For 1990-2009 cars

When a key is inserted in the ignition, contacts that are located in the steering column (ignition) lock cylinder contact a resistor pellet located in the ignition key. The theft deterrent module measures the resistance of the key pellet. The module compares this value to a value stored in memory. The theft deterrent module then performs one of the following functions:

• | If the values match, the theft deterrent module performs the following system enable functions:

• | The module provides a ground for the theft deterrent relay at terminal A4 (CKT 625, YEL/BLK). The ground enables the starter to operate.

• | The module sends a proper pulse width modulated (PWM) signal to the PCM. The signal travels via CKT 229 (DK BLU), terminal A3. When the PCM receives this input, it enables the fuel delivery system.

• | If the values do not match, the theft deterrent module performs the following system disable functions for approximately three minutes:

• | No ground is provided to the theft deterrent relay. The starter is disabled.

• | No command is given to the PCM in order to enable the fuel delivery system.

If you turn the ignition switch to the RUN position anytime during the system disable interval, the theft deterrent module disregards the key pellet value until the three minute system disable interval is complete. This action occurs even if you use the correct key pellet value.

After approximately three minutes, the theft deterrent module performs the following actions:

• | The module measures the key pellet resistance.

• | The module compares the key pellet resistance to a value stored in memory.

If the values match, the theft deterrent module performs the system enable function. If the values do not match, the module performs the system disable functions again.

If the theft deterrent module is unable to measure the key pellet resistance due to a damaged or missing pellet, the module does not perform the system enable or system disable functions. No three minute interval is performed. A measurable key with the correct resistance value can be used in order to start the vehicle.

### Security Indicator Operation

When you turn the ignition switch to the RUN position, the SECURITY indicator illuminates for approximately five seconds. The indicator notifies the driver that the system operates correctly.

The PASS-Key® II system indicator operates in the following four modes:

• | The indicator illuminates when you turn the ignition switch to RUN (five second bulb check). This shows that the indicator and system operate correctly

• | The indicator illuminates after the engine starts. This indicates that one of the following conditions has occurred:

• | The theft deterrent module is not properly programmed. You may use more than one key code value in order to start the vehicle. The improperly programmed module condition usually occurs on a vehicle where the module has been recently replaced. Refer to Programming Replacement Keys, Ignition Cylinder, or Powertrain Control Module .

• | The theft deterrent module detected a malfunction in the PASS-Key® II system while the engine was running. Verify that the following conditions are met. For further diagnosis, refer to Content Theft Deterrent (CTD) System Check .

• | The theft deterrent module connections are secure.

• | You are using a good ignition key.

• | The indicator illuminates, but the engine does not start. The theft deterrent module has detected an incorrect key pellet resistance key code value. The system disable functions activate. Take the following actions:

1. | Remove the key from the ignition.

2. | Verify that the correct key code (Key pellet) is being used in order to start the vehicle. Use a J 35628-A in order to measure each key pellet for the vehicle. All key codes should match.

3. | Wait for approximately three minutes for the system disable timer to expire. Use a known good key with the correct key code in order to attempt to restart the engine.

4. | If the engine still won't start, refer to Content Theft Deterrent (CTD) System Check .

• | The indicator flashes and the engine does not start. The theft deterrent module has detected an open or short in the ignition key resistor input circuit. During this mode of operation, the theft deterrent module does not start the system disable timer. Refer to Content Theft Deterrent (CTD) System Check .

### Theft Deterrent Module

The theft deterrent module contains the software in order to do the following actions:

• | To monitor the inputs for the PASS-Key® II system

• | To control the outputs for the PASS-Key® II system

The following circuits are the theft deterrent module inputs:

• | The battery voltage (CKT 1642, RED) input to the module draws about 1 milliamp when the ignition is OFF.

• | The ignition voltage (CKT 139, PNK) input (Buick) is used to wake up the module. When you turn the ignition switch to the RUN position, the module continuously measures the ignition key resistor. When the ignition switch is in OFF, LOCK or ACCY, the module does not measure the ignition key resistor.

• | Ground (CKT 251, BLK/WHT)

• | The key resistor (CKT 1073, WHT/BLK) and the key resistor ground (CKT 1074, PPL/WHT) inputs are used to determine if you are using the correct key in order to start the vehicle.

The following circuits are the theft deterrent module outputs:

• | The theft deterrent module (CKT 625, YEL/BLK) output controls the theft deterrent relay.

• | The fuel enable (CKT 229, DK BLU) output commands the PCM in order to enable the fuel delivery. When the theft deterrent module sees the proper ignition key resistance, the module sends a pulse width modulated (PWM) signal to the PCM. If the theft deterrent module does not see the proper ignition key resistance, the module does not send a PWM signal to the PCM.

• | The SECURITY indicator (CKT 264, DK GRN) output controls the indicator that is located within the instrument cluster.

### Theft Deterrent Relay

The theft deterrent relay allows the engine to crank only when CKT 625 (YEL/BLK) is grounded by the theft deterrent module.

### Powertrain Control Module (PCM)

The PCM monitors CKT 229 (DK BLU) in order to determine when to enable the fuel delivery system.

The PCM has some diagnostic features associated with the PASS-Key® II system. Some of the features are the diagnostic trouble codes. Refer to Powertrain On Board Diagnostic (OBD) System Check in Engine Controls.