Code
P1696
PLYMOUTH
P — Powertrain
PCM Failure EEPROM Write Denied
Views:
UK: 24
EN: 50
RU: 56
AI status
Completed
Completed
100%
Causes
- Failed or corrupted PCM EEPROM (internal memory)
- Low or unstable battery/charging voltage during write
- Poor power or ground connections to the PCM
- Interrupted or failed reflash/programming attempt
- Security/immobilizer or module mismatch preventing write
- Faulty or incompatible scan/tool with insufficient permissions
Symptoms
- Malfunction Indicator Lamp (MIL) illuminated
- Stored P1696 plus other PCM or communication-related DTCs
- Vehicle may enter limp mode or have reduced functionality
- Failed or incomplete reflash/programming
- Intermittent drivability issues, erratic idle, or no-start in some cases
- Scan tool reports inability to write or adapt parameters to PCM
What to check
- Read and record all stored, pending, and freeze frame codes with an OEM-capable scan tool
- Check and record battery voltage (recommended ≥12.4 V; follow OEM spec) and charging system operation
- Inspect PCM power and ground connectors for corrosion, damage, or loose pins
- Verify correct scan tool and software version; confirm programming procedure and security access
- Check vehicle for additional module communication errors (CAN/BUS faults)
- Review service bulletins/TSBs for manufacturer-specific reflash procedures or known PCM issues
Signal parameters
- Battery voltage at PCM during write/program operation (V)
- Primary PCM supply current draw (A) during wake and programming
- CAN/K-line communication status and error counters during attempt
- EEPROM error/fault flags and internal write attempt counters (if readable)
- Ignition status and key/immobilizer state during programming
- Bus voltage and CAN bus load (presence of bus-off or error frames)
Diagnostic algorithm
- Record all codes and freeze frame data. Do not assume P1696 is the root cause; check for related faults.
- Verify and, if needed, charge the battery to a full state of charge. Ensure charging system is functioning before any reflash.
- Inspect PCM connectors, wiring, and grounds. Repair any corrosion, damaged pins, or poor connections.
- Check for other module communication errors on CAN/diagnostic bus. Resolve any bus faults first.
- Confirm the correct OEM programming procedure, software/calibration part number, and security access is available for the vehicle.
- Attempt to clear codes and reproduce. If code returns only during/after a programming attempt, retry reflash with a stable power supply and OEM tool.
- If reflash fails repeatedly, capture programming tool logs/messages. Try programming with dealer-level equipment or known-good programmer.
- If EEPROM write continues to be denied and programming tools report internal memory faults, consider PCM repair or replacement per OEM guidelines and reprogram replacement PCM to vehicle (immobilizer pairing as required).
- After repair/reprogram, verify no new memory errors and confirm all systems operate normally; clear codes and road test.
Likely causes
- Battery voltage dropped below required threshold during programming
- Attempted ECU reflash with non-OEM or incorrect software
- PCM internal EEPROM wear or corruption
- Lost communication between programming tool and PCM (CAN/K-line interruption)
- PCM ground or power circuit intermittent
Fault status
Status
PCM reported EEPROM write denied — programming or memory write failed; verify power, wiring, and reflash procedure before replacing module.
Repair difficulty: Hard
Diagnostic time: 2-4 hours
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