P0404
SYMPTOM
P0404-EGR POSITION SENSOR PERFORMANCE
WHEN MONITORED
Engine running.
SET CONDITION
The EGR flow or valve movement is not what is expected.
POSSIBLE CAUSES
- EXCESSIVE RESISTANCE IN (F856) 5-VOLT SUPPLY
- (K35) EGR SOLENOID CONTROL CIRCUIT
- (K34) EGR SENSOR SIGNAL CIRCUIT OPEN
- (K34) EGR SENSOR SIGNAL CIRCUIT SHORTED TO GROUND
- (K900) SENSOR GROUND CIRCUIT OPEN
- EGR SOLENOID ASSEMBLY
- PCM
Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. Scan Tool Testing and Procedures
DIAGNOSTIC TEST
1. ACTIVE DTC
Ignition on, engine not running. With a scan tool, read DTCs.
Is the DTC active at this time?
Yes>> Go To 2
No>> Perform (NGC) POWERTRAIN VERIFICATION TEST VER-5. Powertrain Verification Test - Ver 5
2. EGR POSITION VOLTAGE
Note: Diagnose all other EGR DTC(s) before continuing.
Start the engine.
With a scan tool, read the EGR Position Sensor voltage.
Choose a conclusion that best matches the EGR voltage reading.
Below 3.5 volts
Go To 3
Between 3.5 volts to 4.3 volts
Go To 5
Above 4.3 volts
Go To 6
3. EXCESSIVE RESISTANCE IN THE (F856) 5-VOLT SUPPLY CIRCUIT
Turn the ignition off. Disconnect the EGR Solenoid harness connector.
Disconnect the PCM harness connectors.
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 to perform diagnosis.
Measure the resistance of the (F856) 5-volt Supply circuit from the EGR Solenoid harness connector to the appropriate terminal of special tool # 8815.
Is the resistance below 5.0 ohms?
Yes>> Go To 4
No>> Repair the excessive resistance in the (F856) 5-volt Sup ply circuit. Perform (NGC) POWERTRAIN VERIFICATION TEST VER-5.
4. (K34) EGR SENSOR SIGNAL CIRCUIT SHORTED TO GROUND
Measure the resistance between ground and the (K34) EGR Sensor Signal circuit in the EGR Solenoid harness connector.
Is the resistance below 5.0 ohms?
Yes>> Repair the short to ground in the (K34) EGR Sensor Signal circuit. Perform (NGC) POWERTRAIN VERIFICATION TEST VER-5.
No>> Replace the EGR Assembly. Perform (NGC) POWERTRAIN VERIFICATION TEST VER-5.
5. (K35) EGR SOLENOID CONTROL CIRCUIT
Ignition on, engine not running.
With the scan tool, actuate the EGR Solenoid.
Allow the EGR Solenoid to actuate for at least 15 seconds.
Feel the EGR Solenoid for operation. Stop actuation.
Does EGR Solenoid operate while actuating and then turn off when actuation test is stopped? Yes>> Perform (NGC) POWERTRAIN VERIFICATION TEST VER-5.
No>> Perform (NGC) POWERTRAIN VERIFICATION TEST VER-5.
6. (K34) EGR SENSOR SIGNAL CIRCUIT
Turn the ignition off.
Disconnect the EGR Solenoid harness connector.
Ignition on, engine not running.
Measure the voltage of the (K34) EGR Sensor Signal circuit in the EGR Solenoid harness connector.
Is the voltage above 4.30 volts?
Yes>> Go To 7
No>> Go To 8
7. (K900) SENSOR GROUND CIRCUIT OPEN
Turn the ignition off.
Disconnect the PCM harness connectors.
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 to perform diagnosis.
Measure the resistance of the (K900) Sensor ground circuit from the EGR Solenoid harness connector to the appropriate terminal of special tool # 8815.
Is the resistance below 5.0 ohms?
Yes>> Replace the EGR Assembly. Perform (NGC) POWERTRAIN VERIFICATION TEST VER-5.
No>> Repair the open in the (K900) Sensor ground circuit. Perform (NGC) POWERTRAIN VERIFICATION TEST VER-5.
8. (K34) EGR SENSOR SIGNAL CIRCUIT OPEN
Turn the ignition off.
Disconnect the PCM harness connectors.
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 to perform diagnosis.
Measure the resistance of the (K34) EGR Sensor Signal circuit from the EGR Solenoid harness connector to the appropriate terminal of special tool # 8815.
Is the resistance below 5.0 ohms?
Yes>> Go To 9
No>> Repair the open in the (K34) EGR Sensor Signal circuit. Perform (NGC) POWERTRAIN VERIFICATION TEST VER-5.
9. (K34) EGR SENSOR SIGNAL CIRCUIT SHORTED TO GROUND
Measure the resistance between ground and the (K34) EGR Sensor Signal circuit in the EGR Solenoid harness connector.
Is the resistance below 100 ohms?
Yes>> Repair the short to ground in the (K34) EGR Sensor Signal circuit. Perform (NGC) POWERTRAIN VERIFICATION TEST VER-5.
No>> Go To 10
10. PCM
Note: Before continuing, check the PCM harness connector terminals for corrosion, damage, or terminal push out. Repair as necessary.
Using the schematics as a guide, inspect the wire harness and connectors. Pay particular attention to all Power and Ground circuits.
Were there any problems found?
Yes>> Repair as necessary. Perform (NGC) POWERTRAIN VERIFICATION TEST VER-5.
No>> Replace and program the Powertrain Control Module per Service Information. Perform (NGC) POWERTRAIN VERIFICATION TEST VER-5.