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DTC codes / Mitsubishi codes / P1696

P1696 · MitsubishiPCM Failure EEPROM Write Denied

P1696 on a Mitsubishi means the powertrain control module (PCM) tried to write data to its internal electrically erasable programmable read-only memory (EEPROM) and the write was denied. The PCM uses this memory to store learned values, immobilizer data and fault history, so a denied write points to a memory or internal PCM problem rather than a sensor fault.

SystemPowertrain
Code typeMitsubishi specific
SeverityMedium
Fix difficultyProfessional
AreaComputer and output circuits

Symptoms you may notice

  • Malfunction indicator lamp (MIL) illuminated, often with no other symptoms
  • Intermittent no-start or crank-no-start condition, especially after battery disconnect or PCM replacement
  • Immobilizer or security light staying on or flashing when the key is turned
  • Rough running or poor driveability if the PCM cannot store learned fuel and idle values
  • Stored diagnostic trouble codes that will not clear or return immediately after clearing
  • Occasional electrical oddities such as erratic gauge readings or accessory glitches

Common causes, most likely first

  1. Internal PCM EEPROM failure or corrupted memory block
  2. Low or unstable battery voltage during a write event, such as cranking with a weak battery
  3. Poor ground or power supply connection at the PCM connectors or chassis grounds
  4. Aftermarket reflash or tuning attempt that was interrupted or rejected by the PCM
  5. Immobilizer or key coding procedure interrupted before completion
  6. Water intrusion or corrosion at the PCM connector pins
  7. PCM replacement or reprogramming performed without the correct Mitsubishi procedure

How to diagnose and fix it

  1. Record all stored codes and freeze-frame data before clearing anything, then verify battery voltage and charging system output
  2. Inspect PCM connectors and chassis grounds for corrosion, loose pins or water intrusion and repair as needed
  3. Clear the code and perform a battery disconnect relearn to see whether the fault returns immediately
  4. Check for any aftermarket programming or immobilizer work and restore the PCM to stock calibration using a Mitsubishi-capable scan tool
  5. Run the manufacturer's PCM self-test and EEPROM write test with a factory-level diagnostic tool
  6. If the write-denied condition persists with good power and grounds, replace and reprogram the PCM following Mitsubishi's immobilizer matching procedure
  7. Road test and recheck that the code does not reset after several key cycles

Why this code is rarely a sensor fault

  • A denied EEPROM write is an internal PCM event, so replacing sensors or actuators will not fix it and often wastes money
  • A weak battery that drops voltage during cranking is a common trigger because the PCM aborts memory writes when supply voltage falls below its threshold
  • Aftermarket performance tunes and piggyback modules frequently cause this code by interrupting or corrupting the PCM write process
  • The code can appear after a failed immobilizer key programming session even though the engine still starts normally
  • Corroded ground straps on Mitsubishi models are a frequent hidden cause of intermittent PCM memory faults that only appear in damp weather

Can I keep driving with P1696?

The vehicle is usually safe to drive if it starts and runs normally, but avoid repeated key cycles and do not disconnect the battery until the fault is diagnosed. If the engine cranks without starting or the immobilizer light stays on, stop driving and have the PCM circuit checked.

Tools that help

Tools we recommend are in the Auto Veteran shop on Amazon. As an Amazon Associate we earn from qualifying purchases.

Guidance is general and written for Mitsubishi vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.

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