P0401-EGR SOLENOID CIRCUIT NEGATIVE DEVIATION

For a complete wiring diagram Refer to Section 8W

When Monitored:
With the engine running.
Set Condition:
The ECM detects EGR flow is less than the requested flow.

Possible Causes

AIR FILTER

AIR RESTRICTION

CHECKING FOR AIR LEAKS

CHECKING THE EGR AIR FLOW CONTROL VALVE

CHECKING THE EGR COOLER AND TUBES

EGR VALVE

INTERMITTENT CONDITION

Diagnostic Test

1.CHECK FOR ACTIVE DTC

NOTE: If the ECM detects and stores a DTC, the ECM also stores the engine/vehicle operating conditions under which the DTC was set. Some of these conditions are displayed on the scan tool at the same time the DTC is displayed.

NOTE: Before erasing stored DTCs, record these conditions. Attempting to duplicate these conditions may assist when checking for an active DTC.

NOTE: If there are any Mass Air Flow DTC's, diagnose the MAF DTC's before continuing EGR diagnostics.

Did this DTC set again?

Yes

Go To 2

Refer to the *CHECKING FOR AN INTERMITTENT DTC Diagnostic Procedure. (Refer to 9 - ENGINE - DIAGNOSIS AND TESTING)

2.AIR FILTER

Were any of these problems found?

Yes

Replace the Air Filter element.
Perform the ECM Verification Test Ver. 1 (Refer to 9 - ENGINE - DIAGNOSIS AND TESTING).

Go To 3

3.AIR RESTRICTION

NOTE: Inspect all air intake, crankcase vent and turbocharger related tubes for damage, restriction or poor connection. Any of these conditions can cause this DTC to set.

NOTE: Inspect the exhaust system and related tubes for damage, restriction or poor connection. Any of these conditions can cause this DTC to set.

Were any problems found?

Yes

Repair or replace as necessary.
Perform the ECM Verification Test Ver. 1 (Refer to 9 - ENGINE - DIAGNOSIS AND TESTING).

Go To 4

4.CHECKING FOR AIR LEAKS

Is there evidence of smoke leakage?

Yes

Repair or replace as necessary.
Perform the ECM Verification Test Ver. 1 (Refer to 9 - ENGINE - DIAGNOSIS AND TESTING).

Go To 5

5.CHECKING EGR AIR FLOW CONTROL VALVE (EGR AFCV)

NOTE: The EGR AFCV should be normally open (allowing full air flow) then close during actuation.

Does the EGR AFCV close completely when actuated?

Yes

Go To 6

Replace the EGR Air Flow Control Valve.
Perform the ECM Verification Test Ver. 1 (Refer to 9 - ENGINE - DIAGNOSIS AND TESTING).

6.CHECKING EGR COOLER AND TUBES

NOTE: Compressed air ( at low pressure ) can be applied to the lower port of the EGR Cooler. When applying compressed air check for air to flow through cooler and out the upper port. Always wear safety glasses when working with compressed air.

Were any problems found?

Yes

Repair or replace as necessary.
Perform the ECM Verification Test Ver. 1 (Refer to 9 - ENGINE - DIAGNOSIS AND TESTING).

Replace the EGR Valve.
Perform the ECM Verification Test Ver. 1 (Refer to 9 - ENGINE - DIAGNOSIS AND TESTING).