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Home / DTC / P0755 — Shift Solenoid B Malfunction

P0755 — Shift Solenoid B Malfunction

Detailed page for trouble code P0755.

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Code

P0755

MERCEDES-BENZ P — Powertrain

Shift Solenoid B Malfunction

Brand: MERCEDES-BENZ
Type: P — Powertrain
AI status
Completed
ready
Completed 100%
Page language: EN

Causes

  • Failed or sticking shift solenoid B (internal coil or valve)
  • Open or short in solenoid B wiring or connector
  • Corroded or loose transmission harness/connector
  • Faulty TCM/transmission control driver
  • Contaminated or low transmission fluid causing solenoid/valve sticking
  • Valve body hydraulic fault

Symptoms

  • MIL (Check Engine Light) illuminated
  • Transmission may be stuck in one gear or shift improperly
  • Harsh, delayed or erratic shifting
  • Transmission may enter limp-in/safe mode
  • Stored transmission-related trouble codes
  • Possible transmission slipping under load

What to check

  • Read and record freeze frame data and all transmission codes with a capable scan tool
  • Check transmission fluid level, condition, and smell for contamination/burning
  • Visual inspection of solenoid connector and wiring for damage, corrosion or loose pins
  • Backprobe solenoid connector and measure resistance across solenoid coil
  • Check for proper supply voltage (battery voltage) at solenoid connector with key ON
  • Inspect/verify good ground at transmission wiring harness

Signal parameters

  • Solenoid coil resistance (typical): roughly 6–30 ohms (manufacturer-specific — verify spec)
  • Supply voltage when energized: ~11–14 V (battery voltage) or PWM drive from TCM
  • Off voltage: ~0 V (or floating depending on driver), check with reference to battery and ground
  • PWM control: duty cycle varies 0–100% depending on commanded pressure; frequency commonly in the tens to a few hundred Hz
  • Current draw: commonly 0.2–2 A when energized (varies by solenoid design)

Diagnostic algorithm

  1. Retrieve all codes and freeze-frame data using a transmission-capable scan tool. Note related codes and vehicle symptoms.
  2. Verify transmission fluid level and condition. If fluid is very dirty or contaminated, consider fluid/filter service before further electrical diagnosis.
  3. Visually inspect wiring and connector for solenoid B: look for corrosion, bent pins, damaged insulation, or evidence of water ingress.
  4. With ignition ON (engine off), backprobe solenoid B connector and measure coil resistance. Compare to spec. An open or very low resistance indicates a bad coil.
  5. With key ON, verify battery voltage is present at the supply terminal of the solenoid connector. Check for a good ground reference.
  6. Using a scan tool with bi-directional control, command solenoid B on/off while monitoring voltage/ground at the connector. Observe response and watch for PWM signal and duty change.
  7. If no command response or abnormal readings, perform continuity checks from the solenoid connector to the TCM connector to locate opens/shorts. Repair any wiring faults found.
  8. If wiring and connector are good but solenoid shows abnormal resistance or does not actuate when properly powered, replace the solenoid (or solenoid pack/valve body as required).
  9. If solenoid replacement does not clear the fault, suspect a faulty TCM output driver. Confirm by isolating wiring and bench-testing or substitute known-good TCM if available.
  10. After repairs, clear codes, run transmission through all gears (or use scan tool active tests) and road test. Confirm proper operation and that the P0755 does not return. Perform any required TCM adaptations/relearns per manufacturer procedure.

Likely causes

  • Damaged wiring harness or connector to shift solenoid B
  • Solenoid coil out of specified resistance (open/short)
  • Contaminated fluid or debris in valve body preventing valve movement
  • Poor ground or intermittent connector contact
  • Faulty TCM driver output (less common)

Fault status

⚠️ Status
TCM detected an electrical or functional fault in Shift Solenoid B circuit (open, short, stuck or incorrect feedback). Fault set when circuit behavior is outside expected parameters during commanded operation.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 1.0-3.0 hours

Similar codes

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856

Browse 856 MERCEDES-BENZ manuals: repair procedures, diagnostics, wiring diagrams, component locations, service data and Labor Times by year, model and trim.

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