P0404
P0404-EGR POSITION SENSOR PERFORMANCE
For a complete wiring diagram Consult Diagrams/Electrical.
Theory of Operation
The EGR valve has a position sensor and the EGR position rationality is designed to make sure that the valve moves freely within its operating range. Closed valve position reference check verifies that the valve is within its allowable upper and lower limits. The EGR position rationality test looks for a sustained error relative to commanded valve position.
- 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 below 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.Initial Inspection and Diagnostic Overview
Diagnostic Test
1. DTC IS ACTIVE
NOTE: 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.
WARNING: 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.
WARNING: 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.
NOTE: Attempt to operate the vehicle under conditions similar to which the DTC was set.
NOTE: 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 DTC Active or Pending at this time?
Yes
- Go to 2
No
- Refer to the *CHECKING FOR AN INTERMITTENT DTC Diagnostic Procedure. Checking For An Intermittent DTC
2. (F856) 5 VOLT SUPPLY CIRCUIT HIGH RESISTANCE
Turn the ignition off.
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 (F856) 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.
WARNING: 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 below 0.5 volts?
Yes
- Go to 3
No
- Repair the (F856) 5 Volt Supply circuit for high resistance.
- Perform the PCM Verification Test. Powertrain Verification Test
3. (K34) EGR SIGNAL CIRCUIT HIGH RESISTANCE
Turn the ignition off.
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 (K34) 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.
WARNING: 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 below 0.5 volts?
Yes
- Go to 4
No
- Repair the (K34) EGR Signal circuit for high resistance.
- Perform the PCM Verification Test. Powertrain Verification Test
4. (K900) SENSOR GROUND CIRCUIT HIGH RESISTANCE
Turn the ignition off.
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 (K900) 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.
WARNING: 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 below 0.5 volts?
Yes
- Go to 5
No
- Repair the (K900) Sensor Ground circuit for high resistance.
- Perform the PCM Verification Test. Powertrain Verification Test
5. (Z902) GROUND CIRCUIT OPEN OR HIGH RESISTANCE
Turn the ignition off.
Disconnect the EGR Valve Assembly harness connector.
Using a 12 volt test light connected to the 12 volts, check the (Z902) Ground circuit in the EGR Valve Assembly harness connector.
NOTE: The test light should be illuminated and bright. Compare the brightness to that of a direct connection to the battery.
Is the test light illuminated and bright?
Yes
- Go to 6
No
- Repair the (Z902) Ground circuit for an open circuit of high resistance.
- Perform the PCM Verification Test. Powertrain Verification Test
6. (K35) 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 (K35) 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.
WARNING: 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 below 0.5 volts when the valve was opened during the system test?
Yes
- Go to 7
No
- Repair the (K35) EGR Control circuit for excessive resistance.
- Perform the PCM Verification Test. Powertrain Verification Test
7. EGR VALVE ASSEMBLY
Using the wiring diagram/schematic as a guide, inspect the wiring and connectors between the EGR Valve Assembly and the Powertrain Control Module (PCM).
Look for any chafed, pierced, pinched, or partially broken wires.
Look for broken, bent, pushed out or corroded terminals.
Verify that there is good pin to terminal contact in the Solenoid and the Powertrain Control Module connectors.
Search for 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. Powertrain Verification Test
No
- Replace the EGR Valve Assembly.
- Perform the PCM Verification Test. Powertrain Verification Test