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DTC codes / Mazda codes / P1746

P1746 · MazdaElectronic Pressure Control Solenoid Circuit Open

P1746 on Mazda vehicles means the transmission control module (TCM) has detected an open circuit in the electronic pressure control solenoid, which is the solenoid that regulates hydraulic line pressure inside the automatic transmission. The TCM commands a current through the solenoid and monitors the return voltage; when the circuit is broken, the feedback voltage falls outside the expected range and the code is stored.

SystemPowertrain
Code typeMazda specific
SeverityMedium
Fix difficultyIntermediate
AreaTransmission

Symptoms you may notice

  • Illumination of the check engine light or transmission warning light, often with no other symptoms
  • Harsh or delayed shifts, especially when engaging drive or reverse
  • Transmission stuck in a single gear (limp mode) with reduced performance
  • Slipping or flaring during gear changes under acceleration
  • Erratic line pressure causing shudder or clunking when shifting

Common causes, most likely first

  1. Broken or corroded wire in the electronic pressure control solenoid circuit
  2. Failed electronic pressure control solenoid (open internal coil)
  3. Damaged or disconnected electrical connector at the transmission
  4. Faulty transmission control module (TCM) driver circuit
  5. Internal transmission harness damage from heat or fluid contamination
  6. Poor ground connection for the solenoid circuit

How to diagnose and fix it

  1. Inspect the transmission wiring harness and connectors for obvious damage or corrosion
  2. Measure the resistance of the electronic pressure control solenoid at the transmission connector and compare to specification
  3. Check for continuity between the TCM connector and the solenoid connector to isolate an open wire
  4. Verify power and ground supplies to the solenoid circuit with the ignition on
  5. If the solenoid coil is open, replace the solenoid and perform a transmission fluid service
  6. If wiring is intact but the solenoid tests good, test the TCM output driver or substitute a known-good TCM
  7. Clear the code and perform a relearn or adaptation drive cycle to confirm the repair

What P1746 Misdiagnosis Often Misses

  • A loose or corroded connector at the transmission is a far more common cause of an open circuit than a failed solenoid, so always inspect the pins and seals before condemning the solenoid.
  • The electronic pressure control solenoid shares a ground path with other transmission solenoids on many Mazda models, so a single bad ground can set P1746 alongside other solenoid codes.
  • After replacing the solenoid, the TCM may need a line pressure adaptation reset; skipping this step can leave the transmission shifting harshly and lead to a false comeback.
  • A shorted or open solenoid can sometimes test fine when cold but fail when hot, so resistance checks should be repeated after warming the transmission fluid.
  • P1746 does not always mean the solenoid itself is defective; a chafed wire inside the transmission pan from a previous repair is a frequent hidden cause.

Can I keep driving with P1746?

You can usually drive the vehicle to a repair shop, but avoid heavy acceleration and towing because the transmission may be in limp mode with elevated line pressure. If shifting becomes severely harsh or the vehicle refuses to move, stop driving and have it towed.

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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