Circuit Description
INSERT GRAPHIC SMITL15AA
The linear exhaust gas recirculation (EGR) system consists of a linear EGR valve, the powertrain control module (PCM) and its associated wiring. The PCM directly controls the ground for the EGR valve when certain conditions have been met. Voltage is supplied by the UHJB to the EGR valve when the ignition is turned ON. When the PCM grounds the valve, a diagnostic feedback signal can determine if the valve had actually moved. Since the correct feedback voltage is possible, but the passage has restricted the flow, DTC P0401 was implemented.
Conditions for Setting the DTC
| • | If the commanded position is greater than 80 percent, the actual position must be within 26 counts , 10 percent, 5.0 volts of the commanded. |
| • | If the commanded position is less than 80 percent, the actual position must be within 60 counts, 24 percent, 1.1 volts of the commanded. |
DTC P0404 will be set if either condition exists for greater than 10 seconds.
When either one of these tests have failed, a DTC will set and the EGR will be disabled for that ignition cycle. The malfunction history record will indicate which one of these tests has failed to aid in diagnostics.
Important:
• The EGR position error is continuously checked when the EGR is commanded
ON. • The EGR valve ma operate at any engine coolant temperature regardless
of loop mode.
Diagnostic Aids
When attempting to diagnose an intermittent problem use the scan tool to review the malfunction history diagnostic information. The supplemental data can be used to duplicate a problem.
Check the tightness of the female terminal grip with a spare male terminal.
| • | B+ voltage is supplied to the E terminal on the EGR valve when the ignition is ON. |
| • | Check the EGR 10 amp fuse in the UHJB before diagnosing this DTC. |
| • | Carbon build-up around the pintle valve may restrict pintle movement. |
| • | An open in the diode feedback circuit will result in unstable valve operation resulting in vehicle surge. |
Test Description
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Normal closed valve position feedback voltage should be between 0.2.-1.5 volts. This value may change with temperature.
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A voltage of less than 0.2 volts indicates a problem with the position feedback circuit. A voltage of greater than 1.5 volts could be caused by a position feedback circuit problem, a valve stuck open or a solenoid being energized.
