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Home / DTC / P1739 — Primary pressure sensor open

P1739 — Primary pressure sensor open

Detailed page for trouble code P1739.

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Code

P1739

MITSUBISHI P — Powertrain

Primary pressure sensor open

Brand: MITSUBISHI
Type: P — Powertrain
AI status
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Page language: EN

Causes

  • Open or disconnected sensor connector
  • Broken, chafed or pinched wiring between sensor and TCM
  • Corroded or bent connector pins
  • Sensor internal failure (open element)
  • Blown fuse or loss of reference power/ground to sensor
  • Poor crimp or intermittent splice in harness

Symptoms

  • Transmission warning light / MIL or transmission lamp illuminated
  • Erratic shifting or harsh shifts
  • Transmission may enter limp/limitation mode or default gear
  • Loss of proper torque converter control or lockup
  • Stored DTC P1739 in transmission control module

What to check

  • Retrieve freeze-frame and live data with a scan tool; confirm P1739 and related codes
  • Visual inspection of sensor, connector and wiring for damage, contamination or corrosion
  • Check for secure mating and proper pin condition at sensor connector and TCM connector
  • Wiggle/pressure test wiring while monitoring for intermittent faults
  • Verify fuses and power/ground to transmission control circuits

Signal parameters

  • Typical primary pressure sensor uses a 5 V reference, ground and a signal return (consult model service manual for exact pins)
  • Expected signal behavior: voltage proportional to pressure — commonly in ~0.5–4.5 V range depending on pressure (model dependent)
  • Open-circuit symptom: signal voltage may read near 0 V or floating; an open will show no continuity to the sensor
  • Always verify exact voltage/resistance specifications from the vehicle service manual before testing

Diagnostic algorithm

  1. Confirm P1739 present and note any additional transmission or engine codes.
  2. Perform a thorough visual inspection of the primary pressure sensor and harness (look for damage, kinks, corrosion, fluid ingress).
  3. With ignition ON (engine OFF), backprobe the sensor connector: verify 5 V reference and ground presence. If missing, trace power/ground to the fuse/TCM.
  4. Measure sensor signal voltage at connector. If signal is ~0 V or open, check continuity from sensor signal pin to the TCM; repair any open wires.
  5. Perform an ohm/continuity test between sensor signal/ground pins and TCM pins to find opens or high resistance. Wiggle harness while monitoring for changes.
  6. If wiring and connectors are good but signal is absent or out of spec, replace the primary pressure sensor. Use OEM replacement and retest.
  7. If fault persists after sensor and wiring repair, inspect/repair TCM connector and consider TCM diagnostic/replacement per factory procedures.
  8. Clear codes and road test to confirm repair; re-scan to ensure no return of P1739.

Likely causes

  • Connector unplugged or corroded at the primary pressure sensor
  • Broken or shorted wire in harness (pull, pinch, rodent damage)
  • Internal sensor element open/faulty
  • Fault at TCM connector or TCM input circuit

Fault status

⚠️ Status
Primary pressure sensor open circuit detected — signal circuit shows no continuity or voltage. Transmission control module logged P1739.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 1.0-2.5 hours

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406

Browse 406 MITSUBISHI manuals: repair procedures, diagnostics, wiring diagrams, component locations, service data and Labor Times by year, model and trim.

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