Fault code P0633 is called “Immobilizer Key Not Programmed – ECM/PCM” but in different programs it may be called differently. This fault designation applies to all vehicles equipped with OBD-II.
Technical description and explained code P0633
The stored code P0633 means that the control module (PCM) or (ECM) has detected an immobilizer key that it does not recognize. Other controllers may also detect incorrect or non-existent readings from the immobilizer.
The immobilizer key is used to prevent the theft of the vehicle and eliminates the need to lock the door locks manually. The immobilizer key fob has a transponder built in, when you are at a certain distance from the car, it transmits a signal to the ECM/PCM.
Typically, when the transponder signal is received, the doors unlock and the engine start button is activated. When the immobilizer key is removed from the vehicle, the doors are locked and the start button function is automatically deactivated.
Each immobilizer key emits a unique transponder signal. In order for the on-board controllers to recognize the transponder signal, they must be programmed accordingly.
If the ECM/PCM or immobilizer key is replaced, they must be programmed.
If the ECM/PCM cannot find or recognize the immobilizer key, code P0633 will be stored and the malfunction indicator lamp (MIL) may illuminate. The immobilizer key transponder signature is compared between the ECM/PCM and the other controllers each time the alarm system is activated and the self-diagnostic function is enabled.
Symptoms of vehicle malfunctions
The main signal that an error P0633 has occurred is the Malfunction Indicator Lamp (MIL) is also known as the CheckEngine Light.
It can also be warning signs such as:
- The “Check engine” control lamp on the control panel will light up (the code will be stored as a fault).
- Other related fault codes may also be present.
- Unable to start the engine.
- Disable vehicle lockout and unlock functions.
- Activation of the vehicle security system.
Stored fault code P0633 should be categorized as serious, as the ECM/PCM does not recognize the immobilizer key. For this reason, important functions such as engine start and door unlocking will be disabled.
Factors that can cause this error code
The error code P0633 can mean that one or more of the following problems have occurred:
- ECM/PCM programming error.
- Replacement of ECM/PCM from another vehicle without proper programming.
- Faulty immobilizer key.
- The immobilizer key is replaced without programming.
- Dead battery in the immobilizer key.
- Sometimes the cause is the ECM/PCM module itself.
How to fix or reset OBD-2 code P0633
Some suggested steps for troubleshooting and fix the error code P0633:
- Read all stored data and error codes with an OBD-II scan tool. To find out when and under what circumstances error P0633 appeared.
- Check the power supply in the immobilizer key as well as the key itself for proper operation.
- Use the scanner to check how the immobilizer key is perceived by the ECM/PCM.
- If it is not displayed when the key is working properly, look for a problem with the ECM/PCM.
Diagnose and repair of problems
Unlike most other stored codes, P0633 is usually related to an ECM/PCM fault or programming error. Without the ability to properly reprogram the controller, successful repair will be unlikely.
Diagnosing this code will require a diagnostic scanner and a source of vehicle information. It is necessary to connect the scanner to the vehicle’s diagnostic port and check how the immobilizer key is perceived by the ECM/PCM.
This information is usually presented as “yes” or “no” without a description of the specific transponder. If the ECM/PCM does not recognize any immobilizer key, the battery in the key fob may be dead or the wrong immobilizer key is being used.
If the scan tool display shows an occasional “yes” immobilizer key signal, the ECM/PCM may have been replaced without programming to match the vehicle. Sometimes an ECM/PCM failure or programming error occurs.
The main problem with the occurrence of error P0633 is the replacement of the controller or immobilizer key without proper programming and adaptation to the specific vehicle.
On which vehicles does this problem occur most frequently
Fault code P0633 can occur on different vehicles but there are statistics on which brands this occurs most often. Here is a list of some of them:
- Cadillac
- Chevrolet (Captiva, Cruze, Silverado)
- Chrysler
- Dodge (RAM)
- GMC
- Jeep
- Mercedes-Benz
- Opel (Corsa)
- Saab (9-3)
- Ssangyong (Actyon)
Fault code P0633 can sometimes be found with other errors. The most common are the following: P0541, P0630, P0631, P0632, P0638, P2607.
