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Questions and Answers

Jeep Cherokee Alarm Disarming

Q. Hi, I found your web site and am very impressed. I have a question regarding a Jeep I just bought. It is a 1997 Jeep Cherokee Limited 4 liter L6 with an automatic transmission. When I unlock it to have it washed, the alarm automatically activates after a couple of minutes and this causes a problem for me as I am living in Gauteng, South Africa, the crime capital of South Africa.

Jeep Cherokee Alarm Disarming

Every time this happens my neighbors go ballistic. I want to disable this auto arming feature if possible can you help?

Thanks,
Deon

A. If you leave the front doors unlocked, the alarm shouldn't arm itself. This is how the Vehicle Theft Security System (VTSS) operates. Probably more than you want to know about it.

INTRODUCTION:
The Vehicle Theft Security System (VTSS) is an available factory-installed option on versions of this model built for sale in North America. This system is designed to provide perimeter protection against unauthorized use or tampering by monitoring the vehicle doors, liftgate, and ignition system. If unauthorized use or tampering is detected, the system responds by sounding the horn, flashing the exterior lamps, and providing an engine no-run feature. The VTSS can be disarmed by unlocking the vehicle with the key in either front door lock cylinder or using the Remote Keyless Entry (RKE) transmitters.

The vehicle immobilizer system is factory-installed standard equipment on models built for sale outside North America. Models equipped with the vehicle immobilizer system cannot be equipped with the VTSS. The vehicle immobilizer system is designed to provide passive protection against unauthorized vehicle use by preventing the engine from operating while the system is armed. The vehicle immobilizer system can only be disarmed using the Remote Key-less Entry (RKE) transmitters.

Following are some general descriptions of the features of the VTSS and the vehicle immobilizer system. Refer to Power Lock Systems for more information on the RKE system receiver and transmitters. Refer to Vehicle Theft Security System for complete circuit descriptions and diagrams.

NOTE: This information covers both Left-Hand Drive (LHD) and Right-Hand Drive (RHD) versions of this model. Whenever required and feasible, the RHD versions of affected vehicle components have been constructed as mirror-image of the LHD versions. While most of the illustrations used represent only the LHD version, the diagnostic and service procedures outlined can generally be applied to either version. Exceptions to this rule have been clearly identified as LHD or RHD, if a special illustration or procedure is required.

ENABLING

Vehicle Theft Security System:
The VTSS engine no-run feature is disabled when it is shipped from the factory. This is done by programming within the Powertrain Control Module (PCM) . The logic in the PCM prevents the VTSS engine no-run feature from arming until the engine start counter within the PCM sees twenty engine starts. The VTSS no-run feature must be enabled when the vehicle is received from the assembly plant.

The preferred method for enabling the VTSS engine no-run feature is to electronically advance the PCM engine start counter using a DRB scan tool. Refer to the Vehicle Theft Security System menu item on the DRB scan tool for the procedures. Once this condition has been met, the PCM will allow the engine no-run feature to arm.

Once the VTSS engine no-run feature has been enabled, it cannot be disabled unless the PCM is replaced with a new unit. The same VTSS engine no-run feature enable logic will apply anytime the PCM is replaced with a new unit.

Vehicle Immobilizer System:
The vehicle immobilizer system is disabled when it is shipped from the factory. This is done by programming within the Powertrain Control Module (PCM) and the Body Control Module (BCM) . The logic in the BCM allows the vehicle immobilizer system functions to remain dormant in vehicles sold in countries where it is not required. The logic in the PCM prevents the immobilizer system from arming until the engine start counter within the PCM sees twenty engine starts. The vehicle immobilizer system must be enabled when the vehicle is received from the assembly plant, if this feature is required or desired.

Once the vehicle immobilizer system has been enabled, it cannot be disabled unless the PCM and the BCM are replaced with new units. The same vehicle immobilizer system enable logic will apply anytime the PCM and/or the BCM are replaced with new units.

ARMING

Vehicle Theft Security System:
Passive arming of the VTSS occurs when the vehicle is exited with the key removed from the ignition switch, the headlamps are turned off, and the doors are locked using the power lock switch. The power lock switch will not function if the key is in the ignition switch or the headlamps are on with the driver side front door open. The VTSS will not arm if either front door or the liftgate are locked using the key in the lock cylinder.

Active arming of the VTSS occurs when the Remote Keyless Entry (RKE) transmitter is used to lock the vehicle, even if the doors and/or the liftgate are open when the RKE transmitter Lock button is depressed. However, the VTSS arming will not be complete until all the doors and the liftgate are closed.

