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P0416 OBD-II Trouble Code: Secondary Air Injection System Switching Valve B Circuit Open

diagnostic check engine light

P0416 code definition

The powertrain control module (PCM) has detected a problem in the secondary air injection system, which reduces emissions by pumping ambient air into the exhaust stream.

What the P0416 code means

The PCM reads the condition of the secondary air injection system in increments of pressure and flow, which translate to input voltage from sensors. If input readings fluctuate by more than ten percent, a code will be stored and the malfunction indicator lamp (MIL) will illuminate. Some models require multiple drive cycles for the MIL to illuminate, but the code will usually be stored on the initial incident.

What causes the P0416 code?

  • Icing inside the pump in cold weather, due to a failed check valve which allows water or condensation to enter the pump and freeze

What are the symptoms of the P0416 code?

How does a mechanic diagnose the P0416 code?

Usually driven by the serpentine belt, the secondary air injection system uses a pump often called the “smog pump” to inject ambient air into the exhaust stream, reducing emissions. Heat-resistant silicon hoses direct cooler ambient air to the pump, while filtered air comes in through the air filter housing. This cooler air is directed into the exhaust system with silicon and steel lines, with a one-way check valve fitted on each exhaust hose to prevent condensation from backing up into the pump and causing problems. These valves are prone to failure.

Engines that use a V configuration usually feature dual inlet ports in the exhaust pipes and dual one-way check valves from the pump.

  • Test the check valves by attempting to blow air through them from both directions. Air should only flow through the valve in a single direction.
  • If air can flow through the valve in both directions, the valve has failed and should be replaced.
  • Inspect the hoses, lines and fittings for cracking, looseness and deterioration. Replace as needed.
  • If the check valves and lines all appear to be in good shape, perform a visual inspection of wiring, connectors and components. Repair/replace any damaged, disconnected, shorted or corroded parts as needed.
  • Connect a scanner or code reader to the diagnostic connector and record any stored codes.
  • Clear codes and test drive to see if codes return.
  • Check system fuses, referring to service manual for fuse location and values. Replace any blown fuses as needed.
  • After fuses are replaced, operate the secondary air injection system.
  • If fuse continues to blow, inspect for electrical shorts.

Common mistakes when diagnosing the P0416 code

Replacing the secondary air injection pump without devising a water drain on the pump housing can lead to repeated failures of the pump. It’s also essential to test one-way check valves for a proper diagnosis.

How serious is the P0416 code?

A P0416 code can lead to an illuminated MIL and a failed emissions test.

What repairs can fix the P0416 code?

  • Replacement of secondary air injection system pump
  • Replacement of secondary air injection system pump check valves
  • Repair/replacement of lines going to and from secondary air injection system pump

Additional comments for consideration regarding the P0416 code

More often than not, the check valves or the secondary air injection system pump are at fault. Failed check valves can introduce water back into the pump, and in cold weather this can cause the pump to seize or cause other types of catastrophic failure. Diagnosis should start with inspection of the pump and check valves. Other emissions-related codes may accompany a P0416 code, but it’s important to start with these components first.

Need help with a P0416 code?

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The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details
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