Guide To P077B OBD Error Code Solutions

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Have you ever seen a direction error in your vehicle? Do you know why the P077B error code keeps coming up? This is a general type of error code which appears in most of the vehicle but it has few exceptions. If the P077B error code is present in your vehicle, then it means that the powertrain control module or the hybrid control module has found a directional error in the output speed sensor.

If the error code appears, then the power control module has found that the output speed sensor is moving in wrong direction. If the signal of voltage is negative, PCM imagines that the reluctor ring is moving in wrong path. The PCM will also receive the input speed data of the vehicle and wheel. On comparison, the PCM can identify, if the reluctor ring is moving in right path. The negative speed sensor can appear due to mechanical problem or malfunctioning of the electronic system.

What causes this problem with the Output Speed Sensor Circuit - Direction Error?

• Defective or broken output speed sensor.
• Presence of debris in the output speed sensor.
• The circuits or connectors of the output speed sensor is shorted or open.
• Worn out or defective reluctor rings.
• Mechanical transmission faults.

1. Transmission Control Module - A faulty or broken TCM needs immediate replacement to avoid P077B error.
2. Shaft Speed Sensor - Inspect this element for leaks or damages and replace them to avoid further troubles.
3. Engine Control Module - Is your Engine Control Module broken? Get the right replacement part from Parts Avatar to avoid P077B error code
4. Speedometer/Odometer - A broken or damaged speedometer/ odometer must be replaced to show proper readings.

Have you ever wondered why it’s so important to know the symptoms of the problem? Well, it is extremely essential to know the symptoms of the problem in order to detect it. Keeping this in mind, let’s throw some light on few common symptoms of OBD error code P077B.

Common Symptoms

• The operation of speedometer/ odometer is erratic.
• Shift pattern of the transmission is unusual.
• Transmission engages delayed or slips.
• Codes related to transmission and ABS is stored.

After understanding the symptoms and few common causes behind the OBD error code, we are here to help you out in understanding the ways and means to correct the issue. You will need to undergo the following replacements:

• Replacing the output speed sensors.
• Replacing the circuits.
• Changing the connectors and reluctor rings.

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It is essential to diagnose this fault code. Here are some steps which a mechanic should follow for diagnosing the problem that triggered a P077B code to be stored:

• Use a reluctor ring for inspection and if it has damages or broken, then it must be your problem. Check for other symptoms in the automatic transmission fluid as they must be clean with no bad smell. If the transmission fluid is not up to the level as specified, the fill them and check for leaks, before proceeding further diagnosis.
• Use a scanner which has oscilloscope, DVOM and a dependable source of information in order to diagnose the P077B code.
• Retrieve all codes and freeze frame data by connecting a scanner to the vehicle. Before you proceed with diagnosis, write down the data, as it can help you down the right path.
• Obtain the correct vehicle information source with the help of a technical service bulletin. A TSB can help you with speed and correct diagnosis if it matches with the symptoms and stored error codes.
• As you test drive the vehicle, use a scanner data and obtain the output speed. If you narrow down to display specific fields, the speed and accuracy of data delivery will increase. The wires, connectors and sensors will be defective if there is incorrect signal from the sensors.
• Perform a resistant test with a DVOM and output speed sensor must be separated. The information source of your vehicle will have wiring diagrams, connector views and pinouts, and preferred test procedures. If the output of the speed sensor fails to match with the specifications, then it is damaged.
• Use an oscilloscope and get the live data from the output speed sensor. Check the output speed sensors signal and ground wire. This type of testing needs the vehicle to be lifted. Once the drive wheels of the vehicle are safety lifted, you have to run the drivetrain as you keep checking for the waveform pattern in the oscilloscope.
• Before you proceed continuity test with a DVOM, you must disconnect the connectors and its related connectors as it may damage the controllers.

Common Mistakes When Diagnosing the P077B Code

• High voltage in the control module.
• The speed sensor of the output shaft fails.
• Issues with cables.

P077A - Output Speed Sensor Circuit - Loss of Direction Signal