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.
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 helpful diagnostic information.
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.
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 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