Secondary Air Injection, P2440 | Buick LaCrosse

🚗 2007 Buick LaCrosse

• The car came in with check engine light and a code
  • P2440 Secondary Air Injection System Switching Valve stuck open

🩺 Diagnosis

Secondary Air System on this vehicle includes:

• secondary air pump
• air valve assembly
• air pressure sensor (built in the air valve)

This system checks itself on start up, going through 3 different phases:

• During phase 1, both the AIR pump and the solenoid valve are activated.
  • Normal secondary air function occurs.
  • Expected system pressure is 8–10 kPa (1.16-1.45 PSI) above BARO.
• During phase 2, only the AIR pump is activated. The solenoid valve is closed.
  • Pressure sensor performance and solenoid valve deactivation are tested.
  • Expected system pressure is approximately 15–22 kPa (2.18-3.19 PSI) above BARO.
• During phase 3, neither the AIR pump nor the solenoid valve is activated.
  • AIR pump deactivation is tested.
  • Expected system pressure equals BARO.

On this vehicle I’ve noticed that the air pump is not pushing air into the engine but sucking it out from it. That defeats the whole purpose of the secondary air system which is to control emissions during the first 20 to 120 seconds of engine operation by forcing air downstream into the exhaust manifolds to oxidize the hydrocarbons and carbon monoxide created by running rich at start up.

After a little inspection I found red and black wires on the pump reversed. Customer told me they replaced the air pump with a Dorman aftermarket one previously.

So I swapped wires back in the correct terminal and fixed the problem, right? Wrong! Yes, air was now flowing in the right direction (into the engine), but it still failed self-test on Phase 2.

• With Pump On Valve Off pressure sensor displayed 5kPa above BARO (should be 8-10kPa)
• With Pump On Valve On (blocking the flow) – 10kPa above BARO (should be 15-22kPa)
• With Pump Off Valve Off – 0kPa.

After checking for leaks and testing pressure sensors, we concluded that the air pump is not strong enough to meet the specs.
After installing OEM air pump, during self-test pressure jumped up to within specs (10kPa, 20kPa, and 0kPa respectively)

Conclusion, whenever possible, buy OEM parts to avoid chasing your tail later.