P0633 code meaning
Immobilizer Key Not Programmed ECM/PCM
What P0633 means
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.
P0633 at a glance
- Check engine lightUsually not
- Emissions testNot an emissions code
- Limp modeNot expected
- Repair difficultyMedium
- Typical labor0.5 to 1.5 hours
- Clears after repairWhen cleared with a scanner
Symptoms of P0633
- 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
Common causes of P0633
- Most likelyEngine module replaced, immobiliser not learned
- PossibleLearn procedure aborted or learn mode not exited (no start for another reason)
- PossibleCommunication fault to the immobiliser module
- Less likelyEngine module software fault (false setting)
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Engine control moduleImmobilizer module
What each part of P0633 means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 0 | Generic code: it means the same on every make (SAE standard). |
| 6 | Area: computer (engine control module) and output circuits. |
| 33 | The exact fault in that area. |
What to do next
- Note P0633 and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about P0633
What does P0633 mean?
P0633 means "Immobilizer Key Not Programmed ECM/PCM". 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. It is a generic code, so it means the same on every make.
Is it safe to drive with P0633?
P0633 does not normally turn on the check engine light by itself. Watch for the symptoms above and have it checked soon.
Will P0633 fail an emissions test?
P0633 is not an emissions code, so on its own it usually does not fail an emissions test. Other stored codes or a lit check engine light still can.
How hard is P0633 to fix?
Difficulty: medium. A typical repair takes 0.5 to 1.5 hours of work. This is a job for a workshop.
Will P0633 clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.