Circuit Description

VCM tests exhaust gas recirculation valve by momentarily commanding valve on while monitoring manifold absolute pressure. If expected manifold absolute pressure increase is not seen under certain operating conditions (decel) for a calibrated number of tests, VCM will turn on Malfunction Indicator Light (MIL) and store DTC P0401.

VCM will run EGR tests when following conditions are present:

• No TP sensor DTCs are set.
• No MAP sensor DTCs are set.
• No VSS DTCs are set.
• No IAT sensor DTCs are set.
• No ECT sensor DTCs are set.
• No IAC DTCs are set.
• No linear EGR pintle position DTCs are set.
• No transmission DTCs are set.
• No HVAC DTCs are set.
• Engine coolant temperature is greater than 172°F (78°C).
• Baro is greater than 70 kPa (less than 10,3000 ft.).
• Vehicle speed is greater than 30 MPH.
• AC clutch status is unchanged.
• Transmission is in locked or unlocked stage (stable).
• No misfire DTCs are set.
• Engine speed is 1000-1600 RPM.

DTC will set when the following conditions are present:

• EGR flow test will fail and DTC P0401 set if VCM does not detect a sufficient rise in manifold absolute pressure during listed conditions.