The immobiliser couples the engine module to the immobiliser control module (GM body module, Chrysler SKIM/WCM) through a secret key and a challenge-response exchange – 'key' here means these security data, not the ignition key. P0633 means the engine module has not learned this secret key yet. At GM and Saab the code is set automatically whenever the engine module enters learn mode, for example as a new part, and clears after a successful learn and engine start; it is only a real fault if learn mode does not end, often because the engine fails to start for another reason. Chrysler calls it 'SKIM secret key not stored in PCM' and fixed false settings on the 2012–13 Grand Voyager 2.8 diesel by software. The engine does not start or dies after one or two seconds; the security lamp, not the check engine light, comes on.
Medium severity. Can I keep driving?If it starts normally you can keep driving, but avoid stopping anywhere you could not get help, because it might not restart.
Symptoms
- Engine does not start or dies immediately
- Security or immobiliser lamp on or flashing
- Code present after engine module replacement until learned
- Sometimes immobiliser communication codes
Most likely causes
- Engine module replaced, immobiliser not learned
- Learn procedure aborted or learn mode not exited (no start for another reason)
- Communication fault to the immobiliser module
- Engine module software fault (false setting)
What to check, in order
Start with the simplest. You can tick off each step.
Good to know
- Repair difficulty: medium
What each character of P0633 means
- P: Powertrain: engine and transmission
- 0: Generic code: same on every make
- 6: Control modules and outputs
- 33: Specific fault in that system
Frequently asked questions
Can I keep driving with code P0633?
If it starts normally you can keep driving, but avoid stopping anywhere you could not get help, because it might not restart.
What causes code P0633?
The most common causes are: engine module replaced, immobiliser not learned; learn procedure aborted or learn mode not exited (no start for another reason); communication fault to the immobiliser module.
Related codes
- P0513Incorrect Immobilizer Key
- P0630VIN Not Programmed or Incompatible ECM/PCM
- P0602Control Module Programming Error
- P0610Control Module Vehicle Options Error
Sources
- law.cornell.edu: 13 CCR 1968.2
- saabwisonline.com: dtc p0633
- saabwisonline.com: dtc p0633
- static.nhtsa.gov: MC 10136868 9999
Values and procedures vary by manufacturer. If it affects brakes, steering, fuel or high voltage, see a professional. Updated: 2026-11-04. How we build these pages.