P0816 Downshift Switching Circuit

What Does It Mean?

This diagnostic trouble code (DTC) is a generic powertrain code and applies to many OBD-II vehicles (1996-newer). This may include, but is not limited to, vehicles from Ford, Acura, Vauxhall, Aston-Martin, Mercedes-Benz, Sprinter, etc. Although generic, the exact repair steps may vary depending on the year, make, model, and powertrain configuration.

If your vehicle has stored a P0816 code, it means that the Powertrain Control Module (PCM) has detected a malfunction in the downshift switch circuit. This type of code is typically limited to vehicles equipped with paddle shifters.

The Transmission Control Module (TCM) may be a standalone module or part of the PCM. The downshift shift buttons (paddles) are usually located on the steering wheel horn pad near the driver’s finger position. They are used as a type of sport shifter, typically in high-performance models. The PCM monitors the transmission gear selection against the input signals from the downshift switch to ensure continuity. Additionally, the PCM monitors the voltage of the downshift switch circuit to ensure it falls within established parameters.

If the PCM detects that the transmission gear selection does not match the gear selection signal input from the downshift switch, or if the switching circuit voltage is not within the allowed parameters, a P0816 code may be stored and a Malfunction Indicator Lamp (MIL) illuminated. Several ignition cycles (with a failure) may be required for the MIL to light up.

How Severe Is This DTC?

A stored P0816 code indicates that a serious electrical issue or a type of mechanical failure has occurred. In any case, the conditions that contributed to the storage of a code of this nature should be rectified as soon as possible.
What Are Some of the Symptoms of the Code?

Symptoms of a P0816 fault code may include:

    Manual downshift function (paddle) disabled
    Gear shift indicator reflects an incorrect gear
    No symptoms may appear

What Are Some Common Causes of the Code?

Causes

of this code may include:

    Faulty downshift switch
    Short or open circuits in the downshift switch circuit
    Faulty PCM or programming error

What Are the P0816 Troubleshooting Steps?

A diagnostic scanner, a digital volt/ohmmeter (DVOM), and a source of vehicle-specific diagnostic information will be needed to diagnose a P0816 code.

You can use your vehicle information source to locate a Technical Service Bulletin (TSB) that matches the vehicle’s year, make, and model; as well as engine size, stored codes, and presented symptoms. If you find one, it may provide useful diagnostic information.

Use the scanner (connected to the vehicle’s diagnostic connector) to retrieve all stored codes and relevant freeze frame data. It is a good idea to record this information before clearing the codes, then test the vehicle until the PCM enters readiness mode or the code resets.

If the PCM enters readiness mode at that point, the code is intermittent and may be much harder to diagnose. If this is the case, the conditions that contributed to the code storage may need to worsen before an accurate diagnosis can be made.

If the code immediately resets, the next step in your diagnosis will require you to consult your vehicle information source for diagnostic flowcharts, connector pinout diagrams, connector face views, and component testing procedures/specifications.

Step 1

Use the DVOM to test the voltage, ground, and signal output at the appropriate downshift switch. Typical downshift switching circuits consist of battery voltage (when activated) or ground (when deactivated).

Step 2

If the system circuits are functional, use the DVOM to test the downshift switching circuits to the PCM or transmission. Disconnect all controllers before using the DVOM for testing.

Step 3

Use your vehicle diagnostic information source and the DVOM to test the downshift switches as needed. Replace switches that do not test within system specifications.

Downshift switching codes are most often attributed to a switch failure

P0817 Starter Disable Circuit

What does it mean?

This diagnostic trouble code (DTC) is a generic powertrain code and applies to many OBD-II vehicles (1996-newer). This may include, but is not limited to, vehicles from Subaru, BMW, Mazda, Volkswagen, Audi, etc. Although generic, the exact repair steps may vary depending on the year, make, model, and powertrain configuration.

If your vehicle has stored a P0817 code, it means that the Powertrain Control Module (PCM) has detected a malfunction in the starter disable switch circuit. This type of code can be applicable to vehicles with manual or automatic transmissions.

