P1735 — Mazda — First Gear Switch Circuit Failure

P1735 (Mazda): First Gear Switch Circuit Failure — what it means, the affected system and what to check before replacing parts.

Meaning, symptoms, causes and checks

First Gear Switch Circuit Failure. Source catalogue definition; confirm applicability using vehicle service information.

Affected system: Powertrain

Symptoms

  • Vehicle fails to engage first gear
  • Transmission stuck in limp mode
  • Check Engine Light illuminated
  • Erratic shifting behavior
  • Loss of power during initial acceleration

Possible causes

  • Defective first gear position switch
  • Short circuit or open circuit in transmission wiring harness
  • Corroded electrical connectors at the transmission control module
  • Faulty transmission control module (TCM)
  • Mechanical failure of the internal shift selector

What to check

  • Inspect transmission wiring harness for physical damage or moisture
  • Verify electrical resistance of the first gear switch using a multimeter
  • Check connector pins for oxidation or bent terminals
  • Scan transmission control module for additional related fault codes
  • Perform a road test to monitor gear engagement signals via diagnostic software