Following successful passive or active VTSS arming, the VTSS set lamp on the top of the instrument panel will flash rapidly for about fifteen seconds after the illuminated entry system times out. This indicates that VTSS arming is in progress. Once the fifteen second arming function is complete, the set lamp will flash at a slower rate to indicate that the VTSS is armed.

Vehicle Immobilizer System:
Active arming of the vehicle immobilizer system occurs when the vehicle is locked using the power lock switch or when the Lock button of the Remote Keyless Entry (RKE) transmitter is used to lock the vehicle. Arming will occur, even if the doors and/or the liftgate are open when the vehicle is locked, as long as the ignition switch is in the Off position. The vehicle immobilizer system cannot be actively armed while the ignition switch is in the On or Start positions.

Passive arming of the system occurs when the ignition switch is in the Off position for more than five minutes (one minute for vehicles sold in the United Kingdom). See Power-Up Mode for a description of other conditions that can result in passive arming of the vehicle immobilizer system.

Following receipt of a passive or active request for arming of the vehicle immobilizer system, a set lamp located on top of the instrument panel will begin to flash rapidly for fifteen seconds . Following successful vehicle immobilizer system arming (about fifteen seconds ), the set lamp will continue to flash, but at a much slower rate. The slow flashing of the set lamp will continue for as long as the vehicle immobilizer system is armed.

DISARMING

Vehicle Theft Security System Passive disarming of the VTSS occurs when the vehicle is unlocked using the key to unlock either front door or the liftgate. Active disarming of the VTSS occurs when the vehicle is unlocked by depressing the Unlock button of the Remote Keyless Entry (RKE) transmitter.

Once the alarm has been activated (horn sounding, lights flashing, and the engine no-run feature), either disarming method will also deactivate the alarm.

Depressing the Panic button on the RKE transmitter will also disarm the VTSS, but the horn will sound and the lights will flash for about three minutes as part of the Panic feature. Refer to Power Lock Systems for more information on the Panic feature.

Vehicle Immobilizer System:
Active disarming of the vehicle immobilizer system occurs when the Unlock button of either of the two Remote Keyless Entry (RKE) transmitters is depressed, regardless of ignition switch position. This is the only way that the vehicle immobilizer system can be disarmed. Following successful disarming of the vehicle immobilizer system, the set lamp on top of the instrument panel will stop flashing.

POWER-UP MODE

Vehicle Theft Security System:
When the armed VTSS senses that the battery has been disconnected and reconnected, it enters its power-up mode. In the power-up mode the alarm system remains armed following a battery failure or disconnect. If the VTSS was armed prior to a battery disconnect or failure, the system will have to be actively or passively disarmed after the battery is reconnected.

The power-up mode will also apply if the battery goes dead while the system is armed, and battery jump-starting is attempted. The engine no-run feature will prevent the engine from starting until the alarm system has been actively or passively disarmed.

Vehicle Immobilizer System:
When the vehicle immobilizer system senses that the vehicle battery has been disconnected and reconnected, it enters its power-up mode. If the immobilizer system was armed prior to the battery disconnect, the system remains armed when the battery is reconnected.

If the immobilizer system was disarmed prior to the battery disconnect, the system will remain disarmed if the battery is reconnected within five minutes (one minute for vehicles sold in the United Kingdom). The system will passively arm itself when the battery is reconnected more than five minutes (one minute for vehicles sold in the United Kingdom) after a battery disconnect or failure. After any passive arming, the system will have to be actively disarmed by depressing the Unlock button on one of the Remote Keyless Entry (RKE) transmitters.

The power-up mode logic also applies if the battery goes dead, and battery jump-starting is attempted. The engine no-run feature will prevent the engine from operating until the vehicle immobilizer system has been actively disarmed.

TAMPER ALERT:
The VTSS tamper alert will sound the horn three times upon disarming, if the alarm was activated and has since timed-out (about eighteen minutes ). This feature alerts the driver that the VTSS was activated while the vehicle was unattended.

CIRCUIT OPERATION:
Each door, the liftgate, hood, and the liftglass in the liftgate have an ajar switch that connects to the Body Control Module (BCM) . The ajar switches are normally open when the doors, liftgate, liftglass and hood are closed. When one of them open, its ajar switch closes and connects the BCM to ground. In response, if the Vehicle Theft Security System is armed, the BCM starts the alarm. Refer to the Introduction in this section for alarm information.

The BCM receives the ajar switch signals on the following circuits.

  • Circuit G75 provides left front door ajar switch signal
  • Circuit G74 provides right front door ajar switch signal
  • Circuit G77 provides left rear door ajar switch signal
  • Circuit G76 provides right rear door ajar switch signal
  • Circuit G78 provides liftgate ajar and liftglass ajar signals.

Additional Information provided courtesy of AllDATA

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© 2005 Vincent T. Ciulla

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