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DTC codes / P09xx · Transmission / P0955

P0955Auto Shift Manual Mode Circuit

P0955 indicates that the transmission control module (TCM) has detected an electrical fault in the circuit for the Auto Shift Manual Mode feature, which allows the driver to select gears manually in an automatic transmission. The computer monitors voltage or current on the circuit and sets the code when the signal is outside the expected range, often due to a wiring issue or a failed switch.

SystemPowertrain
Code typeGeneric (all makes)
SeverityMedium
Fix difficultyIntermediate
AreaTransmission

Symptoms you may notice

  • The manual shift mode may not engage when selected, leaving the transmission in automatic mode
  • The gear indicator on the instrument cluster may flash or show an incorrect gear
  • The transmission may default to a limp mode, limiting gear selection
  • The manual mode button or shift lever may feel unresponsive
  • Often no symptoms besides the warning light, especially if the fault is intermittent

Common causes, most likely first

  1. Faulty manual mode switch or selector lever assembly
  2. Damaged wiring or connector at the transmission range sensor or manual shift circuit
  3. Corroded or loose electrical connections at the TCM
  4. Failed transmission range sensor (also called neutral safety switch)
  5. Internal TCM fault, though less common
  6. Aftermarket accessories or poor previous repairs interfering with the circuit

How to diagnose and fix it

  1. Verify the code with a scan tool and check for related codes in the TCM
  2. Inspect the manual mode switch and wiring for visible damage or corrosion
  3. Test the switch operation with a multimeter and compare to manufacturer specifications
  4. Check the transmission range sensor for proper alignment and continuity
  5. Inspect and clean TCM connectors and grounds
  6. Repair or replace faulty wiring or connectors as needed
  7. If all else fails, consult a professional for TCM diagnostics or replacement

Before you replace the manual mode switch

  • A loose or corroded connector at the transmission range sensor often mimics a failed manual mode switch, so always inspect connections first.
  • The code can be set by a low battery or charging system issue that causes voltage spikes, so check battery health before condemning components.
  • On some vehicles, the manual mode circuit is integrated into the shift lever assembly, and a simple adjustment of the cable can resolve the fault.
  • Intermittent faults may only appear when the transmission is hot or after driving over rough roads, so wiggle-test wiring while monitoring live data.
  • Replacing the TCM without checking the circuit is a costly mistake; the fault is usually in the wiring or switch.

Can I keep driving with P0955?

You can usually continue driving if the transmission still shifts automatically, but avoid using the manual mode until repaired. If the transmission enters limp mode or shifts erratically, seek professional diagnosis promptly.

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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