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DTC codes / Volkswagen codes / P1446

P1446 · VolkswagenCatalyst Temperature Circuit Short To Ground

P1446 on Volkswagen vehicles means the engine control module (ECM) has detected a short to ground on the catalyst temperature sensor circuit, which is used to monitor the temperature of the catalytic converter on certain models. The ECM expects a specific voltage range from the sensor and sees a signal that is pulled too low, indicating a wiring fault rather than a normal temperature reading.

SystemPowertrain
Code typeVolkswagen specific
SeverityMedium
Fix difficultyIntermediate
AreaAuxiliary emission controls

Symptoms you may notice

  • Illumination of the check engine light (malfunction indicator lamp) on the dashboard.
  • Often no symptoms besides the warning light, especially if the fault is intermittent.
  • Possible slight decrease in fuel economy if the ECM enters a default operating strategy.
  • Rough running or hesitation in some cases if the ECM misinterprets catalyst temperature and adjusts fueling.
  • In rare instances, the engine may enter limp mode to protect the catalytic converter from overheating.
  • No noticeable change in vehicle performance for many drivers.

Common causes, most likely first

  1. Damaged or chafed wiring harness between the catalyst temperature sensor and the ECM, causing the signal wire to contact ground.
  2. Corroded or loose electrical connector at the catalyst temperature sensor or at the ECM.
  3. Internal short to ground within the catalyst temperature sensor itself.
  4. Moisture intrusion into the sensor connector or wiring, leading to a ground path.
  5. Faulty ECM (rare, but possible if the internal circuit for the sensor signal is shorted).
  6. Aftermarket or improperly installed accessories (e.g., alarm systems, audio equipment) that tap into the wiring harness and create a ground short.
  7. Physical damage to the sensor or wiring from road debris or exhaust work.

How to diagnose and fix it

  1. Visually inspect the catalyst temperature sensor wiring and connector for obvious damage, corrosion, or contact with ground; repair as needed.
  2. Disconnect the sensor and check for a short to ground on the signal wire using a digital multimeter (DMM) set to resistance or continuity; isolate the fault by wiggling the harness.
  3. Check the sensor's internal resistance or voltage output according to Volkswagen service information to rule out an internal short.
  4. Inspect the ECM connector for corrosion or loose pins, and check for a short to ground on the ECM side of the circuit.
  5. If the wiring and sensor check out, perform a continuity test from the sensor connector to the ECM to ensure the signal wire is not shorted to ground along its length.
  6. Replace the catalyst temperature sensor if it is found to be internally shorted, then clear the fault codes and verify the repair with a test drive.
  7. If the fault persists after all external checks, suspect a faulty ECM and perform further diagnostics before replacement.

Common misdiagnosis traps for P1446

  • A short to ground in the catalyst temperature circuit is often caused by a rubbed-through wire near the exhaust heat shield or where the harness passes through the body, not by a failed sensor.
  • Technicians sometimes replace the catalytic converter unnecessarily because they misread P1446 as a catalyst efficiency code; this code specifically points to the temperature sensor circuit, not the converter's performance.
  • Intermittent shorts can be temperature-dependent or vibration-related, so a wiggle test of the harness while monitoring live data is more effective than a static resistance check.
  • Aftermarket electrical accessories wired into the same circuit can introduce a ground short that only appears when the accessory is powered on.
  • The ECM may set P1446 along with other sensor codes if a common ground point is corroded, so always check ground connections in the engine bay.

Can I keep driving with P1446?

You can generally continue driving with P1446 because the fault is electrical and does not immediately affect engine operation, but avoid sustained high-speed or heavy-load driving until it is repaired. If the check engine light begins flashing or you notice performance changes, stop driving and seek professional diagnosis.

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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