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Home / DTC / P0604 — Internal Control Module Random Access Memory (RAM) Error

P0604 — Internal Control Module Random Access Memory (RAM) Error

Detailed page for trouble code P0604.

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Code

P0604

MERCEDES-BENZ P — Powertrain

Internal Control Module Random Access Memory (RAM) Error

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

Causes

  • Internal RAM corruption or failure within the control module
  • Corrupted calibration or firmware (software)
  • Low or unstable battery/charging system voltage during operation or programming
  • Intermittent or poor power/ground connections to the module
  • Water/contamination or physical damage to the module
  • Faulty replacement or improperly coded/reprogrammed control module

Symptoms

  • Malfunction Indicator Lamp (MIL) on with P0604 stored
  • Intermittent engine management faults, stalls or no-start conditions
  • Loss of some engine/transmission control functions or limp-home mode
  • Random or recurring drivability complaints that reset after battery disconnect or reprogramming
  • Communication errors to diagnostic tool or other modules (CAN messages missing)

What to check

  • Record all stored codes, freeze frame and freeze-data with a capable diagnostic tool (e.g., XENTRY, STAR DIAG)
  • Check battery state-of-charge, resting voltage and charging system (alternator) output
  • Visually inspect ECU connectors, wiring harness and ground points for corrosion, looseness or water damage
  • Check for recent programming or battery loss events (shop notes, owner history)
  • Attempt to read module software/calibration ID, software version and internal error counters
  • Search manufacturer TSBs and software updates related to P0604 or RAM errors

Signal parameters

  • Battery voltage at module (B+) — steady value while cranking and during operation
  • Ground integrity / resistance at module ground(s)
  • CAN or data-bus message activity and module transmit/receive status
  • Module internal status bytes, RAM/EEPROM error counters or self-test flags (from manufacturer tool)
  • Module uptime / reset count and last power-down event
  • Software/ECU part and calibration numbers (to detect mismatches)

Diagnostic algorithm

  1. Secure vehicle and record customer complaint and occurrence details. Note recent battery disconnects, jumps or software work.
  2. Retrieve and log all DTCs, freeze frame and module status with manufacturer-level scan tool.
  3. Check battery voltage and charging system; restore good battery/charging condition before further testing.
  4. Perform visual inspection of ECU: connectors, pins, wiring, ground strap and look for corrosion, water ingress or physical damage.
  5. If power/ground or connectors are suspect, repair and clear codes; retest to see if code returns.
  6. If wiring/power/ground is good, check software/calibration ID vs latest factory release and any applicable TSBs.
  7. Attempt to clear DTCs and perform a road/functional test. If code returns, attempt a controlled re-flash/reprogram of module software using manufacturer tool.
  8. After successful reprogram, re-check for DTCs. If reprogram fails or P0604 persists and all external wiring/voltage is verified, consider replacing the control module and program/configure per factory procedures.
  9. If module replacement is performed, follow required immobilizer/vehicle specific coding, pairing and programming steps using manufacturer equipment. Re-test vehicle and confirm issue resolution.

Likely causes

  • Failed ECU/PCM memory chips or internal electronics
  • Corrupted flash/firmware update left module in unstable state
  • Weak battery or failing alternator caused data corruption
  • Poor connector pins, corroded ground or damaged wiring to module power/ground terminals
  • Moisture ingress or mechanical shock to module housing
  • Incompatible aftermarket replacement ECU or incomplete coding/initialization

Fault status

⚠️ Status
Controller detected RAM/internal memory error or corruption in the control module.
🔴 Repair difficulty: Hard
⏱️ Diagnostic time: 1.5-4 hours

Similar codes

P0600 P0601 P0602 P0603 P0605
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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