P06B4 Low indicator of the power supply circuit of the sensor B

P06B4 Low indicator of the power supply circuit of the sensor B

OBD-II DTC Datasheet

Low signal level in the power supply circuit B of the sensor

What does this mean?

This is a generic Diagnostic Trouble Code (DTC) applicable to many OBD-II vehicles (1996 and newer). This may include, but is not limited to, Buick, Chevrolet, Chrysler, Fiat, Ford, GMC, Mercedes-Benz, etc. Despite the general nature, the exact repair steps may vary depending on the year of manufacture, make, model and transmission configuration.

When the OBD-II equipped vehicle has stored the P06B4 code, it means the powertrain control module (PCM) has detected a low voltage condition for a specific sensor or sensor group. Depending on the manufacturer. The sensor (s) in question may be associated with an EGR system, a heated exhaust oxygen sensor system, an automatic transmission, or a transfer case (for AWD or AWD vehicles only). the victim is designated B (can also be swapped between A and B).

Most OBD-II sensors are activated by a voltage signal that is supplied by the PCM or one of the other on-board controllers. The amount of voltage applied (often called the reference voltage) can range from a very low voltage (usually measured in millivolts) to the full voltage of the battery. Most often, the sensor voltage signal is 5 volts; then the battery voltage follows. Obviously, you will need to determine exactly which sensor is associated with this code. This information will be provided by a reliable source of vehicle information.

If the PCM (or any of the other on-board controllers) detects a voltage level lower than expected on the power supply circuit indicated by B, a code P06B4 may be stored and the soon service / engine malfunction indicator lamp (SES / MIL) is illuminated. SES / MIL illumination may require multiple ignition failures.

Typical PCM Powertrain Control Module disclosed:

What is the severity of this DTC?

I would definitely call this code serious. Its wide sensor inclusion makes it difficult - if not impossible - to pinpoint exactly how catastrophic the symptoms of the condition that contributed to the P06B4 code could be.

What are some of the symptoms of the code?

Symptoms of a P06B4 trouble code may include:

• Transfer case does not work
• Engine start inhibit state
• Reduced fuel efficiency
• Engine wobble, sag, slip, or stumble
• Serious engine handling problems
• Transmission may shift unevenly
• Gearbox may shift abruptly

What are some of the common causes for the code?

Reasons for this code may include:

• Defective engine, transmission or transfer case sensor
• Blown fuse or fuse
• Open or short circuit in wiring and / or connectors or ground
• PCM error or PCM programming error

What are some steps to troubleshoot the P06B4?

Diagnose and repair any other codes associated with the sensor before attempting to diagnose a stored P06B4.

To accurately diagnose the P06B4 code, you will need a diagnostic scanner, a digital volt / ohmmeter (DVOM), and a source of reliable vehicle information.

Without the means to reprogram the controllers, obtaining an accurate diagnostic conclusion for a stored P06B4 will be challenging at best. You can save yourself a headache by searching for Technical Service Bulletins (TSBs) that reproduce the stored code, vehicle (year, make, model, and engine), and symptoms found. This information can be found in your vehicle information source. If you can find the appropriate TSB, it can provide very useful diagnostic information.

Connect the scanner to the vehicle diagnostic port and get all stored codes and corresponding freeze frame data. After you write down this information (in case the code turns out to be intermittent), clear the codes and test drive the vehicle. One of two things will happen; the code will be restored or the PCM will enter ready mode.

If the PCM enters ready mode (code intermittent), the code may be more difficult to diagnose. The condition that led to the persistence of P06B4 may need to worsen before an accurate diagnostic conclusion can be drawn. However, if the code is restored, continue with the diagnosis.

Get connector views, connector pinout diagrams, component locators, wiring diagrams, and diagnostic block diagrams (pertaining to the code and the vehicle in question) using your vehicle information source.

Visually inspect all associated wiring and connectors. Cut, burnt, or damaged wiring must be repaired or replaced. You can also check the chassis and engine grounding and make any necessary repairs before proceeding. Use your vehicle's source of information (power supply and ground locations) for information on ground connections for associated circuits.

If no other codes are stored and P06B4 continues to reset, use the DVOM to test the controller's power supply fuses and relays. Replace blown fuses, relays and fuses as necessary. Fuses should always be checked with a loaded circuit to avoid misdiagnosis.

You may suspect a faulty controller or a controller programming error if all controller power (input) and ground circuits are intact and insufficient sensor supply voltage is output from the PCM (or other controller). Please note that replacing the controller will require reprogramming. Reprogrammed controllers for some applications may be available in the aftermarket; other vehicles / controllers will require onboard reprogramming, which can only be done through a dealership or other qualified source.

Visually inspect the system controllers for signs of water, heat, or collision damage and suspect any controller that shows signs of damage is defective.

• The term "open" can be replaced with "disabled or disabled, cut or broken".
• The increased sensor supply voltage is likely the result of a short to battery voltage.

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