P1621 — Control Module Long Term Memory Performance/ Immobilizer Code Words Do Not Match

What Does P1621 Mean?

P1621 is a manufacturer-specific diagnostic trouble code: Control Module Long Term Memory Performance/ Immobilizer Code Words Do Not Match. This code applies to OTHER, VOLKSWAGEN, MAZDA, BUICK, CADILLAC vehicles. Unlike generic OBD-II codes, manufacturer-specific codes are defined by the vehicle maker and may only apply to certain makes and models.

Symptoms of P1621

⚠️ Check Engine Light (MIL) illuminated
⚠️ Control Module Long Term Memory not meeting expected output
⚠️ Degraded performance of related system
⚠️ Reduced engine performance

Common Causes

🔍 Control Module Long Term Memory degraded from age or contamination
🔍 Mechanical wear in Control Module Long Term Memory or related parts
🔍 Restriction or blockage affecting Control Module Long Term Memory
🔍 Calibration drift in Control Module Long Term Memory

Frequently Asked Questions

What does P1621 mean?

P1621 indicates: Control Module Long Term Memory Performance/ Immobilizer Code Words Do Not Match. The vehicle's computer has detected that the Control Module Long Term Memory is not operating within its expected parameters and stored this diagnostic trouble code.

Can I drive with code P1621?

You can drive short distances for essential trips, but schedule a diagnosis soon. Driving with P1621 for extended periods may cause additional problems.

How much does it cost to fix P1621?

Repair costs for P1621 typically range from $50 to $400, depending on the root cause. Simple wiring or connector repairs are on the lower end, while component replacement costs more. A proper diagnosis ($80–$150 at most shops) will identify the exact cause before committing to expensive parts.

What To Do Next

Possible Fixes

🔧 Inspect Control Module Long Term Memory for contamination or wear
🔧 Replace Control Module Long Term Memory
🔧 Address any related mechanical faults

1
Find your vehicle above
Click your make and model for real owner reports and common causes specific to your vehicle.
2
Check for recalls
Go to nhtsa.gov/recalls and enter your VIN. Free repairs if covered.
3
Get a professional diagnosis
A code alone doesn't identify the exact failed part. A diagnostic ($50–$150) pinpoints the root cause.

P1621: Control Module Long Term Memory Performance/ Immobilizer Code Words Do Not Match