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DTC codes / Mazda codes / P1772

P1772 · MazdaThrottle Position Sensor Circuit Shorted To Transmission Control Module

P1772 on Mazda vehicles indicates that the Transmission Control Module (TCM) has detected a short to ground or short to power in the Throttle Position Sensor (TPS) signal circuit. The TCM monitors the TPS voltage to coordinate shift points and line pressure, and when the signal is outside the expected range, it stores this code and may default to a limp-home mode.

SystemPowertrain
Code typeMazda specific
SeverityMedium
Fix difficultyProfessional
AreaTransmission

Symptoms you may notice

  • The check engine light or transmission warning light illuminates on the dashboard.
  • Harsh or delayed transmission shifts, often accompanied by a default to a single gear or limp mode.
  • The engine may idle erratically or hesitate during acceleration due to incorrect throttle input to the TCM.
  • Poor fuel economy or reduced engine power as the TCM limits operation to protect the transmission.
  • In some cases, no drivability symptoms are noticed besides the warning light, especially if the short is intermittent.

Common causes, most likely first

  1. Chafed or damaged wiring in the TPS signal circuit where it rubs against the transmission housing or other components.
  2. Corrosion or water intrusion in the TPS connector or TCM connector pins, causing a short.
  3. A failed Throttle Position Sensor internally shorted, sending an incorrect signal to the TCM.
  4. A faulty Transmission Control Module (TCM) with an internal short on the TPS input circuit.
  5. Aftermarket accessories or poor previous repairs that tapped into the TPS wiring and created a short.
  6. A short to power from a nearby circuit that shares the same loom, such as the reverse light or ignition wiring.

How to diagnose and fix it

  1. Perform a visual inspection of the TPS and TCM connectors for corrosion, loose pins, or water intrusion, and clean or repair as needed.
  2. Check the TPS signal voltage at the sensor with a multimeter and compare to the manufacturer's specification through the full throttle range.
  3. Disconnect the TCM and TPS connectors and measure resistance from the TPS signal wire to ground and to power to identify a short.
  4. Inspect the wiring harness along the intake manifold and transmission bell housing for chafing, melted insulation, or pinched sections.
  5. If the wiring and sensor test good, substitute a known-good TCM and retest to rule out an internal TCM fault.
  6. Clear the code and perform a road test with a scan tool to verify the TPS signal reads correctly and the code does not return.

What most technicians miss on P1772

  • A common oversight is replacing the TPS without checking the TCM connector for corrosion, which often causes the same short and leads to a repeat failure.
  • The TPS signal wire can short to the transmission range sensor wiring in the same loom, so inspect that section even though the code points to the TCM.
  • Intermittent P1772 codes often appear after engine washing or heavy rain, indicating water intrusion in a connector rather than a failed component.
  • A shorted TPS can also set throttle-related engine codes, so always check for companion codes that might confirm the root cause.
  • Some aftermarket alarm or remote start installations tap into the TPS wire and create a short that only appears when the accessory is active.

Can I keep driving with P1772?

If the transmission is in limp mode or shifting harshly, avoid highway driving and seek repair promptly to prevent transmission damage. If the only symptom is the warning light and the car drives normally, you can drive cautiously to a workshop, but avoid aggressive acceleration or towing.

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 Mazda vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.

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