P0404
P0404 - EGR Position Sensor Performance
For wiring diagrams, refer to.
• When Monitored: The PCM performs two diagnostic procedures to test the rationality of the EGR sensor signal: a position rationality test and a zero reference test. The position rationality test is performed continuously when the EGR control circuit is active. The zero reference test is performed when the valve is closed, with the throttle closed and engine RPM less than a calibrated threshold, when the PCM is attempting to learn the position of the EGR valve during the closed valve state.
• Set Condition: The PCM monitors the EGR position rationality by subtracting the actual position of the EGR valve from the desired position. If the value exceeds a calibrated value for a calibrated time, the test fails. If the PCM detects that the EGR position zero reference voltage is not within a valid range, the test fails. After two failed trips, a DTC is set and the MIL is illuminated.
• Always perform the pre-diagnostic troubleshooting procedure before proceeding. Refer to => Non-DTC Based Diagnostics. Pre-Diagnostic Troubleshooting Procedure
Test Step 1 - DTC is Active
• Diagnose and repair any EGR signal circuit high or low DTCs before continuing with this procedure.
• Turn the ignition ON.
• With the scan tool, select view DTCs. record DTC and freeze frame information.
• Start the engine and allow it to reach operating temperature.
When the engine is operating, do not stand in direct line with the fan. Do not put your hands near the pulleys, belts, or fan. Do not wear loose clothing. Failure to follow these instructions can result in personal injury or death.
The normal operating temperature of the EGR system is very high. Never work around or attempt to service any part of the EGR system until it has cooled.
• Attempt to operate the vehicle under conditions similar to which the DTC was set.
• It may be necessary to test drive the vehicle within the DTC monitoring conditions in order for this DTC to set.
• With a scan tool, select view DTCs.
Is the status active for this DTC?
Yes
• Go to Test Step 2 => [ Test
Step 2 - 5 Volt Supply Circuit High Resistance ]
No
• Refer to the checking for an intermittent DTC diagnostic procedure. Refer to => Non-DTC Based Diagnostics. Checking for an Intermittent DTC
Test Step 2 - 5 Volt Supply Circuit High Resistance
• Turn the ignition OFF.
Do not probe the PCM harness connectors. Probing the PCM harness connectors will damage the PCM terminals resulting in poor terminal to pin connection. Install Miller Special Tool #8815 along with the #8815-1 to perform the diagnosis.
• Using a voltmeter, perform a voltage drop test by backprobing the 5 volt supply circuit at the EGR valve assembly harness connector and probing the appropriate terminal of the special tool #8815. Make sure the voltmeter leads are connected so that positive polarity is displayed on the voltmeter.
When the engine is operating, do not stand in direct line with the fan. Do not put your hands near the pulleys, belts, or fan. Do not wear loose clothing. Failure to follow these instructions can result in personal injury or death.
• Start the engine.
Is the voltage less than 0.5 volts?
Yes
• Go to Test Step 3 => [ Test
Step 3 - EGR Signal Circuit High Resistance ]
No
• Repair the 5 volt supply circuit for high resistance.
• Perform the PCM Verification Test. Refer to => Non-DTC
Based Diagnostics. PCM Verification Test
Test Step 3 - EGR Signal Circuit High Resistance
• Turn the ignition OFF.
Do not probe the PCM harness connectors. Probing the PCM harness connectors will damage the PCM terminals resulting in poor terminal to pin connection. Install Miller Special Tool #8815 along with the #8815-1 to perform the diagnosis.
• Using a voltmeter, perform a voltage drop test by backprobing the EGR signal circuit at the EGR valve assembly harness connector and probing the appropriate terminal of the special tool #8815. Make sure the voltmeter leads are connected so that positive polarity is displayed on the voltmeter.
When the engine is operating, do not stand in direct line with the fan. Do not put your hands near the pulleys, belts, or fan. Do not wear loose clothing. Failure to follow these instructions can result in personal injury or death.
• Start the engine.
Is the voltage less than 0.5 volts?
