Technical Description of OBD-II Trouble Code
Malfunction in the Circuit of Secondary Air Injection System Switching Valve A
What does that signify?
This diagnostic trouble code (DTC) is a generic powertrain code that is applicable to vehicles equipped with OBD-II. Although it is a generic code, the specific repair steps may vary depending on the make and model of the vehicle.
The Secondary Air Injection System (AIR) Switching Valve is a computer-controlled valve that regulates the injection of air into the engine’s exhaust system (this valve may be integrated with the AIR pump). This code pertains to a problem in the circuit of the SOLENOID, not the operation of the AIR pump itself.
The AIR injection system injects fresh air into the exhaust ports of a cold engine or the catalytic converter of a warm engine in order to reduce hydrocarbon emissions (HC), carbon monoxide (CO), and oxides of nitrogen (NOx). This process helps convert hydrocarbons into water vapor (H20) and carbon monoxide into carbon dioxide (CO2).
Typically, the electric air pump is the most common type, although there may be belt-driven air pumps with an electric clutch. The PCM (Powertrain Control Module) controls the electric air pump by grounding the AIR pump relay control circuit and supplying voltage to the AIR pump and solenoid valve (which may control a vacuum-operated shut-off valve or directly control air flow). There is a check valve in the fresh air supply tube that prevents exhaust gases from flowing back into the AIR pump.
The PCM monitors the driver that activates the AIR pump for faults. When the PCM commands the AIR pump relay to turn on, the voltage of the control circuit should naturally be close to zero. When the relay is commanded to turn off, the control circuit should have battery voltage present. If the PCM detects a voltage that is not as expected, it will trigger the P0412 code.
Other trouble codes related to the secondary air injection system include P0410, P0411, P0413, P0414, P0415, P0416, P0417, P0418, P0419, P041F, P044F, P0491, and P0492.
Symptoms
The symptoms of a P0412 DTC may include:
Causes
Possible causes of a P0412 code include:
Possible Solutions
If you have access to a scan tool, you can command the AIR pump solenoid on and off with the KOEO (Key On Engine Off) function. If the solenoid does not operate, unplug it and use a voltmeter to check for voltage when it is commanded on and also check for a good ground. If there is voltage and a good ground, inspect the connection at the solenoid wiring harness connector. If the connection is good, replace the solenoid. If there is no voltage supplied to the connector when commanding the solenoid on, locate the AIR pump relay and verify that there is fused battery voltage present at the switched side of the circuit that supplies voltage to the AIR pump. If there is no voltage, check for a blown fuse or an open in the wiring and repair it.
If battery voltage is present at the voltage feed side of the relay, a quick way to check the solenoid and AIR pump operation is to use a fused jumper to manually activate it. This can be done by jumpering battery voltage to the switched AIR pump voltage feed. Usually, this involves terminals 30 and 87 of the relay schematic (although not always). If the solenoid (and possibly the AIR pump) operates, it indicates that the wiring and solenoid are functioning properly. If it does not activate, inspect the wiring harness and locate any open or short in the voltage feed to the AIR pump solenoid and repair it. If jumpering the solenoid to battery voltage activates the solenoid, it is time to check for voltage on the PCM controlled side of the relay with KOEO. If there is no voltage, repair any open or short in the circuit and retest.
To check the PCM wiring of the AIR pump solenoid, grounding the control circuit that is normally operated by the PCM will determine if the wiring is intact. Grounding the circuit at the PCM connector with KOEO should activate the AIR pump relay, which in turn should activate the AIR pump and solenoid. If this does not work, there may be an open or short in the PCM control circuit. If grounding the control circuit activates the AIR pump and solenoid, verify that the PCM has good ground paths and no damage to the connector or water intrusion. If everything checks out, suspect an open driver in the PCM.