The starter disable switch is typically a single-circuit open/closed switch that interrupts voltage between the ignition switch and the starter solenoid if the clutch is not depressed, the (manual) transmission is not in neutral, or the (automatic) transmission is not in park. Vehicle applications with an automatic transmission may have the starter disable switch integrated into the neutral safety switch or the gear selector. The Transmission Control Module (TCM) or the PCM monitors the starter disable circuit voltage with the ignition in the ON position. The TCM can be a standalone module or part of the PCM.

If the PCM detects that the voltage in the starter disable switch circuit is not within the allowed parameters, a P0817 code may be stored and a Malfunction Indicator Lamp (MIL) illuminated. Several ignition cycles (with a failure) may be required for the MIL to illuminate.

How severe is this DTC?

A stored P0817 code may be accompanied by a no-start condition and also indicates that an electrical issue or mechanical failure has occurred. The conditions that contributed to the storage of a code of this nature should be rectified as soon as possible.
What are some of the symptoms of the code?

Symptoms of a P0817 fault code may include:

Engine does not crank
Engine cranks with transmission in gear
No symptoms may be present

What are some of the common causes of the code?

Causes

of this code may include:

Faulty starter disable switch
Shorted or open wiring or connectors in the starter disable switch circuit
Faulty PCM or programming error

What are the troubleshooting steps for P0817?

A diagnostic scanner, a digital volt/ohmmeter (DVOM), and a source of vehicle-specific diagnostic information will be necessary to diagnose a P0817 code.

Use the scanner (connected to the vehicle’s diagnostic connector) to retrieve all stored codes and relevant freeze frame data. It is a good idea to record this information before clearing the codes, then test drive the vehicle until the PCM enters readiness mode or the code resets.

If the PCM enters readiness mode at that point, the code is intermittent and may be much more difficult to diagnose. If this is the case, the conditions that contributed to the code being stored may need to worsen before an accurate diagnosis can be made.

If the code resets immediately, the next step in your diagnosis will require you to consult your vehicle information source for diagnostic flowcharts, connector pinout diagrams, connector face views, and component testing procedures/specifications.
Step 1

Use the DVOM to test the voltage, ground, and signal output at the appropriate starter disable switch. Typical starter disable switch circuits consist of battery voltage (when activated) or ground (when deactivated).
Step 2

Use your vehicle diagnostic information source and the DVOM to test the starter disable switches, if necessary. Replace switches that do not test within system parameters.
Step 3

If the system switches and circuits are functional, use the DVOM to test the starter disable switch circuits to the starter, as well as to the PCM. Disconnect all controllers before using the DVOM for testing.

Starter disable switch circuit codes are most often attributed to a switch failure
Vehicles with manual transmissions often use multiple starter disable switches (one for the clutch and another for neutral)

Transmission Shift Disconnect Switch Input Circuit

What Does It Mean?

This diagnostic trouble code (DTC) is a generic powertrain code and applies to many OBD-II vehicles (1996-newer). This may include, but is not limited to, vehicles from Toyota, Land Rover, Volvo, BMW, Mini, Jaguar, etc. Although generic, the exact repair steps may vary depending on the year, make, model, and powertrain configuration.

If your vehicle has stored a P0818 code, it means that the powertrain control module (PCM) has detected a malfunction in the transfer case neutral safety switch circuit (also known as the shift selector switch). This type of code applies only to vehicles equipped with AWD/4WD automatic transmissions.

The transfer case neutral safety switch input circuit is typically integrated into the neutral safety switch or the shift selector. When the transfer case is placed in neutral (drivetrain disconnected), a voltage signal is input to the transmission control module (TCM) or the PCM. The controller also monitors the voltage of the transfer case neutral safety switch circuit whenever the ignition is in the ON position. The TCM may be a standalone module or part of the PCM.

If the PCM does not detect an appropriate voltage level on the transfer case neutral safety switch circuit, with the transfer case apparently in gear or neutral, a P0818 code may be stored and a malfunction indicator lamp (MIL) illuminated. Multiple ignition cycles (with a failure) may be required for the MIL to light up.

