P0633 Immobilizer Key Not Programmed – ECM/PCM

Description and meaning of DTC p0633

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.

p0633 diagnostic trouble code symptoms

Symptoms of a P0633 trouble code may include:No start conditionLock/unlock functions may be disabledVehicle security system may be activatedOther diagnostic codes will likely be stored

DTC p0633 - possible causes

Causes for this code may include:Weak immobilizer key batteryImmobilizer key malfunctionImmobilizer key replaced without being programmedECM/PCM programming errorECM/PCM swapped between vehicles and/or replaced without being properly programmedECM/PCM failure

How to fix OBD-II diagnostic trouble code p0633

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 vehicle make and model, symptoms exhibited, and the code stored, it will help to steer you in the direction of a correct diagnosis. Note: There are multiple known TSBs, one for Dodge/Chrysler/Jeep vehicles #08-030-06, and one for GM vehicles #PIT4660B. By connecting the diagnostic scanner to the vehicle diagnostic port, you can tell if the ECM/PCM (and other controllers) is actually recognizing the immobilizer key. This information is typically presented as only a yes or no with no specific transponder description. If the ECM/PCM is not recognizing any immobilizer key, suspect that either the battery is dead in the key fob or that an incorrect immobilizer key is being used. If an inadvertent immobilizer key yes signal is displayed on the scanner display, suspect that the ECM/PCM has been replaced without programming it to match the vehicle. If this is not the case, you may suspect ECM/PCM failure or a programming error. In some cases, reprogrammed, aftermarket, replacement controllers and immobilizer keys may be purchased. If this is possible, you will need to provide the parts vendor with the mileage and VIN of the vehicle, as well as a secondary (factory programmed) immobilizer key. Replacement of any vehicle security system component or controller will usually require system reprogramming

More OBD-II diagnostic trouble codes (DTC)