Technical Description of OBD-II Trouble Code
Excessive Clutch B Slippage
What does that signify?
This diagnostic trouble code (DTC) is a generic powertrain code that is applicable to many OBD-II vehicles (1996-newer). This includes vehicles from Volkswagen, Porsche, Honda, Audi, Acura, and others. While it is a generic code, the specific repair steps may vary depending on the year, make, model, and powertrain configuration.
If your vehicle has stored a code P081E, it means that the powertrain control module (PCM) has received a data input signal from the input and output speed sensors indicating excessive clutch slippage. The designation “clutch B” indicates that the vehicle is equipped with a clutch (pedal) position sensor (CPPS) that functions similarly to a throttle position sensor (TPS).
The transmission control module (TCM) may be a standalone unit, but it is commonly integrated into a single housing with the engine control module (ECM), known as the PCM.
The PCM uses input signals from various engine and transmission sensors to calculate the maximum allowable degree of transmission (clutch) slippage. Excessive clutch slippage can occur due to wear on the clutch disc and pressure plate, as well as mechanical failure. Discrepancies in CPPS voltage can also result in a stored P081E code. The PCM uses voltage input signals from the transmission input speed sensor, transmission output speed sensor, and the position of the clutch pedal to determine if the clutch is functioning within the parameters for maximum allowable slippage.
Typically, when the friction material on the clutch disc is worn down below a certain level, the clutch starts to slip. This condition is often accompanied by the distinct odor of burnt friction material.
If the PCM detects a degree of transmission (clutch) slippage that exceeds the maximum allowable parameters, a code P081E may be stored and the malfunction indicator lamp (MIL) may illuminate. Multiple ignition cycles (with a failure) may be required for MIL illumination.
What is the severity of this DTC?
A stored code P081E indicates that either a serious electrical issue or some type of clutch failure has occurred. In any case, it is important to rectify the conditions that led to the storage of this code as quickly as possible.
What are some of the symptoms of the code?
Symptoms of a P081E trouble code may include:
What are some of the common causes of the code?
Causes for this code may include:
What are some P081E troubleshooting steps?
Before attempting to diagnose a P081E, ensure that the clutch, pressure plate, and throwout bearing are functioning properly. Also, check the clutch arms and bushings, as well as the clutch hydraulics if applicable.
To diagnose a code P081E, you will need a diagnostic scanner, a digital volt/ohmmeter (DVOM), and a source of vehicle-specific diagnostic information. An oscilloscope may also be helpful for diagnosing input and output speed sensor malfunctions. CPPS output voltage can be monitored using the DVOM or oscilloscope, with the latter being more effective for detecting voltage spikes and glitches.
You can consult your vehicle information source to find a technical service bulletin (TSB) that matches the vehicle’s year, make, and model, as well as the engine size, stored codes, and exhibited symptoms. If you find one, it may provide helpful diagnostic information.
Once you have confirmed that the clutch is functioning properly, proceed with the first step of the diagnosis.
Step 1
Use the scanner (connected to the vehicle diagnostic connector) to retrieve all stored codes and relevant freeze frame data. It is advisable to write down this information before clearing the codes, then test-drive the vehicle until the PCM either enters readiness mode or the code is reset.
If the PCM enters readiness mode at this time, the code is intermittent and may be more difficult to diagnose. In such cases, the conditions that led to the storage of the code may need to worsen before an accurate diagnosis can be made.
Step 2
If the code is immediately reset, the next step in your diagnosis will involve searching your vehicle information source for diagnostic flowcharts, connector pin-out charts, connector face views, and component testing procedures/specifications.
Step 3
Use the DVOM to test the voltage, ground, and signal at the transmission input and output speed sensors (key on and engine off). Input and output speed sensor circuits typically consist of a reference voltage, a signal wire, and a ground.
Step 4
Use the oscilloscope (connected to the signal circuit and ground) to check for spikes and glitches in the CPPS signal range.
