DTC 51, Pass-Key(R) Invalid Key Detection: Notes

PASS-Key(R) detection circuit is completed when ignition key with embedded resistor pellet is inserted into ignition lock cylinder. When contacts in ignition lock cylinder mate with contact on pellet, CCM compares resistance value of key pellet to valid resistance programmed into CCM.

If key resistor pellet is incorrect, no output will be present from CCM to theft deterrent relay or PCM for about 3 minutes. If key is inserted into ignition (correct or incorrect key) or ignition is turned on before 3 minute time period has elapsed, timer will reset to 3 minutes. Disconnecting battery will not clear timer. When battery is reconnected, timer will reset to 3 minutes.

DTC 51 will set when ignition is on and voltage level sampled at CCM PASS-Key(R) input is greater or less than valid voltage range stored in CCM, signaling an invalid PASS-Key(R) resistance. Extreme hot or cold ambient temperatures may cause DTC 51 to set, although this is highly unlikely. To eliminate this possibility, ensure vehicle and key are at room temperature when testing. Ensure key resistor contacts are clean and free from grease, oil, etc. Any contamination on contacts could cause code to set.

When DTC 51 is set:

• SECURITY indicator will illuminate.
• Crank enable and FEDS enable system processing will be disabled.
• For a period of time, sampling of PASS-Key(R) resistance is disabled.
• UTD system will not disarm if system is armed. DTC 51 will clear when ignition is on and CCM PASS-Key(R) input detects a valid PASS-Key(R) resistance.