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EMRSR, Master Certified Service Manager
Category: Ford
Satisfied Customers: 3010
Experience:  20 years with Ford, Master Certified
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1998 Mercury Grand Marquis: parked..all the fuses and relays..keys

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I own a 1998 Mercury Grand Marquis and last friday my car failed to start after standing only a few minutes parked. I checked all the fuses and relays then noticed the pats light on the dash was no longer working. I even tried the original keys that came with the car. Still no sucsess. So I had the car towed home to check other things. At no time has the led illuminated. Charged the battery fully rechecked fuses 4, 7 and 8 again found all good. Car cranks fast but no start. The car drove fine before this happened. The car has 55K miles on it and never had any problems before.I have power to the pats tranponder by the key with ignition on but no led present. Is there any way to bypass this pats feature? I dont want to spend more than the car is worth to get this fixed. I'm lost!!! I also noticed no fuel pressur at the fuel rail at ant time and checked the inertia switch in the trunk fir continuity.
Submitted: 6 years ago.
Category: Ford
Expert:  EMRSR replied 6 years ago.

All elements and components of the PATS System must be functional or the vehicle will not start. This includes the PCM and PATS Module communications. There is no bypassing, the system has even got more complicated as the years have passed.


Section 13-11: Anti-Theft System, Passive1998 Crown Victoria/Grand Marquis Workshop Manual
DESCRIPTION AND OPERATIONProcedure revision date: 03/16/1998


Anti-Theft System, Passive


The passive anti-theft system has been significantly upgraded from the prior model year.

The passive anti-theft system (PATS) uses radio frequency identification technology to deter a driveaway theft. Passive means that it does not require any activity from the user. This system is known as SecuriLock® in North America, Safeguard® in the U.K., and PATS in continental Europe. This information can be found in customer literature such as the owner's manual.

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 service 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 powertrain control module (PCM) to enable or disable the engine. The PATS module communicates with the PCM over the J1850 standard corporate protocol (SCP) network in order to enable engine operation. The PATS module and the PCM use sophisticated messages in order to deter a theft. PATS and the PCM share security data when first installed together that makes them a matched pair. After this security data sharing, these modules will not function in other vehicles. The PCM 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 service procedures outlined in the workshop manual that may be performed 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 properly, 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 for more than three seconds when the ignition switch is turned to RUN or START. PATS also flashes the theft indicator lamp every two seconds at ignition OFF to act as a visual theft deterrent.

PATS differs from the perimeter anti-theft system in that the 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.

Customer: replied 6 years ago.
So your saying that I'm screwed? Have you ever seen any other problems causing the led not to illuminate? Besides a blown fuse?
Expert:  EMRSR replied 6 years ago.

For the few that I have seen fail it has been the PATS Module, these are few and far between. We service 10-12k cars a year and this is not the norm for that system.

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