Technical Description of OBD-II Trouble Code
The circuit for the Input/Turbine Speed Sensor “B” is experiencing intermittent issues.
What does that mean?
This diagnostic trouble code (DTC) is a generic powertrain code that applies to all vehicles manufactured from 1996 onwards (Ford, Honda, Mazda, Mercedes, VW, etc.). While it is a generic code, the specific repair steps may vary depending on the make and model of the vehicle.
If you encounter trouble code P2768, it is likely because the powertrain control module (PCM) has detected an inconsistent voltage input signal from the circuit of the input (or turbine) speed sensor labeled as “B”. Although the input and turbine speed sensors serve the same purpose and are essentially the same, different manufacturers use different terminology for these components.
In most cases, the input/turbine speed sensor is a 3-wire, electromagnetic sensor used to monitor the transmission’s input speed in revolutions per minute (RPM). It is usually located near the rear of the bell housing, at the transmission input shaft, and secured with a bolt/stud or threaded directly into the transmission case.
A notched reluctor wheel or specially designed grooves are permanently attached to the transmission’s main (or input) shaft. As the engine runs and transfers RPMs to the transmission, the input shaft (or reluctor wheel) passes close to the sensor. The steel shaft (or reluctor wheel) completes an electronic/electromagnetic circuit with the sensor. When the grooved (or notched) areas pass by the sensor, the circuit is interrupted, creating an electronic pattern. The PCM recognizes this pattern as a waveform that it interprets as the transmission’s input/turbine speed.
Various factors such as transmission output speed, engine speed, throttle position, percentage of engine load, and others are compared and calculated to determine the desired input/turbine RPM speed. If the input/turbine speed or system circuit voltage deviates from the predetermined degree of accuracy for a specific amount of time, a code P2768 will be stored (and a malfunction lamp may illuminate).
The P2768 code indicates an intermittent input circuit voltage issue for the input/turbine speed sensor.
Symptoms
The symptoms associated with a P2768 code may include:
Causes
Possible causes for this code to be set are:
Diagnostic and Repair Procedures
It is always a good idea to check for technical service bulletins (TSB) specific to your vehicle. There may be a known issue with a known fix provided by the manufacturer, which can save time and money during diagnosis.
To diagnose the P2768 code correctly, you will need a digital volt/ohmmeter (DVOM), a manufacturer’s service manual, an advanced diagnostic scanner, and possibly an oscilloscope.
Start by visually inspecting the system wiring and connectors. Repair any obvious shorted or open circuits and/or connectors before proceeding. Also, inspect the battery, battery cables, cable ends, and test the alternator output.
Next, connect the scanner to the diagnostic port and retrieve all stored codes. Write them down for future reference and make note of the freeze frame data.
Use the scanner data stream to identify the malfunctioning circuit if there are input sensor and output sensor codes present. Narrow down the data stream to include only relevant information for the most accurate data.
Metal debris on the magnetic contacts of the input and/or output speed sensors can cause intermittent or erratic sensor output data. Remove the sensor and check for metallic debris. Clean excessive debris from the magnetic surfaces before reinstalling. Also, inspect the interruption grooves and/or reluctor wheel notches for signs of damage or wear.
Use the DVOM to test the resistance and circuit voltage of individual sensors following the manufacturer’s guidelines. Replace sensors that do not comply with the manufacturer’s specifications.
When testing resistance or continuity with the DVOM, disconnect all related controllers to avoid controller failure.
If all system circuits and sensors are in proper working order and comply with the manufacturer’s specifications, suspect a faulty PCM or a PCM programming error if code P2768 is stored.
Additional diagnostic notes:
