What Does P1623 Mean?
The PCM attempted to write immobilizer security codes to memory but the operation failed. This indicates a problem with PCM internal memory or the key programming process.
Safety Warning
Vehicle will not start until immobilizer system is properly programmed. Creates stranding risk but no immediate safety hazard.
Common Causes
35%
Low or fluctuating battery voltage during key programming procedure
30%
PCM internal EEPROM memory failure or corruption
20%
Interrupted programming sequence from scan tool disconnection or communication error
10%
Incorrect programming procedure or incompatible scan tool software version
5%
Poor ground connection at PCM causing intermittent power during write operation
Diagnostic Steps
1
Step 1: Verify battery voltage is stable at 12.6V or higher and connect battery maintainer during programming
2
Step 2: Check all PCM power and ground connections for corrosion, looseness, or high resistance
3
Step 3: Verify scan tool is updated with latest software and security access credentials are current
4
Step 4: Review TSBs for known PCM memory or immobilizer programming issues specific to vehicle
5
Step 5: Attempt programming procedure again following manufacturer exact sequence - if fails multiple times, replace PCM
Estimated Repair Cost
$250 - $1,800
Parts + labor, varies by vehicle and location
The PCM attempted to write immobilizer security codes to memory but the operation failed. This indicates a problem with PCM internal memory or the key programming process.
The most common cause of P1623 (Immobilizer Code Word/ID Number Write Failure) is: Low or fluctuating battery voltage during key programming procedure
Typical repair costs for P1623 range from $250 to $1,800, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Vehicle will not start until immobilizer system is properly programmed. Creates stranding risk but no immediate safety hazard.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P1623 to identify the root cause.
OBDHut Mobile App
Scan codes directly from your car with the OBDHut app.
Coming Soon
Quick Info
Category
Powertrain
System
Anti-Theft/Security System
Difficulty
Type
Manufacturer
Recommended Tools
OBD2 Scanner
A quality scan tool helps you read codes, view live data, and clear faults.
