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Home / DTC / P1780 — Gear 2 incorrect ratio

P1780 — Gear 2 incorrect ratio

Detailed page for trouble code P1780.

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P1780

MITSUBISHI P — Powertrain

Gear 2 incorrect ratio

Brand: MITSUBISHI
Type: P — Powertrain
AI status
Completed
ready
Completed 100%
Page language: EN

Causes

  • Faulty shift solenoid(s) or solenoid harness/connector
  • Low, dirty, or incorrect transmission fluid
  • Internal hydraulic leaks or clogged valve body passages
  • Worn clutch pack or band for 2nd gear
  • Damaged planetary gearset or other mechanical damage
  • Faulty input or output speed sensor (incorrect speed signals)

Symptoms

  • MIL (Check Engine) lamp illuminated
  • Harsh, delayed, or missing 2nd gear shift
  • Transmission slips or flares when shifting into 2nd
  • Loss of acceleration or limp-in mode (reduced performance)
  • Unusual transmission noise or shudder during 2nd gear
  • Stored transmission-related diagnostic trouble codes

What to check

  • Read and record all stored Transmission and Engine DTCs and freeze frame data
  • Check transmission fluid level, color, and smell (burnt, contaminated)
  • Scan live data: input and output shaft speeds, calculated gear ratio, TCM commanded gear, solenoid status
  • Inspect wiring and connectors at transmission, solenoids, speed sensors, and TCM
  • Measure resistance of shift solenoids and compare to spec
  • Perform an actuator (solenoid) on/off test with a scan tool if available

Signal parameters

  • Input (transmission) speed sensor (RPM)
  • Output (vehicle) speed sensor (RPM)
  • Calculated gear ratio (input speed / output speed)
  • TCM commanded gear and shift status
  • Shift solenoid voltage and duty cycle
  • Shift solenoid resistance (ohms)

Diagnostic algorithm

  1. Retrieve all codes and freeze frame. Clear codes and perform a monitored road test to re-create P1780 and capture live data when shifting into 2nd gear.
  2. Check transmission fluid level and condition; top or replace fluid/filter if low or contaminated and re-test.
  3. Visually inspect wiring and connectors for damage, corrosion, or looseness at solenoids, speed sensors and TCM; repair as needed.
  4. Monitor input/output speed sensors and calculated gear ratio during a shift to 2nd. Confirm measured ratio deviates from expected range.
  5. Test shift solenoid(s): measure resistance, perform on/off actuation with a scan tool and verify response in live data. Replace faulty solenoid(s).
  6. If solenoids and wiring are good, perform transmission line pressure tests and compare to specifications to check for hydraulic faults.
  7. If hydraulic pressure is low or unstable, inspect valve body for sticking valves, clogged passages, or internal leaks; rebuild or replace valve body as indicated.
  8. If hydraulic and solenoid operation are correct, suspect internal mechanical wear (clutch pack, band, planetary gear). Perform internal inspection/repair or remove and overhaul transmission.
  9. After repairs, clear codes and perform thorough road test to verify normal 2nd gear ratio and that code does not return.

Likely causes

  • Contaminated or low transmission fluid causing improper hydraulic pressure
  • Faulty shift solenoid (stuck, electrically open/shorted or intermittently operating)
  • Wiring/connectors to solenoids or speed sensors are corroded or disconnected
  • Valve body sticking or internal leak in hydraulic circuits for 2nd gear
  • Worn clutch pack, band, or gearset causing incorrect gear ratio

Fault status

⚠️ Status
TCM detected 2nd gear ratio outside expected range. Possible causes include shift solenoid failure, low/contaminated transmission fluid, hydraulic leaks or valve body faults, worn clutches/bands, speed sensor or wiring faults. Further diagnosis required.
🔴 Repair difficulty: Hard
⏱️ Diagnostic time: 2-8 hours
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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