How Severe Is This DTC?

A stored P0818 code may be accompanied by a no-start condition and also indicates that an electrical issue or a serious mechanical failure has occurred. The conditions that contributed to storing a code of this nature should be rectified as soon as possible.
What Are Some of the Symptoms of the Code?

Symptoms of a P0818 fault code may include:

Engine does not start
Front axle does not engage or disengage
Engine starts with the transmission in gear
No symptoms may be present

What Are Some Common Causes of the Code?

Causes

of this code may include:

Faulty neutral safety switch or shift selector
Shorted or open wiring or connectors in the transfer case neutral safety switch input circuit
Faulty PCM or programming error

What Are the P0818 Troubleshooting Steps?

A diagnostic scanner, a digital volt/ohmmeter (DVOM), and a source of vehicle-specific diagnostic information will be needed to diagnose a P0818 code.

You can use your vehicle information source to locate a technical service bulletin (TSB) that matches the vehicle’s year, make, and model; as well as engine size, stored codes, and presented symptoms. If you find one, it may provide useful diagnostic information.

If the PCM enters readiness mode at that point, the code is intermittent and may be much more difficult to diagnose. If this is the case, the conditions that contributed to storing the code may need to worsen before an accurate diagnosis can be made.

If the code is immediately reset, the next step in your diagnosis will require you to consult your vehicle information source for diagnostic flowcharts, connector pinout diagrams, connector face views, and component testing procedures/specifications.
Step 1

Use the DVOM to test the voltage input of the transfer case neutral safety switch with the gear lever in different positions. Typical transfer case neutral safety switch input circuits consist of either battery voltage (when activated) or ground (when deactivated).
Step 2

Use your vehicle diagnostic information source and the DVOM to test the neutral safety/shift selector switches, if necessary. Replace switches that do not test within system parameters.
Step 3

If the system switches and circuits are functional, use the DVOM to test the transfer case neutral safety switch input circuits to the PCM. Disconnect all controllers before using the DVOM for testing.

Transfer case neutral safety switch input codes are most often attributed to a failure of the neutral safety switch

P0819 High and Low Shift Switch for Transmission Range Correlation

What Does It Mean?

This diagnostic code (DTC) is a generic powertrain code and applies to many OBD-II vehicles (1996-newer). This may include, but is not limited to, vehicles from VW, Audi, Honda, Ford, Kia, Lincoln, Hyundai, etc. Although generic, the exact repair steps may vary depending on the year, make, model, and powertrain configuration.

If your vehicle has stored a P0819 code, it means that the Powertrain Control Module (PCM) has detected a malfunction between the up/down shift switch and the transmission range switch (gear shift range). This type of code is typically limited to vehicles with automatic transmissions and paddle or sport shifters.

The Transmission Control Module (TCM) may be a standalone module or part of the PCM. The up/down shift (paddle) buttons are usually located on the steering wheel horn pad near the driver’s finger positions. They are used as a type of sport shifter, typically in high-performance models. The PCM monitors the transmission range switch to ensure that the gear selection is consistent with the input signals from the up/down shift switch. Additionally, the PCM monitors the up/down shift switch and the transmission range circuit voltage to ensure both are within established parameters.

If the PCM detects that the transmission gear selection is not consistent with the gear selection signal entered by the up/down shift switch or if the circuit voltage is not within the allowed parameters, a P0819 code may be stored and a Malfunction Indicator Lamp (MIL) illuminated. Several ignition cycles (with a failure) may be required for the MIL to light up.

How Severe Is This DTC?

A stored P0819 code indicates that a serious electrical issue or a type of mechanical failure has occurred. In any case, the conditions that contributed to the storage of a code of this nature should be rectified as soon as possible.
What Are Some of the Symptoms of the Code?

Symptoms of a P0819 fault code may include:

Manual up/down shift function (paddle) disabled
The gear shift indicator reflects an incorrect gear
No symptoms may appear

What Are Some Common Causes of the Code?