Yes
• Go to Test Step 4 => [ Test
Step 4 - Sensor Ground Circuit High Resistance ]
No
• Repair the EGR signal circuit for high resistance.
• Perform the PCM Verification Test. Refer to => Non-DTC
Based Diagnostics. PCM Verification Test
Test Step 4 - Sensor Ground Circuit High Resistance
• Turn the ignition OFF.
Do not probe the PCM harness connectors. Probing the PCM harness connectors will damage the PCM terminals resulting in poor terminal to pin connection. Install Miller Special Tool #8815 along with the #8815-1 to perform the diagnosis.
• Using a voltmeter, perform a voltage drop test by backprobing the sensor ground circuit at the EGR valve assembly harness connector and probing the appropriate terminal of the special tool #8815. Make sure the voltmeter leads are connected so that positive polarity is displayed on the voltmeter.
When the engine is operating, do not stand in direct line with the fan. Do not put your hands near the pulleys, belts, or fan. Do not wear loose clothing. Failure to follow these instructions can result in personal injury or death.
• Start the engine.
Is the voltage less than 0.5 volts?
Yes
• Go to Test Step 5 => [ Test
Step 5 - Ground Circuit Open or High Resistance ]
No
• Repair the sensor ground circuit for high resistance.
• Perform the PCM Verification Test. Refer to => Non-DTC
Based Diagnostics. PCM Verification Test
Test Step 5 - Ground Circuit Open or High Resistance
• Turn the ignition OFF.
• Disconnect the EGR valve assembly harness connector.
• Using a test lamp connected to the 12 volts, check the ground circuit in the EGR valve assembly harness connector.
• The test lamp should be illuminated and bright. Compare the brightness to that of a direct connection to the battery.
Is the test lamp illuminated and bright?
Yes
• Go to Test Step 6 => [ Test
Step 6 - EGR Control Circuit High Resistance ]
No
• Repair the ground circuit for an open of high resistance.
• Perform the PCM Verification Test. Refer to => Non-DTC
Based Diagnostics. PCM Verification Test
Test Step 6 - EGR Control Circuit High Resistance
• Turn the ignition OFF.
• Connect the EGR Valve Assembly connector.
CAUTION: Do not probe the PCM harness connectors. Probing the PCM harness connectors will damage the PCM terminals resulting in poor terminal to pin connection. Install Miller Special Tool #8815 along with the #8815-1 to perform the diagnosis.
• Using a voltmeter, perform a voltage drop test by backprobing the EGR control circuit at the EGR valve assembly harness connector and probing the appropriate terminal of the special tool #8815. Make sure the voltmeter leads are connected so that positive polarity is displayed on the voltmeter.
• Start the engine and allow it to reach operating temperature.
When the engine is operating, do not stand in direct line with the fan. Do not put your hands near the pulleys, belts, or fan. Do not wear loose clothing. Failure to follow these instructions can result in personal injury or death.
• With the scan tool, perform the EGR system test.
• Select OPEN to open the EGR valve.
• Monitor the circuit voltage on the voltmeter.
Is the voltage less than 0.5 volts when the valve was opened during the system test?
Yes
• Go to Test Step 7 => [ Test
Step 7 - EGR Valve Assembly ]
No
• Repair the EGR control circuit for excessive resistance.
• Perform the PCM Verification Test. Refer to => Non-DTC
Based Diagnostics. PCM Verification Test
Test Step 7 - EGR Valve Assembly
• Using the wiring diagram/schematic as a guide, inspect the wiring and connectors between the EGR valve assembly and the PCM.
• Look for any chafed, pierced, pinched, or partially broken wires.
• Look for broken, bent, pushed out or corroded terminals.
• Refer to any technical service bulletins that may apply.
Were any problems found?
Yes
• Repair or replace the EGR system components as necessary.
• Perform the PCM Verification Test. Refer to => Non-DTC
Based Diagnostics. PCM Verification Test
No
• Replace the EGR valve assembly.
• Perform the PCM Verification Test. Refer to => Non-DTC
Based Diagnostics. PCM Verification Test