Error Code P1423 is defined as Secondary Air Injection System Bank 1 Insufficient Flow Detected. This indicates a problem with the secondary system.

This error code is a manufacturer-specific trouble code, meaning it does not apply to all vehicles makes. Rather, it applies only to specific vehicle makes, such as Toyota. Specification on the definition, troubleshooting, and repairs still vary from one make and model to another.


This trouble code is a diagnosis code which suggests a leak is detected in the EVAP (evaporative emission system) purge line using engine intake manifold vacuum. If the pressure doesn’t increase, the PCM (powertrain control module, also known as ECM or engine control module in other vehicle makes) will check for leaks in the line between the fuel tank and the EVAP canister purge volume control solenoid valve under the following vacuum conditions.

To clear the line between the fuel tank and the EVAP canister purge volume control solenoid valve, the vacuum cut valve bypass valve is opened. The former will then be closed to shut the EVAP purge line off. Using the intake manifold vacuum, the EVAP canister purge volume control solenoid valve is opened to depressurize the EVAP purge line. After implementing the depressurization, the EVAP canister purge volume control solenoid valve will close.

The secondary air system works during a cold start to help the catalytic converter reach its operating temperature faster, which then results in a cleaner burn.

Common Symptoms

As with other error codes, this code activates the Check Engine light and registers the code to the system. In many cases, fuel odor caused by released fuel vapors may also be noticed.

In some cases though, the vehicle may not exhibit noticeable symptoms, but it’s important to have the code addressed.

Possible Causes

Many factors can contribute to this error, some of the common causes are:

  • Defective EVAP Purge solenoid
  • Loose or missing fuel cap
  • Wrong fuel filler cap used
  • Fuel filler cap remains open or fails to close
  • Foreign matter caught in fuel filler cap
  • EVAP canister leaks
  • Fuel tank leaks

How to Check

To check, inspect the area for broken or cracked hoses. If hoses are in good shape, then the problem must be with the secondary air pump or solenoid.

How to Fix

Replace secondary air pump or solenoid

Fix canister or fuel tank leaks

Place fuel cap tightly

Use the right fuel filler cap

Secondary air system does not affect the performance of the engine; it keeps the emission lower during cold start of the engine.