Diagnostic Overview - Skim Secret Key Not Stored In Pcm (P0633)
If the default Secret Key HAS NOT BEEN transferred to the WCM/WIN the DTC can be fixed and cleared. If the default Secret Key HAS BEEN transferred to the WCM/WIN the fault cannot be corrected without replacing the WCM/WIN and Keys/FOBIKs. The default data gets transferred to the WCM/WIN when a "WCM/WIN Replaced" routine is run on a vehicle that has the P0633 fault due to default data in the PCM, but the DTC was cleared prior to the routine being initiated. Therefore, if P0633 is active it is IMPORTANT NOT TO ERASE THE DTC before attempting any repair on the vehicle. Replacing the PCM will not fix this condition. It is possible in some cases for the vehicle to start and run if a new Key/FOBIK was programmed to the default value in the WCM/WIN. In some, but not all instances, clearing the DTC and then programming a Key/FOBIK will allow the Key/FOBIK to operate. If the customer is in for a MIL on, and not for a Key/FOBIK concern, diagnose the other DTCs that are present causing the MIL and ignore the active P0633 since it will not turn on the MIL.
Important "WCM/WIN Replaced" Scan Tool Routine Info: When the "WCM/WIN Replaced" routine is initiated and the PIN is entered, the scan tool looks for an unlocked message from the WCM/WIN. If the unlocked message is seen, the scan tool determines that the WCM/WIN is new (new unique Secret Key stored). If it does not get the unlock message it determines that the WCM/WIN is not new (original Secret Key stored). After making this determination the routine will then take one of two paths depending on if there is an active P0633 fault present. This is why it is important NOT TO ERASE THE FAULT.
- Original WCM/WIN:
- If the scan tool does not see an active P0633
when the "WCM/WIN Replaced" routine is initiated it will transfer the Secret Key from the PCM to existing WCM/WIN. If the PCM has the default value stored it value will be transferred to the WCM/WIN which will cause all Keys/FOBIKs to be inoperative and stop working. NOTE:
Once this occurs, running the "PCM Replaced" or "WCM/WIN Replaced" routines will show a message that the data was successfully transferred but the default data is being sent back and forth. If this happens the vehicle cannot be fixed without replacing the WCM/WIN and Keys/FOBIKs.
NOTE:If the original PCM with the original Secret Key stored is available it could be re-connected to the vehicle and the original Secret Key could be transferred back to the WCM/WIN by running the "WCM/WIN Replaced" with the old PCM connected.
- If P0633 is active when the routine is initiated, the scan tool will prompt the original Secret Key stored in the WCM/WIN to transfer to the PCM.
- If the scan tool does not see an active P0633
when the "WCM/WIN Replaced" routine is initiated it will transfer the Secret Key from the PCM to existing WCM/WIN. If the PCM has the default value stored it value will be transferred to the WCM/WIN which will cause all Keys/FOBIKs to be inoperative and stop working.
- New WCM/WIN:
If a new WCM/WIN is being used as a replacement part, its unique Secret Key can be over-written with the stored back-up copy of the original Secret Key by transferring the back-up copy of the original Secret Key from the PCM to the replacement WCM/WIN. This permits the original Keys/FOBIKs to be retained.
- If the condition causing the P0633 is present but the active DTC was erased, the scan tool will not see an active P0633 when the routine is initiated. In this scenario the scan tool assumes the PCM has the original Secret Key stored and transfers the data from the PCM to the new WCM/WIN. This overwrites the valid data and will cause the new WCM/WIN to be inoperative. NOTE:
Once this occurs, running the "PCM Replaced" or "WCM/WIN Replaced" routines will show a message that the data was successfully transferred but the default data is being sent back and forth. If this happens the vehicle cannot be fixed without replacing the WCM/WIN and Keys/FOBIKs.
- If P0633 is active when the routine is initiated, the scan tool will request the unique Secret Key value in the new WCM/WIN be transferred to the PCM. The new unique Secret Key value transfers from the WCM/WIN to the PCM. This replaces the default Secret Key data in the PCM with new Secret Key data. On the next key cycle the P0633 should change to stored and new Keys/FOBIKs can be programmed.
- If the condition causing the P0633 is present but the active DTC was erased, the scan tool will not see an active P0633 when the routine is initiated. In this scenario the scan tool assumes the PCM has the original Secret Key stored and transfers the data from the PCM to the new WCM/WIN. This overwrites the valid data and will cause the new WCM/WIN to be inoperative.