B1278 – OBD-II DTC

OBD-II DTC B1278 – Servo Motor Potentiometer Foot Circuit Short To Battery

DTC B1278 meaning

DTC B1278 refers to a diagnostic trouble code indicating a problem with the servo motor potentiometer foot circuit. This code specifically points to a short circuit to battery voltage within the potentiometer circuit, which is responsible for measuring the position of the accelerator pedal or throttle input. When this circuit experiences a short, it can lead to incorrect readings and affect the vehicle’s performance and safety systems.

DTC B1278 symptoms

Common symptoms associated with DTC B1278 may include:

• Illumination of the check engine light
• Unresponsive or erratic throttle response
• Reduced engine power or limp mode activation
• Increased fuel consumption
• Difficulty in accelerating

DTC B1278 causes

Several factors can lead to the occurrence of DTC B1278, including:

• Faulty servo motor potentiometer
• Wiring issues, such as frayed or damaged wires
• Corrosion or poor connections in the electrical circuit
• Short circuit in the potentiometer circuit
• Faulty engine control module (ECM) or powertrain control module (PCM)

DTC B1278 seriousness

The seriousness of DTC B1278 can vary based on the symptoms experienced. It is generally considered a moderate to serious issue because:

• It can lead to unsafe driving conditions due to erratic throttle response.
• It may cause the vehicle to enter limp mode, limiting performance.
• Ignoring the issue can lead to further damage to the engine or transmission.

How to diagnose DTC B1278

To diagnose DTC B1278, follow these steps:

1. Use an OBD-II scanner to confirm the presence of DTC B1278.
2. Inspect the wiring and connectors related to the servo motor potentiometer for damage or corrosion.
3. Check the potentiometer for proper operation using a multimeter.
4. Test the voltage supply to the potentiometer circuit.
5. Examine the ECM/PCM for any faults or updates.

How to fix DTC B1278 step-by-step instructions

To fix DTC B1278, follow these steps:

1. Repair or replace any damaged wiring or connectors found during diagnosis.
2. Replace the faulty servo motor potentiometer if it is not functioning correctly.
3. Ensure all connections are clean and secure to prevent future issues.
4. Clear the DTC using an OBD-II scanner.
5. Test drive the vehicle to ensure the issue is resolved and the check engine light does not reappear.

How to erase DTC B1278

To erase DTC B1278, follow these steps:

1. Connect an OBD-II scanner to the vehicle’s diagnostic port.
2. Turn on the ignition without starting the engine.
3. Navigate to the DTC menu on the scanner.
4. Select the option to clear or erase trouble codes.
5. Confirm the action and wait for the scanner to complete the process.
6. Disconnect the scanner and start the vehicle to verify that the code does not return.