DTC P0401 or P0402
Diagnostic Instructions
DTC Descriptors
| DTC P0401 00: Exhaust Gas Recirculation (EGR)
Flow Insufficient |
| DTC P0402 00: Exhaust Gas Recirculation (EGR)
Flow Excessive |
Circuit/System Description
The exhaust gas recirculation (EGR) valve is controlled by the
engine control module (ECM) through the EGR valve. A reference
voltage is supplied to the EGR valve. The ECM controls the valve by
grounding the control circuit.
Conditions for Running the DTC
| • |
The ignition is ON, or the
engine is running. |
| • |
The DTCs run continuously when
the above conditions are met. |
Conditions for Setting the DTC
P0401
The ECM detects the EGR flow is below a calibrated amount when the
EGR is commanded ON.
P0402
The ECM detects the EGR flow is above a calibrated amount when the
EGR is commanded OFF.
Action Taken When the DTC Sets
DTC P0401 and P0402 are Type B DTCs.
Conditions for Clearing the DTC
DTC P0401 and P0402 are Type B DTCs.
Reference Information
Schematic Reference
Engine Controls Schematics
Connector End View Reference
Component Connector End Views
Electrical Information Reference
DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions
Scan Tool Reference
Control Module References for scan tool information
Circuit/System Verification
| 1. |
Ignition ON, observe the DTC
information with a scan tool. Verify that no other DTCs are
set. |
| 2. |
DTCs P0401 or P0402 should not
set. |
| 3. |
Command the throttle plate
from 5–95% with a scan tool. The throttle plate should
respond to the scan tool commands. |
| 4. |
Command the EGR Valve from
5–95% with a scan tool. The EGR valve should respond to the
scan tool commands. |
| 5. |
Operate the vehicle within the
Conditions for Running the DTC to verify the DTC does not reset.
You may also operate the vehicle within the conditions that you
observed from the Freeze Frame/Failure Records data. |
Circuit/System Testing
| 1. |
Ignition OFF, inspect for the
following: |
| |
• |
Intake system/charge air hoses
for leaks/restrictions |
| |
• |
Exhaust system/turbo charger
for leaks/restrictions |
| |
• |
Air filter for
restrictions |
| 2. |
Engine running at idle,
command the EGR Valve to 95% with a scan tool. Verify that the mass
air flow (MAF) Sensor parameter is less than 5 g/s. |
| ⇒ |
If the parameter is greater than the specified
value, replace the Q14 Exhaust Gas Recirculation Valve. |
| 3. |
Command the EGR Valve to 5%
with a scan tool. Verify that the MAF Sensor parameter is greater
than 14 g/s. |
| ⇒ |
If the parameter is less than the specified value,
replace the Q14 Exhaust Gas Recirculation Valve. |
| 4. |
Verify the DTC does not
reset. |
| ⇒ |
If the DTC is set, replace the K20 Engine Control
Module. |
Repair Instructions
Perform the
Diagnostic Repair Verification after completing the diagnostic
procedure.
|
