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Home / DTC / P0704 — Clutch Switch Input Circuit Malfunction

P0704 — Clutch Switch Input Circuit Malfunction

Detailed page for trouble code P0704.

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Code

P0704

MERCEDES-BENZ P — Powertrain

Clutch Switch Input Circuit Malfunction

Brand: MERCEDES-BENZ
Type: P — Powertrain
AI status
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Page language: EN

Causes

  • Faulty clutch pedal position switch (mechanical wear or internal failure)
  • Open, shorted or corroded wiring harness in clutch switch circuit
  • Poor connector contact or bent/frayed terminal at switch or control module
  • Misadjusted or mechanically binding clutch pedal/switch actuator
  • Short to battery voltage or ground at the signal or reference circuit
  • Faulty transmission/engine control module (rare)

Symptoms

  • MIL/Check Engine lamp on
  • Engine may not crank/start if vehicle uses clutch-start interlock
  • Start/stop or cruise control may be disabled
  • Transmission may not enable gear changes or go into drive modes properly
  • Intermittent/noisy behavior of starting or shift control tied to clutch pedal operation

What to check

  • Retrieve freeze frame data and related codes with an OBD-II scanner
  • Visually inspect clutch pedal area: switch position, actuator, mounting and for mechanical binding
  • Inspect connector and wiring harness for corrosion, damage, exposed conductors, chafing or pin push-out
  • Check fuses and any related relays for the control circuits
  • Backprobe clutch switch connector while operating pedal to observe signal changes with scan tool or multimeter
  • Measure continuity and resistance between switch terminals and control module connector with ignition off

Signal parameters

  • Typical reference voltage to switch: approx. 5 V (varies by vehicle)
  • Closed-switch output: approx. 0–0.5 V (logic low) or continuity near 0 Ω
  • Open-switch output: approx. 4.5–5 V (logic high) or near infinite Ω
  • Expected switch state change: quick, stable transition when pedal moved through actuation point
  • If using oscilloscope: clean square/step transition with no excessive noise or bouncing

Diagnostic algorithm

  1. Connect a diagnostic scan tool; record P0704 and any related codes or freeze-frame data
  2. Perform a visual inspection of the clutch pedal switch, actuator, mounting and wiring for obvious damage
  3. With ignition ON (engine off) backprobe the switch connector and observe signal while an assistant operates the pedal. Verify signal toggles cleanly between expected voltages or continuity states
  4. Measure continuity between switch ground and vehicle ground; verify proper reference voltage present at switch reference pin
  5. If signal is missing or intermittent, wiggle test wiring and harness while monitoring signal to find breaks or intermittent connectors
  6. If wiring and connectors are good, bench-test or replace the switch and recheck operation
  7. If short to battery or ground is suspected, isolate and repair harness; repair or replace damaged wiring/connector as required
  8. After repairs, clear codes and perform repeat testing (operate pedal and verify signal, perform road/start checks) to confirm code does not return
  9. If all wiring and switch tests good and code persists, consider control module input circuit testing or module replacement as last resort

Likely causes

  • Failed clutch switch
  • Damaged connector or wiring at pedal harness
  • Corroded terminals or poor pin engagement
  • Switch out of adjustment or physically obstructed

Fault status

⚠️ Status
Clutch switch input circuit malfunction detected. Signal from clutch pedal switch is out of expected range, open, shorted, or intermittent. May prevent start or affect transmission control until repaired.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 0.5-2.0 hours

Similar codes

P0705 P0701 P0706 P0708
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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