Causes

of this code may include:

Faulty up/down shift switch
Bad transmission range (shift) sensor
Short-circuited or open circuits in the up/down shift switch or transmission range circuit
Faulty PCM or programming error

What Are the Troubleshooting Steps for P0819?

A diagnostic scanner, a digital volt/ohmmeter (DVOM), and a source of vehicle-specific diagnostic information will be needed to diagnose a P0819 code.

Use the scanner (connected to the vehicle’s diagnostic connector) to retrieve all stored codes and relevant freeze frame data. It is a good idea to note this information before clearing the codes, then test the vehicle until the PCM enters readiness mode or the code resets.

Use the DVOM to test the voltage, ground, and signal output at the appropriate up/down shift and transmission range switches. Typical up/down shift circuits consist of battery voltage (when activated) or ground (when deactivated).
Step 2

Use your vehicle diagnostic information source and the DVOM to test the up/down shift and transmission range switches as needed. Replace switches that do not test within system specifications.
Step 3

If the system circuits are functional, use the DVOM to test the up/down shift switch and transmission range switch circuits to the PCM or transmission. Disconnect all controllers before using the DVOM for testing.

Up/down shift correlation codes to transmission range are most often attributed to a switch failure

P081A Low Starter Disable Circuit

What Does It Mean?

If your vehicle has stored a P081A code, it means that the Powertrain Control Module (PCM) has detected a higher than expected voltage level in the starter disable switch circuit. This type of code can be applicable to both manual and automatic transmission vehicles.

The starter disable switch is typically a single-circuit open/closed switch that interrupts voltage between the ignition switch and the starter solenoid if the clutch is not depressed, the (manual) transmission is not in neutral, or the (automatic) transmission is not in park. Vehicle applications with an automatic transmission may have the starter disable switch integrated into the neutral safety switch or the gear selector. The Transmission Control Module (TCM) or the PCM starter monitor deactivates the circuit voltage with the ignition in the ON position. The TCM can be a standalone module or part of the PCM.

If the PCM detects that the voltage in the starter disable switch circuit is not within the allowed parameters, a P081A code may be stored and a Malfunction Indicator Lamp (MIL) illuminated. Multiple ignition cycles (with a failure) may be required for the MIL to illuminate.

How Severe Is This DTC?

A stored P081A code may be accompanied by a no-start condition and also indicates that an electrical issue or mechanical failure has occurred. The conditions that contributed to the storage of a code of this nature should be rectified as soon as possible.
What Are Some of the Symptoms of the Code?

Symptoms of a P081A fault code may include:

Engine does not crank
Engine cranks with transmission in gear
No symptoms may be present

What Are Some of the Common Causes of the Code?

Causes

of this code may include:

Faulty starter disable switch
Shorted or open wiring or connectors in the starter disable switch circuit
Faulty PCM or programming error

What Are the P081A Troubleshooting Steps?

A diagnostic scanner, a digital volt/ohmmeter (DVOM), and a source of vehicle-specific diagnostic information will be needed to diagnose a P081A code.

You can use your vehicle information source to locate a Technical Service Bulletin (TSB) that matches the vehicle’s year, make, and model; as well as the engine size, stored codes, and presented symptoms. If you find one, it might provide helpful diagnostic information.

Use the scanner (connected to the vehicle’s diagnostic connector) to retrieve all stored codes and relevant freeze frame data. It is a good idea to record this information before clearing the codes, then test drive the vehicle until the PCM enters readiness mode or the code resets.

If the code immediately resets, the next step in your diagnosis will require you to search your vehicle information source for diagnostic flowcharts, connector pinout diagrams, connector face views, and component testing procedures/specifications.
Step 1

Use your vehicle diagnostic information source and the DVOM to test the starter disable switches, if necessary. Replace any switches that do not test within system parameters.
Step 3

Starter disable switch circuit codes are most often attributed to a switch failure
Manual transmission vehicles often use multiple starter disable switches (one for the clutch and another for neutral)

P081B Starter Disable Circuit High

What does it mean?

