Code
P0762
MERCEDES-BENZ
P — Powertrain
Shift Solenoid C Stuck On
Views:
UK: 10
EN: 17
RU: 15
AI status
Completed
Completed
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Causes
- Sticking or mechanically seized shift solenoid C inside the valve body
- Short circuit to power in the solenoid harness or connector
- Wiring open/short or poor connector pin contact
- Contaminated or degraded transmission fluid causing solenoid sticking
- Faulty TCM/PCM driver output or internal electronic failure
- Hydraulic valve body contamination or wear
Symptoms
- Harsh, delayed, or abnormal up/down shifts
- Transmission stuck in a single gear or limp mode
- Check Engine / transmission warning lamp illuminated
- Erratic shift behavior (hunting between gears)
- Unusual transmission noise when shifting
- Reduced drivability and possible loss of torque converter lockup
What to check
- Read freeze frame and live data with a Mercedes-capable scan tool; note transmission temperature and shift events
- Check transmission fluid level, condition and color; look for metal particles or burnt smell
- Visually inspect wiring harness and connector for solenoid C for damage, corrosion, or loose pins
- Backprobe solenoid C connector to measure voltage and duty cycle while commanded ON/OFF
- Measure solenoid coil resistance and compare to factory specification
- Perform an active test (command solenoid ON/OFF) with scan tool while monitoring response
Signal parameters
- Idle/OFF state expected: near 0 V or open circuit at solenoid control (model dependent)
- Activated/ON state expected: pulsed or steady voltage near battery (approx. 8–14 V when driven high) or PWM duty cycle as commanded by TCM
- Coil resistance: varies by application; commonly tens of ohms (check OEM spec) — an open or very low value indicates fault
- PWM frequency: typically tens to a few hundred Hz (varies by model); duty cycle varies 0–100% depending on commanded valve position
- Response: solenoid should change state quickly when commanded (milliseconds to a few hundred ms)
Diagnostic algorithm
- Retrieve codes and freeze frame; note transmission temp and driving conditions when fault set.
- Inspect transmission fluid level and condition; top or replace fluid if contaminated and consider filter change.
- Visually inspect connector and harness for solenoid C. Repair any damaged wiring or corrosion; ensure secure connector seating.
- With ignition ON (engine off) backprobe the solenoid connector: measure coil resistance and compare to spec.
- Use scan tool to command solenoid C ON/OFF while monitoring voltage/duty cycle at the connector to confirm TCM output and wiring integrity.
- If wiring and TCM output are correct but solenoid behavior remains stuck ON, bench-test or swap solenoid C with another known-good solenoid (if practical) to confirm solenoid mechanical/electrical failure.
- If solenoid is faulty or valve body contamination is evident, remove valve body or solenoid pack for cleaning or replacement per factory procedure. Replace filter and fluid.
- After repair, clear codes, perform transmission relearn/adapt procedures required by Mercedes, and road-test to verify normal operation.
- If electrical driver from TCM is suspected (no proper output yet wiring and solenoid OK), verify TCM grounds/power and consider module diagnostics or replacement per factory guidance.
Likely causes
- Contaminated fluid with debris causing solenoid C to stick
- Damaged wiring (chafing, corrosion) to solenoid C causing a power short
- Failed solenoid coil (internal short) that reads as constantly ON
- Poor connector connection (corrosion, bent pins) at solenoid plug
- Valve body internal valve sticking or spring failure
- Faulty TCM driver circuit (less common)
Fault status
Status
TCM reports Shift Solenoid C circuit stuck ON (continuous activation detected). Check solenoid, wiring, fluid/valve body, and TCM outputs.
Repair difficulty: Medium
Diagnostic time: 1–4 hours
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