P0404-EGR POSITION SENSOR RATIONALITY OPEN

For a complete wiring diagram Refer to Section 8W.

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:
Engine running.
Set Condition:
The EGR flow or valve movement is not what is expected. A rationality error has been detected fro the EGR Close Position Performance. Two trip fault.

Possible Causes

EXCESSIVE RESISTANCE IN THE (F856) 5-VOLT SUPPLY CIRCUIT

(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. (Refer to 9 - ENGINE - DIAGNOSIS AND TESTING).

Diagnostic Test

1.ACTIVE DTC

NOTE: It may be necessary to drive the vehicle to meet the conditions to set this DTC, try to repeat the conditions in which the fault originally set by reviewing the Freeze Frame data.

Is the DTC Active or Pending at this time?

Yes

Go To 2

Refer to the INTERMITTENT CONDITION Diagnostic Procedure.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)

2.EGR POSITION VOLTAGE

NOTE: Diagnose all other EGR DTC(s) before continuing.

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

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.

Is the resistance below 5.0 ohms?

Yes

Go To 4

Repair the excessive resistance in the (F856) 5-volt Supply circuit.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)

4.(K34) EGR SENSOR SIGNAL CIRCUIT SHORTED TO GROUND

Is the resistance below 5.0 ohms?

Yes

Repair the short to ground in the (K34) EGR Sensor Signal circuit.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)

Replace the EGR Assembly.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)

5.(K35) EGR SOLENOID CONTROL CIRCUIT

Does EGR Solenoid operate while actuating and then turn off when actuation test is stopped?

a. Yes

Refer to the INTERMITTENT CONDITION Diagnostic Procedure.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)

Refer to the P0403-EGR Control Circuit diagnostic procedure and continue.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)

6.(K34) EGR SENSOR SIGNAL CIRCUIT

Is the voltage above 4.30 volts?

Yes

Go To 7

Go To 8

7.(K900) SENSOR GROUND CIRCUIT OPEN

Is the resistance below 5.0 ohms?

Yes

Replace the EGR Assembly.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)

Repair the open in the (K900) Sensor ground circuit.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)

8.(K34) EGR SENSOR SIGNAL CIRCUIT OPEN

Is the resistance below 5.0 ohms?

Yes

Go To 9

Repair the open in the (K34) EGR Sensor Signal circuit.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)

9.PCM

NOTE: Before continuing, check the PCM harness connector terminals for corrosion, damage, or terminal push out. Repair as necessary.

Were there any problems found?

Yes

Repair as necessary.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)

Replace and program the Powertrain Control Module per Service Information.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)