Technical Description of OBD-II Trouble Code
Performance Issue with Internal Control Module Knock Sensor Processor 1
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 P06B6 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 1) circuit. Other controllers may also detect an internal PCM performance error in the knock sensor circuit, resulting in the storage of code P06B6.
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. It is important to exercise caution when removing these sensors, as hot coolant can cause severe burns. Prior to removing any knock sensor/s, allow the engine to cool and dispose of coolant properly.
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 recognizes the voltage generated by the vibration as engine noise or vibration. The severity of the vibration experienced by the piezoelectric crystal inside the knock sensor determines the level of voltage produced in the circuit.
If the PCM detects a level of 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. The knock sensor system also interacts with the transmission control module (TCM), traction control module (TCSM), and other controllers.
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, it stores code P06B6 and may illuminate the malfunction indicator lamp (MIL). Additionally, if the PCM detects a problem between any of the on-board controllers, indicating an internal knock sensor system error, it stores code P06B6 and may illuminate the MIL. Depending on the perceived severity of the malfunction, multiple failure cycles may be necessary for MIL illumination.
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 P06B6 can lead to various drivability concerns.
What are some of the symptoms of the code?
Symptoms of a P06B6 trouble code may include:
What are some of the common causes of the code?
Possible causes for this code include:
What are some P06B6 troubleshooting steps?
Diagnosing a code P06B6 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 P06B6.
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 P06B6 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 P06B6, information is crucial. Search your vehicle information source 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 your 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. Test and 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 wiring and harnesses related to the controller. Also check chassis and engine ground junctions. Use your vehicle information source to locate ground locations for related circuits. Use the DVOM to test ground integrity.
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. In some cases, reprogrammed controllers may be available through aftermarket sources. Other vehicles/controllers will require on-board reprogramming, which can only be done by a dealership or other qualified source.
