Description of DTC code P0412

Vehicles are equipped with an air pump to reduce tailpipe emissions at start-up. This pump is activated through a relay, which is driven to the ground by the Powertrain Control Module (PCM). Also, the PCM grounds the vacuum control solenoid circuit of the air switching valve. Then, the vacuum is applied to both diaphragms of the switching valve, then they open the shut-off valve.

These circuits are enabled simultaneously when the Air Injection System (AIR) operation is required. Once the AIR system is working, the air pump makes it possible that fresh air comes into the exhaust stream, so catalyst operation is accelerated.

On the other hand, if the system is switched off, the shut-off valves will prevent airflow in either direction.

The OBDII DTC P0412 refers to a problem in the secondary air injection system switching valve control solenoid circuit. If the PCM observes an unexpected voltage, this code will be set.

Symptoms of fault code P0412

  • Check Engine light ON.
  • The injection system pump may not turn on.
  • The engine runs rich.
  • Tailpipe emissions have increased.

Causes of OBD2 P0412

Typical causes of the P0412 OBD2 fault code:

  • Open circuit in switching valve due to high voltage.
  • Low switching valve voltage indicates a short circuit.
  • Damage to the control circuit.
  • The power supply circuit from the battery to the relay may be shorted.
  • Short-circuit in the power supply from the battery to the relay.

Possible solutions of the DTC code P0412

The steps to troubleshoot problems caused by the P0412 OBDII diagnostic code are as follows:

  • Check the resistance of the air pump, as well as the air injection switching valve.
  • Check that the injection pump voltage is right between the power and ground pins.
  • Change the air injection valve.
  • Replace any wires that you notice are in poor condition.
  • Replace the air injection pump along with the power relay.

Codes related to P0412

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