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Home >> Buick >> 2007 >> Lucerne CX >> Repair and Diagnosis >> External Pages >> Different car >> Section 66 (Engine Control System - 3.8L (DTC P0140 To DTC 0412)) >> Diagnosis >> DTC P0411 (L26, Nu3) >> System Description

System Description

WARNING: This page is about a different car, the 2005 Buick LaCrosse and 2005 Buick Allure. However, it is still accessible from the selected car via links, so may be relevant.

The secondary air injection (AIR) system aids in the reduction of hydrocarbon emissions during a cold start. The system forces fresh filtered air into the exhaust stream in order to accelerate the catalyst operation. An electric air pump, the secondary AIR injection pump, provides filtered air on demand to the AIR control solenoid valve/pressure sensor assembly. The AIR control solenoid valve/pressure sensor assembly controls the flow of air from the AIR pump to the exhaust manifold. The AIR valve relay supplies the current needed to operate the AIR control solenoid valve/pressure sensor assembly. A pressure sensor is used to monitor the air flow from the AIR pump. The powertrain control module (PCM) supplies the internal pressure sensor with a 5-volt reference, an electrical ground, and a signal circuit.

The AIR diagnostic uses 3 phases to test the AIR system:

  1. DTCs P0411 and P2430 run during Phase 1
  2. DTCs P2430 and P2440 run during Phase 2
  3. DTC P2444 runs during Phase 3

In all 3 phases, testing is accomplished by comparing the measured pressure against the expected pressure. The PCM can detect faults in the AIR pump, AIR control solenoid valve/pressure sensor assembly, and the exhaust check valve. The pressure sensor can also detect leaks and restrictions in the secondary AIR system plumbing.

DTC P0411 Secondary Air Injection (AIR) System Insufficient Flow diagnostic monitors system airflow. This diagnostic test detects insufficient system flow due to a malfunctioning AIR control solenoid valve/pressure sensor assembly or AIR valve relay; a malfunctioning AIR pump or AIR pump relay; or a restricted or leaking system. When the PCM detects AIR system flow is not sufficient DTC P0411 sets. DTC P0411 runs during Phase 1.

Phase 1

The PCM commands the AIR pump ON and the AIR control/shut-off valve OPEN.

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