Technical Description of OBD-II Trouble Code
Performance Issue with Internal Control Module Knock Sensor Processor 2
What does that signify?
This generic powertrain diagnostic trouble code (DTC) is commonly found in many OBD-II vehicles, including Chevrolet, Subaru, Ford, Mazda, BMW, Peugeot, and others.
When code P06B7 is stored, it indicates that the powertrain control module (PCM) has detected a performance error in the internal processor of a specific knock sensor (designated as 2). Other controllers may also detect a performance error in the PCM’s knock sensor circuit, resulting in the storage of code P06B7.
The knock sensor is typically threaded directly into the engine block and functions as a piezoelectric sensor. Its location may vary among manufacturers, but most are positioned on the sides of the block (between water jacket freeze plugs) or in the valley beneath the intake manifold. Knock sensors located on the sides of the engine block are often threaded into engine coolant passages, so caution must be exercised when removing them to avoid burns from hot coolant. It is important to allow the engine to cool and properly dispose of coolant before removing any knock sensor/s.
The knock sensor contains a piezoelectric sensing crystal that generates a small amount of voltage when shaken or vibrated. Since the knock sensor control circuit is typically a one-wire circuit, the PCM interprets the voltage generated by the vibration as engine noise or vibration. The severity of the vibration experienced by the piezoelectric crystal determines the level of voltage produced in the circuit.
If the PCM detects knock sensor voltage indicative of engine knock or severe spark detonation, it may retard ignition timing and store a knock sensor control code.
A small amount of voltage is always produced by the knock sensor when the engine is running, as some vibration is inevitable regardless of how smoothly the engine operates.
Internal control module monitoring processors are responsible for various self-test duties and overall accountability of the internal control module. The knock sensor input and output signals undergo constant monitoring by the PCM and other related controllers, including the transmission control module (TCM), traction control module (TCSM), and others.
Whenever the ignition is on and the PCM is energized, self-tests for the knock sensor system are initiated. In addition to running internal controller self-tests, the controller area network (CAN) compares signals from each individual module to ensure proper functioning of each controller. These tests are performed simultaneously.
If the PCM detects an internal discrepancy in the knock sensor processor or a problem between any of the on-board controllers indicating an internal knock sensor system error, code P06B7 will be stored and the malfunction indicator lamp (MIL) may illuminate. The number of failure cycles required for MIL illumination depends on the perceived severity of the malfunction.
Example photo of a PCM:
What is the severity of this DTC?
Codes related to internal control module processors should be considered severe, as a stored code P06B7 can lead to various drivability concerns.
What are some of the symptoms of the code?
Symptoms of a P06B7 trouble code may include:
What are some of the common causes of the code?
Possible causes for this code include:
What are some P06B7 troubleshooting steps?
Diagnosing a code P06B7 can be challenging, even for experienced technicians. Reprogramming may also be necessary, and without the proper equipment, replacing a defective controller and completing a successful repair will be impossible.
If there are ECM/PCM power supply codes present, they must be addressed before attempting to diagnose a P06B7.
Prior to declaring any controller defective, several preliminary tests can be performed. These tests require a diagnostic scanner, a digital volt/ohmmeter (DVOM), and reliable vehicle information.
Connect the scanner to the vehicle diagnostic port and retrieve all stored codes and freeze frame data. It is important to record this information in case the code is intermittent. After recording the necessary information, clear the codes and test drive the vehicle until the code is reset or the PCM enters readiness mode. If the PCM enters readiness mode, the code is intermittent and will be more difficult to diagnose. In some cases, the condition that caused the P06B7 to be stored may need to worsen before a diagnosis can be made. If the code is reset, proceed with the following preliminary tests.
When diagnosing a P06B7, information is crucial. Search for technical service bulletins (TSB) that match the stored code, vehicle (year, make, model, and engine), and exhibited symptoms. The right TSB may provide diagnostic information that greatly assists in the diagnosis.
Use the vehicle information source to obtain connector face views, connector pin-out charts, component locators, wiring diagrams, and diagnostic flow charts related to the code and vehicle in question.
Use the DVOM to test controller power supply fuses and relays. Replace blown fuses as necessary. Fuses should be tested with the circuit loaded.
If all fuses and relays appear to be functioning properly, visually inspect the controller-related wiring and harnesses. Also check chassis and engine ground junctions. Use the vehicle information source to locate ground locations for related circuits and test ground integrity using the DVOM.
Inspect system controllers for signs of water, heat, or collision damage. Any damaged controller, especially due to water exposure, should be considered defective.
If controller power and ground circuits are intact, suspect a defective controller or a controller programming error. Controller replacement will require reprogramming. Aftermarket sources may offer reprogrammed controllers for some vehicles, while others may require on-board reprogramming that can only be done through a dealership or qualified source.
