What Does It Mean?
This generic powertrain diagnostic trouble code (DTC) generally applies to many OBD-II vehicles. This may include, but is not limited to, vehicles from Ford, Mazda, etc.
When a P06B8 code is stored, it means the Powertrain Control Module (PCM) has detected an internal processor performance error with non-volatile random access memory (NVRAM). Other controllers may also detect an internal PCM performance error (with NVRAM) and cause a P06B8 to be stored.
The internal control module monitoring processors are responsible for various controller self-test tasks and the overall responsibility of the internal control module. The NVRAM input and output signals are subjected to self-test and are continuously monitored by the PCM and other associated controllers. The Transmission Control Module (TCM), Traction Control System Module (TCSM), and other controllers also interact with the NVRAM.
In automotive applications, NVRAM is used to help retain data memory when the PCM is turned off. The NVRAM is integrated into the PCM. Even though NVRAM is capable of over a million programming changes and is designed to last for hundreds of years, it can be sensitive to excessive heat and humidity.
Whenever the ignition is turned on and the PCM is powered up, the NVRAM self-tests are initiated. In addition to running internal controller self-tests, the Controller Area Network (CAN) also compares the signals from each individual module to ensure each controller is functioning correctly. These tests are performed simultaneously.
If the PCM detects an internal anomaly in the NVRAM processor, a P06B8 code will be logged and a Malfunction Indicator Lamp (MIL) may be illuminated. Additionally, if the PCM detects a problem between any of the onboard controllers, which would indicate an internal knock sensor system error, a P06B8 code will be stored and a Malfunction Indicator Lamp (MIL) may be illuminated. Multiple failure cycles may be required for MIL illumination, depending on the perceived severity of the malfunction.
How Severe Is This DTC?
Internal control module processor codes should be classified as severe. A stored P06B8 code can lead to various driving issues.
What Are Some of the Symptoms of the Code?
Symptoms of a P06B8 trouble code may include:
A variety of engine driving symptoms
Other stored diagnostic trouble codes
What Are Some of the Common Causes of the Code?
Causes
of this code may include:
Faulty PCM or PCM programming error
Open or shorted circuit or connectors in the CAN harness
Insufficient control module ground
What Are the P06B8 Troubleshooting Steps?
Even for the most experienced and well-equipped professional technician, diagnosing a P06B8 code can prove very challenging. There is also the issue of reprogramming. Without the necessary reprogramming equipment, it will be impossible to replace a faulty controller and perform a successful repair.
If ECM/PCM power codes are present, they will obviously need to be corrected before attempting to diagnose a P06B8.
There are several preliminary tests that can be performed before declaring a controller faulty. A diagnostic scanner, a digital volt/ohmmeter (DVOM), and a reliable vehicle information source will be necessary.
Connect the scanner to the vehicle’s diagnostic port and retrieve all stored codes and freeze frame data. You will want to note this information, just in case the code proves to be intermittent. After recording all relevant information, clear the codes and test drive the vehicle until the code resets or the PCM enters readiness mode. If the PCM enters readiness mode, the code is intermittent and will be more difficult to diagnose. The condition that caused the P06B8 to be stored may even need to worsen before a diagnosis can be made. If the code resets, continue with this short list of preliminary tests.
When trying to diagnose a P06B8, information can be your best tool. Search your vehicle information source for Technical Service Bulletins (TSBs) that match the stored code, the vehicle (year, make, model, and engine), and the symptoms presented. If you find the right TSB, it may provide diagnostic information that will assist you significantly.
Use your vehicle information source to obtain connector face views, connector pinout diagrams, component locators, wiring schematics, and diagnostic flowcharts related to the code and vehicle in question.
Use the DVOM to test the controller’s power fuses and relays. Test and replace blown fuses as needed. Fuses should be tested with the circuit loaded.
If all fuses and relays appear to be functioning as expected, a visual inspection of the wiring and harnesses related to the controller is necessary. You will also want to check the chassis and engine ground junctions. Use your vehicle information source to obtain ground locations for the related circuits. Use the DVOM to test ground integrity.
Visually inspect the system controllers for signs of water, heat, or collision damage. Any damaged controller, especially by water, should be considered faulty.
If the controller’s power and ground circuits are intact, suspect a faulty controller or a controller programming error. Replacing the controller will require reprogramming. In some cases, you can purchase pre-programmed controllers through aftermarket sources. Other vehicles/controllers will require onboard reprogramming that can only be performed by a dealership or other qualified source.
Unlike most other codes, P06B8 is likely caused by a faulty controller or a controller programming error
Test the system ground integrity by connecting the DVOM’s negative test lead to ground and the positive test lead to battery voltage