Question about 2001 Mercury Mountaineer
Keypat not working
Posted on Sep 26, 2012
The passive anti-theft system (PATS) contains the following components:
The PATS uses a specially-encoded ignition key. Each encoded ignition key contains a permanently installed electronic device called a transponder. Each transponder contains a unique electronic identification code out of over 72 million billion combinations.
Each encoded ignition key must be programmed into a vehicle's PATS module before it can be used to start the engine. There are special diagnostic repair procedures outlined in this manual that must be performed if the encoded ignition keys need to be replaced.
The encoded key is larger than a traditional ignition key. The key does not require batteries and should last the life of the vehicle.
The transceiver module communicates with the encoded ignition key. This module is located behind the steering column shroud, and contains an antenna connected to a small electronics module. During each vehicle start sequence, the transceiver module reads the encoded ignition key identification code and sends the data to the PATS module.
The control functions are contained in the PATS module. This module performs all of the PATS functions such as receiving the identification code from the encoded ignition key and controlling engine enable. The PATS module initiates the key interrogation sequence when the vehicle ignition switch is turned to RUN or START.
PATS uses the p owertrain control module (PCM) to enable or disable the engine. The PATS module communicates with the PCM over the SCP communication network in order to enable engine operation. The PATS module and the PCM use sophisticated messages in order to prevent a theft. The PATS and the PCM share security data when first installed together, making them a matched pair. After this security data sharing, these modules will not function in other vehicles. The PCM shared security ID is remembered even if the battery is disconnected. The PATS module also stores the vehicle's key identification code, even if the battery is disconnected. There are special diagnostic repair procedures outlined in this workshop manual that may be carried out if either the PATS module or the PCM needs replacement.
All the elements of PATS must be functional before the engine is allowed to start. If any of the components are not working correctly, the vehicle will not start.
PATS uses a visual theft indicator. This indicator will prove out for three seconds when the ignition switch is turned to RUN or START under normal operation. If there is a PATS problem, this indicator will either flash rapidly or glow steadily when the ignition switch is turned to RUN or START. PATS also "blips" the theft indicator every two seconds at ignition OFF to act as a visual theft deterrent.
PATS differs from the perimeter anti-theft system in that PATS enables and disables the engine from starting. If equipped, the perimeter anti-theft system protects the perimeter of the vehicle (doors, hood and trunk) and sounds an alarm.
The PATS is not compatible with aftermarket remote start systems, which allow the vehicle to be started from outside the vehicle. These systems may reduce the vehicle security level, and also may cause no-start issues. Remote start systems must be removed before investigation of PATS-related No Start issues.
The passive vehicle protection system will be activated and will disable the vehicle from starting if there is a:
Posted on Nov 10, 2010
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Posted on Jan 02, 2017
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