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DTC codes / Volkswagen codes / P1793

P1793 · VolkswagenOutput Speed Sensor 2 Circuit No Signal

P1793 on Volkswagen vehicles means the transmission control module (TCM) is not receiving a usable signal from the second output speed sensor, which monitors the rotational speed of the transmission output shaft. The TCM compares this signal against engine speed and the other speed sensors to manage shift timing and torque converter lockup, so a missing signal triggers the code and often forces a limp-home strategy.

SystemPowertrain
Code typeVolkswagen specific
SeverityMedium
Fix difficultyIntermediate
AreaTransmission

Symptoms you may notice

  • Illumination of the transmission warning light or check engine light, often with no other noticeable symptoms at first
  • Harsh or delayed gear engagements, especially when selecting drive or reverse from a stop
  • Erratic or missing shift points, with the transmission holding a gear longer than normal or refusing to upshift
  • Transmission stuck in a limp-home or fail-safe mode that limits vehicle speed and gear selection
  • Speedometer fluctuation or failure if the instrument cluster derives vehicle speed from the same output speed signal
  • Torque converter clutch failing to engage or engaging abruptly, causing shudder or poor fuel economy

Common causes, most likely first

  1. Faulty output speed sensor 2 itself, either an internal open circuit or a failed hall-effect element
  2. Damaged or corroded wiring harness between the sensor and the transmission control module, including chafed insulation or broken strands
  3. Loose, corroded, or backed-out pins at the sensor connector or the TCM connector
  4. Metal debris or sludge buildup on the sensor tip, preventing it from reading the reluctor wheel teeth
  5. Damaged or missing teeth on the output shaft reluctor wheel, or excessive end play in the output shaft
  6. Internal transmission mechanical wear that alters the air gap between the sensor and the reluctor wheel
  7. Failed transmission control module driver circuit for the sensor, though this is less common than wiring or sensor faults

How to diagnose and fix it

  1. Scan all modules for stored and pending codes, then verify live output speed 2 data in the TCM while driving to confirm the signal is missing or intermittent
  2. Visually inspect the sensor connector and harness for corrosion, chafing, or loose pins, and check the sensor mounting bolt for tightness
  3. Remove the sensor and inspect the tip for metal shavings or sludge, and check the reluctor wheel through the sensor hole for damaged teeth
  4. Measure the sensor resistance and compare it to the manufacturer specification, then check for continuity and short-to-ground on each wire from the sensor connector to the TCM
  5. Back-probe the sensor signal wire with a scope or graphing multimeter while rotating the output shaft to confirm a clean square wave or sine wave pattern
  6. If wiring and sensor test good, substitute a known-good sensor and clear the code to see whether the fault returns
  7. If the code persists after sensor and wiring repairs, check TCM software updates and inspect the TCM connector and internal driver circuit before condemning the module

What the output speed sensor 2 really does

  • Many Volkswagen transmissions use two output speed sensors, and a failed sensor 2 can set P1793 while sensor 1 still provides enough data for the speedometer, so the driver may see no gauge symptoms at all.
  • A common misdiagnosis is replacing the sensor when the real fault is a chafed harness near the transmission mount or a corroded connector pin that only loses contact over bumps or when the engine bay is hot.
  • Metal paste on the sensor tip from normal clutch or gear wear can bridge the air gap and kill the signal without any visible damage to the sensor or reluctor wheel, so cleaning the tip often restores operation.
  • This code does not always mean the transmission is mechanically failing; a simple open circuit in the sensor wiring will set the same code and trigger the same limp-home behavior.
  • On some Volkswagen models the output speed sensor signal is shared with the ABS module for vehicle speed calculation, so a P1793 can appear alongside ABS or speedometer-related codes that lead technicians away from the transmission.

Can I keep driving with P1793?

You can usually drive the vehicle to a repair shop, but expect harsh shifts and a possible limp-home mode that limits speed, so avoid highway driving and heavy acceleration until the fault is repaired. Continuing to drive with the transmission in fail-safe mode for an extended period can increase wear on the clutch packs.

Tools that help

Tools we recommend are in the Auto Veteran shop on Amazon. As an Amazon Associate we earn from qualifying purchases.

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

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