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How to Fix a P0418 Code – Causes, Symptoms and Cost

  • Car Services
  • Xavier Sabastian
  • 5 minutes

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P0418 is a fault code that refers to a problem with the control circuit for the secondary air injection system. Continue reading to find out more.

Different systems make up modern vehicles, and they all work together to keep your ride functioning properly. For example, to lower emissions, the secondary air injection (SAI) system’s function is to pump new air into the exhaust stream. In addition, this technology aids the catalytic converter in many automobiles in reaching operational temperature as soon as the engine is started.

Code P0418

What does Code P0418 mean?

P0418 is the “Secondary Air Injection System Control “A” Circuit” Diagnostic trouble code (DTC). The A designation may refer to a particular circuit within the system or the whole circuit.

How the SAI System Works

Some cars include an SAI system that uses oxidation to minimize hazardous emissions. Either an electric pump or a belt-driven pump is included in this arrangement. This pump pulls ambient air, slightly compresses it, and then pumps the pressured air into the catalytic converter or exhaust manifolds. Your car’s powertrain control module (PCM) regulates and distributes air properly by controlling valves.

The PCM uses input voltage signals to track changes in air pressure. The PCM will set off the P0418 code when it notices a voltage signal from the SAI control circuit that is inconsistent with expectations.

What causes Code P0418?

  • Defective SAI pump relay
  • Difficulties with the wiring or connectors
  • Failure of the SAI pump
  • The fused SAI system blows.
  • A problem with the PCM, such as outdated software

What are the Symptoms of Code P0418?

Engine hesitancy when accelerating and stalling at startup and while idling are signs of this code. The secondary air injection system’s components making unusual noises is another sign of something wrong.

While there isn’t always a pressing need to fix the P0418 error, it is crucial to do so. Keep in mind that exhaust emissions contribute to air pollution. 

Symptoms of Code P0418

Steps to Diagnose for P0418

Because DTC P0418 is a generic powertrain code, it can be recorded on various cars. However, keep in mind that depending on the car you own, the methods for diagnosis and repair may change. For instance, the diagnostic steps for a P0418 code in a Toyota Tundra and a P0418 code in a VW Jetta may differ.

Bring your car to a professional to ensure the correct procedures are followed if you’re not yet confident in your DIY abilities.

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The mechanic needs a digital volt/ohmmeter and a sophisticated scanner to diagnose a P0418 fault code. The mechanic must additionally use this equipment and do the following actions when diagnosing:

  • Verify the one-way check valves are still functioning properly by inspecting them. To do this, the mechanic must remove the check valve and blow through it in both directions. The check valve should only allow one airflow direction if functioning properly.
  • Check for damage to any wiring, connectors, and components.
  • Examine each fitting and pipe in the secondary air injection system visually. Any cracking, breaking, or the mechanic should check for other damage.
  • Examine the secondary air injection system’s fuse panel. The mechanic can use the manufacturer’s service handbook to locate fuses.
  • Examine the secondary air injector pump for failure if the fuses continue to blow after being replaced.

If the code reappears, try clearing it and giving the car a test drive.

What to avoid when checking for Code P0418?

When changing a secondary air injection pump that has been broken, mechanics frequently forget to drain any extra water from the pump housing. 

As a result, the pump freezes when exposed to cold temperatures, binding up and failing again. 

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If a mechanic doesn’t check and replace a broken one-way check valve, moisture can build up, which causes the pump to malfunction once more when water permitted into the system freezes.

How serious is code P0418?

If this issue is not resolved before the cold winter arrives, the system’s water could freeze and bind the pump, leading to a failure. Higher emissions come from the concerned vehicle due to secondary air injection pump failure.

How to Fix P0418 code?

Fixing a P0418 error code is difficult, especially if you lack the necessary equipment and technical know-how. If you don’t have any experience working on exhaust systems or cars, you should take your car to the nearest shop and have a licensed mechanic work on it. 

Make sure you do your study and read the instructions before performing any repairs if you intend to handle the job yourself.

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If the wiring, connectors, or components of the secondary air injection system are determined to be flawed, the mechanic should carry out the following repairs to eliminate a P0418 trouble code:

  • If the one-way check valves are not operating properly, replace them.
  • Replace any wire or connectors that are faulty or damaged.
  • To prevent the secondary air injection system’s fuses from blowing again, replace those that have already done so.
  • If additional testing reveals that the secondary air injection pump is the problem, replace it.

Cost of repairing a P0418 issue

P0418 stands for “Secondary Air Injection System Relay A circuit Malfunction,” a diagnostic trouble code (DTC). Numerous things can cause this. Thus a mechanic must identify the precise cause in your case to clear the code. For $120, a licensed mechanic will perform a check engine light diagnostic at your house or place of business. In addition, you will receive an upfront estimate for the suggested fix.


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