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Home / DTC / P1606 — EEPROM fail

P1606 — EEPROM fail

Detailed page for trouble code P1606.

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Code

P1606

MITSUBISHI P — Powertrain

EEPROM fail

Brand: MITSUBISHI
Type: P — Powertrain
AI status
Completed
ready
Completed 100%
Page language: EN

Causes

  • Corroded/damaged ECU connector or wiring (power, ground, CAN/LIN lines)
  • Low or unstable battery voltage during ECU write/learn operations
  • Blown fuse or poor power supply to ECU
  • Water ingress or physical damage to ECU circuit board
  • Failed or degraded EEPROM chip inside the ECU
  • Interrupted or failed ECU software/programming update

Symptoms

  • Malfunction indicator lamp (MIL) ON and P1606 stored
  • Loss of learned values (idle adapts, transmission shift points, fuel trims) or repeated relearn requests
  • Intermittent or permanent no-start or crank issues if immobilizer or critical data corrupted
  • Communication errors with scan tool or inability to program ECU
  • Random drivability faults, unexpected limp-home mode, or erratic sensor/actuator behavior
  • Stored additional codes related to communication, KAM (keep-alive memory) or checksum errors

What to check

  • Verify battery state-of-charge and charging system health (12.6V+ at rest; >13.5V running)
  • Scan ECU and other modules; read all stored codes and freeze frame data
  • Check for manufacturer-specific ECU communication failure messages
  • Inspect ECU connectors and wiring for corrosion, bent pins, water intrusion, or heat damage
  • Check relevant fuses and relays for ECU power and ignition-switched supply
  • Measure ECU supply voltage and ground continuity at the ECU harness during key-on and cranking

Signal parameters

  • Battery voltage (key ON and while programming)
  • Ignition-switched +12V feed to ECU
  • ECU main ground continuity / resistance to chassis (
  • CAN/LIN bus traffic and error counters
  • EEPROM status/flags and internal checksum values (OEM tool)
  • Keep-Alive Memory (KAM) contents and last-write timestamps (OEM tool)

Diagnostic algorithm

  1. Record all codes and freeze-frame data from all modules. Do not clear codes yet.
  2. Verify battery fully charged and good; ensure stable power during all tests and programming. Use battery charger if required.
  3. Visually inspect ECU connectors and wiring; repair any corrosion, broken pins, or damaged insulation. Wiggle harness while monitoring for changes in live data or codes.
  4. Check fuses/relays supplying the ECU and measure 12V and ground at the ECU connector with key ON and during cranking.
  5. Use an OEM-level scan tool to view EEPROM/memory status, checksum info, and any manufacturer-specific failure logs. Note whether the ECU accepts communication or programming commands.
  6. If communications work, attempt a software reflash or checksum repair with OEM tool following manufacturer procedures. Ensure stable power during reflash. Back up original calibration/data if possible.
  7. If reflash fails or EEPROM reports hardware failure, consider ECU repair (EEPROM chip replacement or PCB-level repair by a specialist) or module replacement. Follow immobilizer pairing/anti-theft relearn procedures after replacement.
  8. After repair or reflash, clear codes, perform required relearns/adaptations, road test and re-scan to confirm no return of P1606 and related faults.
  9. If intermittent and no ECU fault found, inspect other modules (immobilizer, BCM), vehicle grounds, and recent aftermarket installations for causes of voltage spikes or interruptions.

Likely causes

  • Internal EEPROM chip failure in ECU
  • Poor power or ground to ECU (intermittent supply during writes)
  • Corroded ECU connectors or PCB damage from moisture
  • Failed ECU following an interrupted reflash/programming attempt

Fault status

⚠️ Status
EEPROM read/write or checksum error detected in ECU – memory corruption or failed non-volatile storage.
🔴 Repair difficulty: Hard
⏱️ Diagnostic time: 1-4 hours

Similar codes

P0600 P0601 P0602 P0603 P0606 P1604
406

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