If your vehicle has stored a P081B code, it means that the Powertrain Control Module (PCM) has detected a voltage level lower than expected in the starter disable switch circuit. This type of code can be applicable to both manual and automatic transmission vehicles.

The starter disable switch is typically a single-circuit open/closed switch that interrupts the voltage between the ignition switch and the starter solenoid if the clutch is not depressed, the (manual) transmission is not in neutral, or the (automatic) transmission is not in park. Vehicle applications with an automatic transmission may have the starter disable switch integrated into the neutral safety switch or gear selector. The Transmission Control Module (TCM) or the PCM’s starter monitor deactivates the circuit voltage with the ignition in the ON position. The TCM can be a standalone module or part of the PCM.

If the PCM detects that the voltage in the starter disable switch circuit is not within the allowed parameters, a P081B code may be stored and a Malfunction Indicator Lamp (MIL) illuminated. Several ignition cycles (with a failure) may be required for the MIL to illuminate.

P081B
How severe is this DTC?

A stored P081B code may be accompanied by a no-start condition and also indicates that an electrical issue or mechanical failure has occurred. The conditions that contributed to the storage of a code of this nature should be rectified as soon as possible.
What are some of the symptoms of the code?

Symptoms of a P081B fault code may include:

Engine does not crank
Engine cranks with transmission in gear
No symptoms may be present

What are some of the common causes of the code?

Causes

of this code may include:

Faulty starter disable switch
Shorted or open wiring or connectors in the starter disable switch circuit
Faulty PCM or programming error

What are the troubleshooting steps for P081B?

A diagnostic scanner, a digital volt/ohmmeter (DVOM), and a source of vehicle-specific diagnostic information will be needed to diagnose a P081B code.

Use the scanner (connected to the vehicle’s diagnostic connector) to retrieve all stored codes and relevant freeze frame data. It is a good idea to record this information before clearing the codes, then test drive the vehicle until the PCM enters readiness mode or the code resets.

Use your vehicle diagnostic information source and the DVOM to test the starter disable switches, if necessary. Replace switches that do not test within system parameters.
Step 3

P081C Park Position Input Signal – Circuit Malfunction

What Does This Code Mean?

Diagnostic Trouble Code (DTC) P081C is a generic powertrain code applicable to OBD-II vehicles (1996 and newer). It may affect multiple brands, including Land Rover, Volvo, BMW, Mini, Jaguar, among others. Although this code is generic, repair procedures can vary depending on the year, make, model, and powertrain configuration.

A P081C code means that the Powertrain Control Module (PCM) has detected a malfunction in the PARK input circuit of the neutral safety switch (also called the gear selector). This code applies only to vehicles equipped with automatic transmissions.

The PARK input circuit is typically integrated into the neutral safety switch or the gear selector. When the transmission is in the PARK position, a voltage signal is sent to the Transmission Control Module (TCM) or the PCM. The latter also monitors the circuit voltage whenever the ignition is turned on. The TCM can be a separate module or integrated into the PCM.

If the PCM does not detect the correct voltage when the transmission is supposed to be in PARK or neutral, it stores a P081C code and illuminates the Malfunction Indicator Lamp (MIL). Note that multiple ignition cycles may be required before the MIL illuminates.

Severity of Code P081C

This code is considered serious. It can cause a no-start condition and indicates an electrical or mechanical fault that should be addressed promptly.

Possible Symptoms

Symptoms associated with a P081C code may include:

Engine does not start
Engine starts while the transmission is engaged
No apparent symptoms in some cases

Possible Causes

The most common causes of a P081C code are:

Faulty neutral safety switch or gear selector
Short circuit or open in the wiring or connectors of the PARK input circuit
PCM fault or programming error

Diagnostic and Repair Steps

To diagnose a P081C code, you will need:

A diagnostic tool (OBD-II scanner)
A digital voltmeter/ohmmeter (DVOM)
Vehicle-specific technical documentation

1. Checking Technical Service Bulletins (TSBs)
Consult TSBs for your vehicle (year, model, engine). They may contain known fixes for this issue.

