What it means
The Neutral input circuit has an electrical fault, so the controller may not receive a reliable Neutral signal.
At a glance
- Usually lights the check-engine light
How it works
The Neutral input tells the control module that the transmission or selector is in Neutral. The module monitors this electrical signal and sets P081D when the input circuit is faulty, so the reported Neutral state may not match the selector.
Common causes
Most likely first.
- Open circuit in Neutral input wiring
- Short to ground or power in the input circuit
- Loose or corroded connector
- Faulty Neutral switch or sensor
- Control module circuit fault
Symptoms
- Check engine or transmission warning light on
- Harsh, delayed, or missing shifts
- Possible limp mode (locked in one gear)
- Slipping or shuddering during gear changes
How to diagnose it
- Save freeze-frame data and scan related transmission codes to establish when the Neutral input fault was recorded.
- Watch the Neutral input and range data on a scan tool while moving the selector into and out of Neutral, checking whether the displayed state follows.
- Inspect the Neutral switch or sensor connector and wiring for looseness, corrosion, chafing, or backed-out pins.
- Test the Neutral input circuit for an open or short to ground or power using the wiring diagram and manufacturer's procedure.
- If the circuit is intact, test the Neutral switch or sensor and the control-module input as specified for the vehicle.
Common fixes
- Reconnect a loose Neutral input connector.
- Clean or replace corroded or damaged connector terminals.
- Repair open, chafed, or shorted Neutral input wiring.
- Replace a Neutral switch or sensor that fails its test.
- Repair or replace the control module only if its input circuit is confirmed faulty.
Can I keep driving?
The vehicle may not recognize Neutral correctly, which can interfere with starting or shifting depending on the design. Keep the parking brake applied and the vehicle secured when stationary, and do not assume it is in Neutral based only on the selector position.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.