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Home / DTC / P0780 — Shift Malfunction

P0780 — Shift Malfunction

Detailed page for trouble code P0780.

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Code

P0780

MERCEDES-BENZ P — Powertrain

Shift Malfunction

Brand: MERCEDES-BENZ
Type: P — Powertrain
Views: UK: 22 EN: 67 RU: 41
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Page language: EN

Causes

  • Low, contaminated or incorrect automatic transmission fluid (ATF)
  • Faulty transmission shift solenoids or mechatronics unit (valve body)
  • Wiring harness fault, poor connector or ground at the TCM/transmission
  • Faulty gear range or position sensor (park/neutral switch)
  • Internal mechanical wear (clutch packs, bands, planetary gearset)
  • Faulty or misprogrammed TCM/TCU software

Symptoms

  • MIL/Check Engine light illuminated and transmission fault lamp
  • Harsh, delayed, or erratic upshifts or downshifts
  • Transmission stuck in one gear or shifts into limp/safe mode
  • Gear indicator not matching actual drive ratio
  • Transmission slipping, loss of drive or reduced performance
  • Possible unusual transmission noises during shift events

What to check

  • Read stored and pending DTCs and freeze frame with a Mercedes-capable scan tool
  • Check for related codes (solenoid, speed sensors, TCM communication)
  • Visually inspect wiring, connectors and grounding points at the transmission and TCM
  • Check battery voltage and charging system under load
  • Check ATF level, color and smell; replace or top up only to factory spec
  • Perform road test while monitoring live data (requested gear vs actual gear, speeds, solenoid commands)

Signal parameters

  • Requested gear / selected gear (TCM command)
  • Actual gear / gear ratio indication
  • Transmission input (turbine) speed and output (vehicle) speed
  • Line pressure (kPa or bar) and torque converter pressure
  • Shift solenoid command (duty cycle) and solenoid current/resistance
  • Clutch pressure sensors or actuator pressures (if equipped)

Diagnostic algorithm

  1. Retrieve all DTCs and freeze frame data with a Mercedes‑capable scan tool; record related transmission codes.
  2. Clear codes and attempt to re‑create the fault with a monitored road test. Note when/under what conditions the code returns.
  3. Check ATF level, color and smell. Correct fluid level and condition if out of spec. Replace fluid and filter if contaminated or burnt.
  4. Visually inspect transmission connector(s), wiring harness for damage, corrosion, pin push‑out and confirm good grounds. Wiggle test while monitoring live data for intermittent faults.
  5. Monitor live data: compare TCM requested gear vs actual gear/speed sensors; watch solenoid command duty vs measured response.
  6. Measure shift solenoid resistances at the transmission and compare to manufacturer specifications; check solenoid circuits for short/open to battery and ground.
  7. If available, measure dynamic line pressure with a gauge while performing commanded shifts to verify hydraulic actuation.
  8. Check input and output speed sensors for correct signals and phasing; replace sensors as required.
  9. Review TCM software level and Mercedes Technical Service Bulletins (TSBs); perform reprogramming/calibration if recommended.
  10. If electrical and hydraulic tests are within spec but malfunction persists, consider mechatronics/valve body replacement or TCM replacement as a final step. Follow Mercedes diagnostic and repair procedures; replacement may require programming and adaptation.

Likely causes

  • Incorrect ATF level or contaminated fluid
  • Electrical fault to shift solenoids or mechatronics connector
  • Failing shift solenoid(s) or internal valve body/mechatronics
  • TCM software or communication error
  • Mechanical wear causing inability to engage gear

Fault status

⚠️ Status
P0780 — Shift Malfunction. TCM detected incorrect or failed shift event; transmission may enter limp mode. Inspect fluid, wiring, solenoids, mechatronics and TCM software.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 2.0-6.0 hours

Similar codes

P0700 P0705 P0715 P0730 P0750 P0751
133

Browse 133 MERCEDES-BENZ manuals: repair procedures, diagnostics, wiring diagrams, component locations, service data and Labor Times by year, model and trim.

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