Passlock
The passlock system is a vehicle theft deterrent system which deters drive-away
vehicle theft by disabling engine operation if the ignition lock cylinder is not
rotated with the proper mechanically cut key.
The passlock system is made up of an ignition switch assembly, passlock sensor,
body control module (BCM), instrument panel cluster (IPC), and a powertrain control
module (PCM).
The ignition switch contains a magnet mounted on the lock cylinder and a passlock
sensor assembly which consists of security hall effect sensor, tamper hall effect
sensor, and output resistors. A drill proof metal shield is also staked over the
sensor housing.
The passlock sensor mounted to the ignition switch assembly is located inside
the upper right side of the steering column. The passlock sensor contains two hall
effect sensors: a tamper hall effect sensor and a security hall effect sensor. The
tamper hall effect sensor is mounted on top of the security hall effect sensor. Should
someone attempt to defeat the system by use of magnetic experimentation, the tamper
hall effect sensor will activate first.
The BCM has the passlock controller integrated into it which controls the majority
of the security systems logic. The BCM reads the data from the passlock sensor continuously.
If the data is correct and has been received by the BCM within a specified time,
the BCM will send a coded password to the PCM. The PCM will then allow the fuel injectors
to operate.
The coded password for the security system is sent from the body control module
to the PCM via the class 2 data link. If the password is correct and received
within the specified time, the PCM will allow the fuel injectors to operate.
The IPC contains the security telltale. The security telltale has three modes
of operation, OFF, FLASHING, and ON.
SECURITY TELLTALE will be off if:
| • | Ignition is in the OFF position |
| • | Ignition is in the RUN, START, or ACC position and security system diagnostics
have all PASSED |
SECURITY TELLTALE will be on if:
| • | The BCM is performing a bulb check at vehicle start |
| • | Security system diagnostics have not yet completed at vehicle start |
| • | A security system diagnostic trouble code (DTC) is set in the BCM or PCM |
SECURITY TELLTALE will be flashing if:
| • | The tamper hall effect sensor has been triggered |
| • | Incorrect passlock sensor data to BCM for more than 5 seconds during
vehicle start |
| • | No passlock sensor data to the BCM for more than 5 seconds during
vehicle start |
| • | Incorrect password from the BCM to the PCM after 5 seconds during
vehicle start |
System Operation
The passlock system is designed to prevent vehicle operation if the mechanical
key is not used to start the vehicle. The mechanical key, in normal operation, will
turn the passlock lock cylinder. The passlock sensor (which is mounted to the passlock
lock cylinder assembly) sends data by circuit 1836 to the body control module (BCM).
The passlock sensor is powered by circuit 1459 from the BCM. The passlock sensor
is grounded by circuit 1835 to the BCM. The BCM determines the validity of the passlock
sensor data within a preset time window based on ignition switch input. The BCM will
then send a coded password to the PCM by class II, circuit 1807. When the PCM receives
the correct code, it will allow the fuel injectors to operate normally.
PASSLOCK MODES
| | The pass theft mode is normal operation. During a normal start up, the SECURITY
telltale will turn on. The telltale will turn off when: |
| - | the ignition is turned to the OFF or ACC position. |
| - | when the ignition is turned to the START position and a 3 second
timer has expired. |
| • | Short Tamper Mode (Fuel Disabled Timer Mode) |
| | The powertrain control module (PCM) enters the short tamper mode if the BCM
detects an open voltage code (4.43v-5.00v). The BCM will send out the fuel undecided
password to the PCM. The PCM will disable fuel supply to the engine for 4 seconds. |
| | The driver usually observes a start quickly followed by a stall when in the
short tamper mode. After 4 seconds a start may again be attempted, except
in one situation. |
| | If the PCM receives the wrong password (example: a new BCM was installed without
following the relearn procedure - the SECURITY telltale will flash for 4 seconds
and remain on, and the fuel injectors will remain disabled until correct relearn
procedure has been completed. |
| | The body control module (BCM) enters the long tamper mode if the BCM receives
the wrong voltage code at an attempted start. The BCM will then send a disable fuel
message to the PCM. The PCM will then disable the fuel injectors. |
| | The driver experiences the same start quickly followed by stall. The fuel will
be disabled for 10 minutes and the SECURITY telltale will also flash. |
| | In the fail enable mode, the engine is allowed to run normally because the fault
occurred while the engine was running. The SECURITY telltale will remain on
whenever the engine is running to alert the driver there is a problem with the passlock
system and there is no passlock system protection. The engine can be restarted in
the fail enable mode. |
| | Whenever the engine is running, the passlock system constantly monitors itself.
The BCM monitors the circuits between itself and the passlock sensor. The BCM and
PCM also monitor each other through the serial data link. If a problem is detected,
diagnostic trouble code(s) will be set and the SECURITY telltale will be On when
the engine is running. |
DIAGNOSTIC TROUBLE CODES
In either the short or long tamper mode, the BCM or the PCM will set diagnostic
trouble code(s). Each module should be checked for codes (both current and history).
