P2259 Code: Secondary Air Injection System Control “B” Circuit Low

The secondary air injection (SAI) system pumps fresh air into the exhaust manifold or inside the catalytic converter to assist in the oxidizing process. The system helps reduce highly rich exhaust emissions from escaping into the atmosphere. If the powertrain control module detects an issue with the SAI system, a P2257 code will be logged by on-board diagnostics (OBD).

What Does the P2259 Code Mean?

Diagnostic trouble code (DTC) P2259 stands for “Secondary Air Injection System Control ‘B’ Circuit Low.”

The SAI system has a belt-driven or electrically driven air pump mounted at the front of the engine. During cold engine startup in a typical SAI system, the pump directs airflow to the exhaust manifolds where it passes through one-way check valves. This keeps exhaust gases away from the switching solenoids and pump.

Once the engine is warmed up and achieves a closed loop, the air pump will direct airflow to the catalytic converter.

If the PCM detects that the actual and desired states of the SAI control circuit do not match, it may set code P2259 in memory.

Note: The definition of code P2259 might be different depending on the vehicle manufacturer. Consult the appropriate repair manual or repair database for the exact code definition.

What are the Common Causes of the P2259 Code?

• Clogged or disconnected vacuum hose
• Secondary air pump failure
• Secondary air pump relay failure
• Faulty SAI valve
• Wiring issues
• Powertrain control module failure

What are the Common Symptoms of the P2259 Code?

• Illuminated check engine light
• Disabled secondary air injection system

How to Diagnose the P2259 Code

DTC P2259 is a generic powertrain code that can be logged in vehicles with an OBD-II system. While this might be the case, keep in mind that your vehicle’s specifications can affect the diagnostic process.

Diagnosing this trouble code might require you to use a scan tool and inspect the affected system for signs of damage. If you’re not familiar with how the process works, you can always have a certified mechanic do the job for you. Otherwise, you can go ahead and do it yourself.

To help you out, here’s a short clip that shows what the process might involve.

How to Fix the P2259 Code

Without the right tools and technical knowledge, resolving a P2259 code can be tricky and frustrating. It can even lead to complex and expensive repairs if done incorrectly. If you’re not confident with your DIY skills yet, it’s best to bring your vehicle to the nearest auto repair shop and let the pros handle the job for you.

But if you’ve had some experience in dealing with DTCs before, then you already know that there’s no magic fix that will work on all makes and models. Having the right manual is critical in ensuring a successful repair job, which is why you might want to look at vehicle-specific guides like those from Chilton or an ALLDATA subscription before you begin.