Cruze

DTC P0401 or P0402

The engine control module (ECM) performs a insufficient flow test on the exhaust gas recirculation (EGR) system during deceleration and an excessive flow test during engine crank.

The insufficient flow test is when the ECM momentarily commanding the EGR valve to open while monitoring the signal of the manifold absolute pressure (MAP) sensor and the EGR position sensor. If the MAP signal is incorrect for the EGR pintle position, the ECM records the amount of MAP difference that was detected and adjusts a calibrated fail counter towards a calibrated fail threshold level. The number of EGR flow tests required to exceed the fail threshold may vary according to the amount of detected EGR flow error. The ECM will only allow one EGR flow test during an ignition cycle. Following a code clear event, the ECM will perform multiple EGR flow tests.

The excessive flow test is when the ECM monitors the position of the EGR valve during engine crank. The EGR valve should not be open during engine crank.

P0401 00

P0402 00

P0401 00

The MAP changes monitored by the ECM during the EGR flow tests indicate an insufficient amount of EGR flow.

P0402 00

The ECM detects excessive EGR flow due to the EGR valve pintle being open greater than 55% during crank.

The mounting bracket for the coil assembly provides the ground for the ignition coils. Ensure the mounting bolts are torqued to the correct specification. Refer to Fastener Tightening Specifications .

Schematic Reference

Engine Controls Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Exhaust Gas Recirculation (EGR) System Description

Electrical Information Reference

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References for scan tool information

1. Engine running, observe the DTC information with a scan tool. Verify that DTCs P0106 00, P0107 00, P0108 00, P0403 00, P0404 00, P0405 00 and P0406 00 are not set.

⇒	If any of the DTCs are set, refer to Diagnostic Trouble Code (DTC) List - Vehicle

2. Observe the DTC information with a scan tool. DTCs P0401 00 or P0402 00 should not set.
3. Ignition ON, observe the scan tool EGR Position Sensor parameter. The reading should be between 0-4%.
4. 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.

1. Verify none of the following conditions exist:

•	Incorrect EGR valve for engine application

•	A vacuum leak between the EGR valve and the intake manifold

•	Signs of external leakage usually indicated by carbon build-up around the mating surfaces of the components or an audible exhaust noise

•	Restrictions in the passages or EGR valve caused by carbon deposits or casting flash

•	Leaks or restrictions at the MAP sensor

Note: Restrictions can cause excessive back pressure and low engine vacuum.

•	Leaking, restricted, or revised exhaust system - refer to Symptoms - Engine Exhaust

•	Mechanical failure in the engine such as worn piston rings, camshaft or incorrect timing belt installation - refer to Symptoms - Engine Mechanical

2. Ignition OFF, disconnect the harness connector at the Q14 Exhaust Gas Recirculation Valve.
3. Ignition OFF, verify a test lamp does not illuminate between the control circuit terminal C and B+.

⇒	If test lamp illuminates, test the control circuit for a short to ground. If the circuit tests normal, replace the K20 Engine Control Module.

4. If all circuits test normal, test or replace the Q14 Exhaust Gas Recirculation Valve.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.