2. Reading Codes and Freeze Frame Data
Using the scanner, retrieve all stored codes and freeze frame data. Record this information before clearing the codes.
Then test drive the vehicle. If the PCM enters ready mode without the code returning, the problem is intermittent. If the code resets quickly, continue diagnostics.

3. Testing the PARK Input Circuit

Use the DVOM to test voltage on the PARK input circuit of the neutral position switch or gear selector.
Normally, this circuit should display either battery voltage (when activated) or ground (when deactivated).

4. Testing the Neutral Safety Switch / Gear Selector

Test the switch with the DVOM according to manufacturer specifications.
Replace any switch that does not meet specified tolerances.

5. Checking Circuits to the PCM

If switches and circuits appear to be functioning correctly, test the circuits leading to the PCM.
Disconnect modules before performing these tests to avoid damaging electronic components.

Important Note:
In most cases, a P081C code is caused by a faulty neutral safety switch.

Neutral Input Circuit

What Does It Mean?

This diagnostic trouble code (DTC) is a generic powertrain code and applies to many OBD-II vehicles (1996-newer). This may include, but is not limited to, Land Rover, Volvo, BMW, Mini, Jaguar vehicles, etc. Although generic, the exact repair steps may vary depending on the year, make, model, and powertrain configuration.

If your vehicle has stored a P081D code, it means that the Powertrain Control Module (PCM) has detected a malfunction in the NEUTRAL input circuit of the neutral safety switch (also called the gear selector switch). This type of code applies only to vehicles with automatic transmissions.

The NEUTRAL input circuit is typically integrated into the neutral safety switch or gear selector. When the transmission is placed in NEUTRAL, a voltage signal is input to the Transmission Control Module (TCM) or PCM. The controller also monitors the circuit voltage whenever the ignition is in the ON position. The TCM may be a standalone module or part of the PCM.

If the PCM does not detect an appropriate voltage level on the NEUTRAL circuit, with the transmission apparently in Park or Neutral, a P081D code may be stored and a Malfunction Indicator Lamp (MIL) illuminated. Multiple ignition cycles (with a fault) may be required for the MIL to illuminate.

How Severe Is This DTC?

A stored P081D code may be accompanied by a no-start condition and also indicates that an electrical issue or mechanical failure has occurred. Conditions that contributed to storing a code of this nature should be rectified as soon as possible.
What Are Some of the Symptoms of the Code?

Symptoms of a P081D trouble code may include:

Engine does not start
Engine starts with transmission in gear
No symptoms may be present

What Are Some Common Causes of the Code?

Causes

of this code may include:

Faulty neutral safety switch or gear selector
Shorted or open wiring or connectors in the NEUTRAL input circuit
Faulty PCM or programming error

What Are the P081D Troubleshooting Steps?

A diagnostic scanner, a digital volt/ohmmeter (DVOM), and a source of vehicle-specific diagnostic information will be needed to diagnose a P081D code.

Use the scanner (connected to the vehicle’s diagnostic connector) to retrieve all stored codes and relevant freeze frame data. It’s a good idea to record this information before clearing the codes, then test-drive the vehicle until the PCM enters readiness mode or the code resets.

If the PCM enters readiness mode at that point, the code is intermittent and may be much harder to diagnose. If this is the case, the conditions that contributed to storing the code may need to worsen before an accurate diagnosis can be made.

Use the DVOM to test the NEUTRAL input voltage at the appropriate neutral position/shift selector. Typical NEUTRAL input circuits consist of battery voltage (when activated) or ground (when deactivated).
Step 2

Use your vehicle diagnostic information source and the DVOM to test the neutral safety/shift selector switches, if necessary. Replace switches that do not test within system parameters.
Step 3

If the system switches and circuits are functional, use the DVOM to test the PCM’s NEUTRAL input circuits. Disconnect all controllers before using the DVOM for testing.

