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DTC codes / P09xx · Transmission / P0918

P0918Gear Shift Position Circuit Intermittent

P0918 indicates that the transmission control module (TCM) or powertrain control module (PCM) has detected an intermittent fault in the gear shift position circuit, which reports the current gear or selector lever position. The circuit signal momentarily drops out or becomes erratic, so the computer cannot reliably determine the gear position, even though the fault may not be present at the moment of diagnosis.

SystemPowertrain
Code typeGeneric (all makes)
SeverityMedium
Fix difficultyIntermediate
AreaTransmission

Symptoms you may notice

  • Illumination of the check engine light or transmission warning light, often with no other noticeable symptoms
  • Harsh or delayed gear shifts as the transmission control module defaults to a limp-home mode
  • Transmission may stick in a single gear or fail to engage certain gears
  • Erratic or flickering gear position indicator on the instrument cluster
  • Intermittent loss of power or unexpected downshifts while driving
  • In some cases, the vehicle may enter limp mode and limit engine speed

Common causes, most likely first

  1. Worn or damaged wiring harness between the transmission range sensor and the TCM/PCM, often due to chafing or heat exposure
  2. Corroded, loose, or contaminated electrical connector at the transmission range sensor or at the TCM/PCM
  3. Faulty transmission range sensor (also called gear position sensor or neutral safety switch) with internal intermittent contact
  4. Poor ground connection for the TCM/PCM or for the transmission range sensor circuit
  5. Internal fault in the TCM/PCM affecting the signal processing circuit
  6. Aftermarket electrical accessories or poor previous repairs introducing interference or resistance in the circuit

How to diagnose and fix it

  1. Connect a scan tool and retrieve all stored and pending codes, then clear codes and test-drive to see if P0918 returns; note any freeze-frame data to identify conditions when the fault occurred.
  2. Visually inspect the transmission range sensor and its connector for corrosion, loose pins, or damaged wiring; repair or replace connector terminals as needed.
  3. Perform a wiggle test on the wiring harness while monitoring the gear position parameter on the scan tool to reproduce the intermittent fault and locate the damaged section.
  4. Check the sensor's resistance or voltage output through its full range of motion according to the manufacturer's specification; replace the sensor if readings are erratic or out of spec.
  5. Verify the integrity of the ground circuit for the TCM/PCM and the sensor, cleaning and tightening grounds as necessary.
  6. If the circuit and sensor test good, check for technical service bulletins (TSBs) or software updates for the TCM/PCM that address intermittent gear position signals.
  7. As a last step, substitute a known-good TCM/PCM only after all wiring and sensor tests pass, since intermittent internal faults are rare but possible.

Intermittent Gear Position Circuit Traps

  • A common oversight is replacing the transmission range sensor without first checking the connector pins for fretting corrosion, which can cause intermittent signals even when the sensor itself is good.
  • The code may set only under specific conditions such as cold starts, high vibration, or after driving over rough roads, so a simple static test often misses the fault.
  • Aftermarket remote starters or alarm systems tapped into the gear position wiring can introduce resistance or interference that mimics a failing sensor.
  • On some vehicles, a weak battery or charging system fluctuation can cause the TCM to log intermittent circuit codes without any actual wiring fault.
  • The gear shift position circuit may share a reference voltage or ground with other sensors, so a fault in a related circuit can trigger P0918 as a secondary code.

Can I keep driving with P0918?

The vehicle is generally safe to drive short distances to a repair shop, but avoid sustained highway speeds or heavy loads because the transmission may enter limp mode without warning. If the transmission exhibits harsh shifting or fails to engage gears, stop driving and seek professional diagnosis immediately.

Tools that help

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Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.

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