Error Code P06B8 is defined as Internal Control Module Non-Volatile Random Access Memory (NVRAM) Error. This is a generic trouble code, meaning it applies to all vehicles equipped with the OBD-II system, especially those made since 1996 up to present. This includes vehicle models from but not limited to, Ford, Mazda, etc. Specifications on the definition, troubleshooting, and repairs, of course, vary from one make and model, and powertrain configuration.
The Internal control module monitoring processors are the ones responsible for the self-test duties of various controllers, as well as overall internal control module accountability. Both the TPS/APP sensor input and output signals are subjected to self-test and constantly being monitored by the PCM and other related controllers. The TCM (transmission control module), TCSM (traction control module), and other controllers are subject to the interaction with the TPS/APP sensor.
When Error Code P06B8 is stored, this means that the PCM (powertrain control module also known as ECM or engine control module in other vehicle makes) has detected an error in the internal processor performance with NVRAM (non-volatile access memory). Other controllers may also detect an internal PCM performance error (with NVRAM) and cause Error Code P06B8 to be stored.
For automotive applications, the NVRAM is used to help keep data memory when the power is shut off to the PCM. It is integrated right into the PCM. Though the NVRAM is designed to last for decades, it can be susceptible to damage from excessive moisture and heat.
Every time the ignition is turned on, the PCM energizes the NVRAM to initiate the self-test. Aside from running the internal controller self-tests, the CAN (controller area network) also compares signals from each individual module to ensure each controller is working correctly. These tests are simultaneously performed.
If the PCM sees an internal discrepancy in the NVRAM processor, then the Error Code P06B8 will be stored, and simultaneously activate the check engine light. Additionally, if the PCM detects a problem between the onboard controller, which indicates an internal knock sensor system error, then this code will be stored as well.
In some cases, multiple drive cycles may be necessary before this code gets stored. This depends on the severity of the problem.
- Variety of drivability symptoms
Other diagnostic codes may be present as well.
- Damaged or programming error in the PCM
- Insufficient control module ground
- Open or shorted circuit or connectors in CAN harness
How to Check
This code is one of the tricky codes to diagnose. To make matters more difficult, it could also be a result of the reprogramming issue. Without the right reprogramming equipment, it will be impossible to replace a defective controller and complete the repair.
When diagnosing this code, it’s important to diagnose and repair other related codes first.
There are many preliminary tests before you can declare any defective controller. You’ll need a diagnostic scanner, DVOM (digital volt-ohmmeter), and a reliable vehicle information source.
Then, connect the scanner to the vehicle’s diagnostic port to retrieve all stored codes, including their freeze frame data. Take note of this information in case the problem is proven to be intermittent. Clear the codes then take the vehicle for a test drive. One of the two things can happen; either the code is restored, or the PCM enters readiness mode.
If the code enters readiness mode, then the problem is intermittent. Meaning, you would have to wait for the problem to worsen before you can accurately diagnose it. If the code is restored, however, then you can continue on your diagnosis.
Search for the TSB (technical service bulletins) that replicates the code, vehicle (year, make, model, and engine), and symptoms for the problem. You can find this information from the vehicle information source.
Then, get the face views, connector pinout charts, wiring diagrams, component locators, and diagnostic flow charts of the code for the vehicle in question.
Test the controller power supply fuses and relays using the DVOM. Replace any blown fuses, fusible links, and relays as necessary. To avoid misdiagnosis, fuses must be tested with the circuit loaded.
If fuses and relays appear to be functioning as intended, then proceed on inspecting the controller related wiring and harness (in that order). Also, make sure you check the chassis and engine ground junctions. Get the ground locations for related circuits using the vehicle information source. Then, test the ground integrity using the DVOM.
Make sure you inspect the system controllers for signs of water damage, heat, or collision damage. Any controllers with signs of damage must be considered defective and must be replaced.
If controller power and ground circuits are intact, then you can suspect a defective or programming error in the controller. This means the controller must be reprogrammed. In many cases, you can purchase reprogrammed controllers from aftermarket sources. Some vehicle/controllers require on-board reprogramming that can only be done in the dealership or another qualified source.
How to Fix
Depending on the diagnosis, common repairs for this code include:
- Repair or replacement of burnt, or damaged wirings or connectors
- Replacement of blown fuses, relays, or fusible links
- Repair of open or shorted circuit or connector in the CAN harness
- Replacement and reprogramming of PCM
This error code is categorized as severe and can result in a variety of drivability concerns.
Unlike many codes, this error code is likely caused by a defective or programming error in the controller.
Connect DVOM’s negative test lead to ground, and the positive test lead to battery voltage to test the ground integrity.