ||
8 | Check the EGR Valve 5.0 V reference circuit for a short to voltage and repair as necessary. Refer to Wiring Repairs in Repair Instructions. Was a repair necessary? | -- | ||
9 | Check the EGR Valve Feed Control circuit for a short to voltage and repair as necessary. Refer to Wiring Repairs in Repair Instructions. Was a repair necessary? | -- | ||
10 | Connect a test light to B+ and probe the EGR Valve Ground circuit terminal. Is the test light ON? | -- | ||
Check the EGR Valve Ground circuit terminal for a poor connection at the EGR Valve electrical connector and repair as necessary. Refer to Wiring Repairs in Repair Instructions. Was a repair necessary? | -- | |||
12 | Check the EGR Valve Ground circuit for an open and repair as necessary. Refer to Wiring Repairs in Repair Instructions. Was a repair necessary? | -- | ||
13 | Replace the EGR Valve. Refer to Exhaust Gas Recirculation Valve Replacement in Repair Instructions. Is the action complete? | -- | -- | |
14 | Check the VCM electrical connector for a poor connection and repair as necessary. Refer to Wiring Repairs in Repair Instructions. Was a repair necessary? | -- | ||
Is the action complete? | -- | -- | ||
Does the scan tool indicate that this diagnostic ran and passed? | -- | |||
Use the scan tool in order to display the Capture Info and the Review Capture Info functions. Are there any DTCs displayed that have not been diagnosed? | -- | Go to the applicable DTC table | System OK |
