What it means
The gear shift position circuit A reports a circuit intermittent fault. Gear shift position feedback is unreliable on this channel.
At a glance
- Usually lights the check-engine light
- The engine or gearbox may go into limp mode
How it works
Gear shift position circuit A tells the TCM where the shift mechanism is, and the module checks whether that feedback remains stable. P0918 sets when the circuit A signal drops out or becomes erratic intermittently, often as a connector or wire loses contact with vibration or movement.
Common causes
Most likely first.
- Position sensor failed
- Wiring fault
- Connector with intermittent contact under vibration
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
- Check stored and pending codes and freeze-frame data, then monitor circuit A live data to see when its position signal drops out.
- Inspect the circuit A sensor connector and harness for loose pins, corrosion, water intrusion, chafing, or strain near moving parts.
- With live data displayed, gently move the connector and harness to locate a vibration-sensitive interruption without pulling on the wires.
- Check circuit A power, ground, and signal continuity while moving the harness, following the wiring diagram.
- If the connection remains stable, test the position sensor for intermittent output while selecting gears, using the manufacturer's specification.
Common fixes
- Secure a loose circuit A connector and repair a wire that breaks contact when moved.
- Clean or replace corroded terminals and restore connector sealing.
- Repair chafed wiring and secure the harness away from moving or vibrating parts.
- Replace the circuit A position sensor if its output intermittently drops out with sound wiring.
Can I keep driving?
Avoid long trips if the fault causes unpredictable shifts, and stop if gear selection or drive engagement is lost. An intermittent position signal can abruptly trigger limp mode or disrupt a shift.
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.