You are not logged in! This article is in Preview mode!

Click Secure Login to login and view this article in its entirety.

If you are not a member please feel free to preview this article.
However please note that much of the content will be unavailable including some images;

Ford PATS

P.A.T.S. stands for Passive Anti-Theft System. It is called passive because it requires no action on the part of the driver. Ford likes to play an annoying little game of PATS hide-and-go-seek. That is to say, they cant seem to decide where they want to put the PATS system. Not only do they play hide and seek with it, they keep changing how it operates. There are five different PATS systems, you will need to review technical information specific to the vehicle you are servicing prior to beginning any diagnostic work on a PATS system.

The Key

The PATS system uses a key that contains a tiny electronic device called a transponder located inside the handle. The transponder emits a radio frequency code that is read by the PCM or the PATS module (system-type dependent).

The key is electronic, but requires no batteries. It is powered by a Radio Frequency (RF) field surrounding the opening of the ignition key cylinder. This RF field is created by the transceiver that is located at the open end of the cylinder just beneath the column shrouding. The RF frequencies are picked up by a tiny coil located in the transponder that serves as an antenna. The coil then transfers that energy into a tiny capacitor as an electrical charge. The newly charged capacitor serves as a battery to temporarily power the transponder's logic circuitry. Once powered up, the logic circuitry then returns its coded message back through the coil. The coil once again serves as an antenna, but only this time it is sending instead of receiving. The coil emits its coded message out of the head of the key via radio waves to be picked up by the transceiver.

The Transceiver

The duties of the transceiver are to supply power to the transponder in the key head, receive the transponder's coded message, and then to send that encoded message to the PATS module or PCM via hard wiring. The transceiver may communicate with the key twice, depending on the system type. The first reading comes as soon as the key-in sense switch has been tripped. The second comes when the cylinder is switched to the on position. For systems where the PCM performs all of the PATS functions, there will only be one code reading. That reading will take place at the key-on position as soon as the PCM wakes up. On a system that contains the PATS module in the cluster, the cluster will have woken up as soon as the door handle was lifted to enter the vehicle. The cluster will be ready to receive the code reading long before the key-in sense switch is tripped by the driver.

The transceiver module is a slave to the PATS module. The transceiver makes no decisions. Even when to read the key code is a decision that is not in the hands of the transceiver.

The transceiver is located at the open end of the cylinder just beneath the column shrouding. It is secured by one screw, usually a T-20 non-security style Torx. The body of the transceiver is square with a loop that extends from the side of it to surround the opening of the ignition key cylinder.

The PATS Module

The PATS module can be a standalone module, it can be integrated into the instrument cluster, or all functions of the PATS can be contained inside the PCM, depending on year and model.

The duties of the PATS module are to:

1. Initiate the key read.

2. Store the key codes in non-volatile memory.

3. Compare the user's key code against the stored key codes.

4. Sending 'OK to start' and 'do not start messages' to the PCM via the SCP network ...

You are not logged in! This article is in Preview mode!

Click the "Secure Login " link in the upper right to login and view this article in its entirety.