NEUTRAL input codes are most often attributed to a neutral safety switch failure

P081E Excessive Clutch Slip B

What Does It Mean?

This diagnostic trouble code (DTC) is a generic powertrain code and applies to many OBD-II vehicles (1996-newer). This may include, but is not limited to, vehicles from Volkswagen, Porsche, Honda, Audi, Acura, etc. Although generic, the exact repair steps may vary depending on the year, make, model, and powertrain configuration.

If your vehicle has stored a P081E code, it means that the Powertrain Control Module (PCM) has received an input data signal from the input and output speed sensors indicating that the clutch is slipping excessively. The B designation clutch indicates that the vehicle is equipped with a Clutch Pedal Position Sensor (CPPS) that operates similarly to a Throttle Position Sensor (TPS).

The Transmission Control Module (TCM) may be a standalone unit but is most often integrated into a single housing with the Engine Control Module (ECM). This is referred to as the PCM.

The PCM uses input signals from various engine and transmission sensors to calculate the maximum allowable transmission (clutch) slip degree. Wear on the clutch disc and pressure plate, as well as mechanical failure, can lead to excessive clutch slippage. CPPS voltage deviations can also cause a P081E to be stored. The PCM uses voltage input signals from the transmission input speed sensor and transmission output speed sensor, along with the clutch pedal position, to determine if the clutch is operating within the parameters for maximum allowable slip.

Often, when the friction material on the clutch disc wears below a certain level, the clutch begins to slip. This condition is typically accompanied by the distinct smell of burnt friction material.

If the PCM detects a degree of transmission (clutch) slip that exceeds the maximum allowable parameters, a P081E code may be stored and a Malfunction Indicator Lamp (MIL) illuminated. Several ignition cycles (with a failure) may be required for the MIL to light up.

How Severe Is This DTC?

A stored P081E code indicates that a serious electrical issue or clutch failure has occurred. In any case, the conditions that contributed to the storage of a code of this nature should be rectified as soon as possible.
What Are Some of the Symptoms of the Code?

Symptoms of a P081E trouble code may include:

Transmission slipping
Hard gear engagement
Clutch engagement occurs near the top
Strong smell of burnt friction material

What Are Some of the Common Causes of the Code?

Causes

of this code may include:

Faulty CPPS sensor
Worn clutch disc and/or pressure plate
Defective input or output speed sensor
Shorted wiring for input/output speed sensors
Faulty PCM or programming error

What Are the P081E Troubleshooting Steps?

Before attempting to diagnose a P081E, ensure that the clutch, pressure plate, and release bearing are functioning correctly. You will also want to check the clutch arms and linkages, as well as the clutch hydraulic system, if applicable.

A diagnostic scanner, a digital volt/ohmmeter (DVOM), and a source of vehicle-specific diagnostic information will be necessary to diagnose a P081E code. An oscilloscope may also be helpful when attempting to diagnose input and output speed sensor malfunctions. The CPPS output voltage can also be monitored using the DVOM or oscilloscope. The latter is more effective for detecting voltage spikes and glitches.

With the clutch functioning properly, proceed to the first step of diagnosis.

Step 1

Use the scanner (connected to the vehicle’s diagnostic connector) to retrieve all stored codes and relevant freeze frame data. It is a good idea to note this information before clearing the codes, then test-drive the vehicle until the PCM enters readiness mode or the code resets.

If the PCM enters readiness mode at this point, the code is intermittent and may be much more difficult to diagnose. If this is the case, the conditions that contributed to the code being stored may need to worsen before an accurate diagnosis can be made.
Step 2

Use the DVOM to test the voltage, ground, and signal at the transmission input and output speed sensors (key on, engine off). The 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.

Most B clutch slip codes can be attributed to a CPPS failure

P0820 Shift Lever X-Y Position Sensor Circuit

P0820 X-Y Shift Lever Position Sensor Circuit

Possible Causes

List of components that can trigger the appearance of this code

Wiring harness
Connector poor contact
Shift lever position sensor
Engine control module/transmission control module