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Home / DTC / P1696 — PCM Failure EEPROM Write Denied

P1696 — PCM Failure EEPROM Write Denied

Detailed page for trouble code P1696.

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Code

P1696

MITSUBISHI P — Powertrain

PCM Failure EEPROM Write Denied

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

Causes

  • Low or unstable battery/charging voltage during PCM write operations
  • Poor or corroded power or ground connections to the PCM
  • Blown PCM power or ignition feed fuses
  • Damaged, corroded, bent or loose PCM connectors or pins
  • Internal PCM/EEPROM memory failure or corruption
  • Failed or incomplete PCM reflash or aftermarket programming attempt

Symptoms

  • Malfunction indicator lamp (MIL) illuminated
  • Vehicle may store multiple PCM-related or communication DTCs
  • Loss of adaptive memory or driveability adaptations (rough idle, hesitation)
  • Inability to complete PCM reprogramming or write procedures
  • Intermittent starting or stall events if critical parameters are corrupted
  • Some modules may not communicate or report expected values

What to check

  • Verify battery state-of-charge (fully charged) and health; inspect battery terminals for corrosion and tightness
  • Check charging system voltage with engine running (should be ~13.5–14.8 V)
  • Inspect and test PCM power and ground circuits, measure voltage at PCM power pins with key ON and engine running
  • Check for and replace any related fuses or relays supplying the PCM
  • Visually inspect PCM connector and pins for corrosion, bent pins, water intrusion or damage
  • Connect a quality scan tool and confirm reliable communication with the PCM; read freeze frame and full stored codes

Signal parameters

  • Battery voltage (ignition ON, engine off): approx. 12.4–12.8 V expected
  • Charging voltage (engine running): 13.5–14.8 V expected
  • PCM supply & ground: stable presence of battery voltage on power pins and near-zero ohms to chassis ground on ground pins
  • CAN bus idle differential: roughly centered (~2.5 V each leg) with correct recessive level; verify network communication with other modules

Diagnostic algorithm

  1. Secure a fully charged battery or use a stable power supply/charger before any programming. Verify terminals and cables are clean and tight.
  2. With a scan tool, confirm P1696 and note any accompanying codes (communication, immobilizer, or internal memory codes). Attempt to read PCM identification and EEPROM/flash status if supported.
  3. Inspect fuses and relays for PCM power; replace any faulty items. Measure voltage at PCM supply pins with key ON and engine running.
  4. Inspect PCM connector and wiring for corrosion, damaged insulation, continuity and proper grounding. Repair any damaged wiring or connectors.
  5. Verify ground points for low resistance to battery negative; clean and tighten engine and chassis grounds.
  6. If communication is intermittent, isolate and repair CAN/K-line wiring faults; verify other modules see the PCM.
  7. If the vehicle was recently reflashed, confirm the reflash procedure completed and firmware is compatible. Repeat reflash/programming procedure following manufacturer instructions using a stable power source and correct tool/software.
  8. If EEPROM/flash read or write operations still fail and hardware evidence of external faults is eliminated, consider PCM internal failure. Refer to manufacturer guidance for repair/replace and immobilizer reprogramming. Replace PCM only after confirming it must be replaced and follow required programming/initialization steps.
  9. Clear codes and perform a road test; monitor for recurrence and check that adaptations/programmed values persist.

Likely causes

  • Weak battery or poor battery terminal connections during a recent reflash or adapt procedure
  • Faulty PCM supply fuse or relay
  • Water intrusion or physical damage to the PCM connector housing
  • Previous unsuccessful attempt to reprogram the PCM
  • Intermittent ground at the chassis/engine/ECM ground strap

Fault status

⚠️ Status
PCM EEPROM write denied — PCM write operation failed or was blocked (internal memory or external condition). Requires power/wiring verification and possible reprogram or PCM replacement.
🔴 Repair difficulty: Hard
⏱️ Diagnostic time: 2-6 hours

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