Technical Description of OBD-II Trouble Code
Low Circuit for Intake Manifold Runner Control in Bank 2
What does that signify?
This diagnostic trouble code (DTC) is a generic powertrain code that is applicable to all vehicles manufactured from 1996 onwards (such as Nissan, Honda, Infiniti, Ford, Dodge, Acura, Toyota, etc.). Although it is a generic code, the specific repair steps may vary depending on the make and model of the vehicle.
Based on my experience, a stored code P2012 indicates that the powertrain control module (PCM) has detected a lower-than-expected voltage in the intake manifold air control (IMRC) actuator circuit for engine bank 2. Bank 2 refers to a malfunction related to the engine bank that does not contain the number one cylinder.
The PCM electronically controls the IMRC system, which is used to manage and fine-tune the flow of air into the lower intake manifold, cylinder heads, and combustion chambers. The IMRC system consists of specially shaped metal flaps that fit tightly into the intake manifold port of each cylinder. These flaps are opened and closed by an electronic runner control actuator. The flaps are secured to a metal rod that extends through the center of each intake port and is opened with one motion. If one of the flaps is stuck or binding, all of the flaps can become inoperative. The IMRC actuator is usually secured to the rod by a mechanical arm or gear, although some models use a vacuum diaphragm. When a vacuum-operated actuator is used, the PCM controls an electronic solenoid that regulates intake vacuum to the IMRC actuator.
Research has shown that creating a swirling effect in the air flow helps to atomize the air/fuel mixture more thoroughly. This thorough atomization helps to reduce exhaust emissions, improve fuel efficiency, and optimize engine performance.
Different manufacturers use varying IMRC methods to channel and restrict the air flow as it enters the engine. To understand the specific IMRC system in a particular vehicle, it is recommended to consult a reliable vehicle information source (such as All Data DIY). Typically, the IMRC runners are nearly closed during starting and idling conditions, and they are opened most of the way when the throttle plate is opened.
In order to ensure that the IMRC system is functioning as intended, the PCM monitors input data signals from various sensors, including the IMRC runner position sensor, manifold absolute pressure (MAP) sensor, manifold air temperature sensor, intake air temperature sensor, throttle position sensor, oxygen sensors, and mass airflow (MAF) sensor.
The PCM monitors the actual position of the runner flaps and adjusts it based on engine drivability data. If the PCM does not detect a significant change in MAP or manifold air temperature as expected, it may illuminate a malfunction indicator lamp and store a code P2012. In some cases, multiple failure cycles may be required for the malfunction indicator lamp to illuminate.
Symptoms
The symptoms of a P2012 code may include:
Causes
Possible causes for this engine code include:
Diagnostic and Repair Procedures
When attempting to diagnose a code P2012, it is recommended to use a diagnostic scanner, a digital volt/ohmmeter (DVOM), and a reliable vehicle information source. It is advisable to check technical service bulletins (TSB) for specific symptoms, stored codes, and the make and model of the vehicle before proceeding with any diagnosis. If a related TSB is found, the information can often assist in diagnosing the code, as TSBs are created based on numerous repairs.
A visual inspection of the system wiring and connector faces is a good starting point for diagnosis. It is important to note that IMRC actuator connectors are prone to corrosion, which can cause an open circuit. Therefore, attention should be focused on that area.
Next, the scanner should be connected to the vehicle diagnostic connector to retrieve all stored codes and freeze frame data. It is recommended to write down this information in case the code is intermittent. After that, the codes should be cleared and the vehicle should be test-driven to see if the code is reset.
If the code is reset, access to the IMRC actuator solenoid and IMRC runner position sensor should be gained. The vehicle information source should be consulted for testing specifications, and the DVOM should be used to perform resistance tests on both the solenoid and the sensor. If either of these components fails to comply with the specifications, it should be replaced and the system should be retested.
To prevent PCM damage, all related controllers should be disconnected before testing circuit resistance with the DVOM. If the actuator and sensor resistance levels comply with the manufacturer’s specifications, the DVOM should be used to test resistance and continuity on all system circuits. Any shorted or open circuits should be repaired or replaced as necessary.
Additional diagnostic notes:
