P0633 Immobilizer Key Not Programmed – ECM/PCM
OBD-II Trouble Code Technical Description
Immobilizer Key Not Programmed – ECM/PCM
What does that mean?
This is a generic diagnostic trouble code (DTC) and applies to many OBD-II vehicles (1996-newer). That may include but is not limited to vehicles from Dodge, Ram, Chrysler, Jeep, Chevy, GMC, Cadillac, etc. Although generic, the exact repair steps may vary depending on year, make, model and powertrain configuration.
When a code P0633 is stored, it means that the engine control module (ECM) or powertrain control module (PCM) has detected an immobilizer key which it does not recognize.
The immobilizer key is used to prevent vehicle theft and eliminate the need to place an actual metal key in the door lock cylinders or ignition cylinder. A transponder is integrated into the immobilizer key fob. When the key fob is within a certain distance of the vehicle, the transponder emits a signal to the ECM/PCM and other controllers. Typically, when the transponder signal is received, the doors are unlocked and the push-to-start button is activated. When the immobilizer key is moved away from the vehicle, the doors lock and the push-to-start function is automatically deactivated. The immobilizer key transponder is powered by a small battery.
Each immobilizer key emits a unique transponder signal. In order for the on-board controllers to recognize the transponder signal, they must be programmed appropriately. The ECM/PCM and the security control module are responsible for engine starting and the body control module (BCM) is responsible for door and trunk lock/unlock related functions.
Obviously, when either an ECM/PCM or an immobilizer key is replaced, it will need to be programmed.
If the ECM/PCM fails to find or recognize an immobilizer key, and vehicle entry or start-up is attempted, a code P0633 will be stored and a malfunction indicator lamp (MIL) may be illuminated. The immobilizer key transponder signature is compared between the ECM/PCM and other controllers each time the security system is activated and the self-test function is energized.
Photo of a PCM with the cover removed:
What is the severity of this DTC?
A stored code P0633 should be categorized as severe. If the controllers fail to recognize the immobilizer key, important functions (engine start-up and door unlocking) could potentially be disabled.
What are some of the symptoms of the code?
Symptoms of a P0633 trouble code may include:
No start condition Lock/unlock functions may be disabled Vehicle security system may be activated Other diagnostic codes will likely be storedWhat are some of the common causes of the code?
Causes for this code may include:
Weak immobilizer key battery Immobilizer key malfunction Immobilizer key replaced without being programmed ECM/PCM programming error ECM/PCM swapped between vehicles and/or replaced without being properly programmed ECM/PCM failureWhat are some P0633 troubleshooting steps?
Due to the delicate nature of certain parameters which must be programmed into the related controllers (VIN and mileage), access to reprogramming equipment must be limited to qualified personnel. If controller replacement is required, making a successful repair will be impossible without the means to reprogram the controller in question.
Although the stored code P0633 may be attributed to controller failure or some type of a controller programming error, it is most likely due to an immobilizer key or transponder battery problem.
In order to arrive at an accurate diagnosis of a code P0633, you will need a diagnostic scanner and a reliable source of vehicle information.
Use the vehicle information source to search for applicable technical service bulletins (TSB). If you locate a TSB that matches the vehi
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