FiatPrecoding

Fiat Transponder precoding

Each Fiat model has a 5 digit pincode. In order to program keys into a Fiat you must know what this pincode is. The HT2 software will read it directly from the vehicle for you. 

Before any transponder can be programmed into a bladed key Fiat system, it must be ‘precoded’. You can think of this as personalising the key for that unique vehicle that you are working on. No other vehicle will have this same ‘precoding’. If you order a key from the dealership, it will arrive ‘precoded’. You can simply just program it in. The HT2 software will read this precoding directly from the vehicle. 

The transponder type that this range of Fiat models uses is the HITAG2 transponder from NXP. It can be in the form of a standalone, encapsulated, device (Fig.1) or it can be a PCB mounted device (Fig.2), incorporating some additional circuitry from remote control functions. Each type must be precoded before it can be programmed into the vehicle.

Fig.1 PCF7936

Fig.2 PCF7946

The simplest way to precode these keys is to use a dedicated transponder manipulation device. The TMPro2, Miraclone, Tango, Abrites TAG, AD900Pro are some examples of the devices available which make this process very easy and accomplished in just a couple of seconds. They all require a .bin file. The precoding information is stored within this .bin file. This is the recommended way to precode keys. The HT2 software will automatically read and save this file for you.

Some customers may not have the above equipment and wish to precode the transponders themselves. The HT2 displays this information for you . Precoding manually is much more time consuming and can be prone to errors and due to poor quality of components and design of some of the transponder reading devices, may take many times to read/write to the transponder device. We do not recommend that you do this manually. That said, here follow instructions for using inxepensive HITAG2 programming devices to achieve the precoding manually. Many types of these devices exist, of varying quality and efficacy. No guarantee of their success is implied and the following exists for information only.

HITAG2 PC Software

You must connect the transponder reading device to the PC in order to run the supplied software. Only with this PC software can you manipulate the data within the transponder. You cannot manipulate the data directly from the device itself. 

When connected you will be presented with something like the following:

Place the transponder within the reading range of the device. Then Press ‘Auto Detect’. You should see that the device selects PCF7936. The PCF7936/PCF7946 have 8 ‘pages’ of information, zero through to seven. (referred to in the HT2 information display as P0,P1,P2,P3,P4 RSK LOW, P5 RSK HIGH, P6 RCF, P7 NOT SHOWN).

Click ‘Read All Pages’. This will take a little time and then you will see Pages 0 through 7 are populated with information. 

Page0: 

Each transponder has a unique, 4 bytes long identifier (IDE). This is set at the factory and cannot be altered. In the example in Fig.2 the IDE of this particular transponder is 34 85 8C 1C. YOU CANNOT AND DO NOT NEED TO ALTER ANYTHING HERE

Page 1: 

This contains the first part of the precoding information which must be altered. Currently, it is set to the factory default. The factory default value is 4D 49 4B 52.

After connecting to the vehicle, the HT2 shows us what the Page1 value needs to be altered to for our vehicle. In this case, we need to alter Page1 to be 65 FC EA C8.

Enter the new P1 values (65 FC EA C8 in this case) into the HITAG2 PC Software and press ‘Write1’ (W1). This will Write page1 only.

We must now change the values in the ‘Factory Config’ section to match our new Page1, or we will no longer be able to alter anything within the transponder.

Page 2: 

This contains the next part of the precoding information which must be altered. Currently, it is set to the factory default. The factory default value is 00 00 4F 4E.

After connecting to the vehicle, the HT2 shows us what the Page2 value needs to be altered to for our vehicle. In this case, we need to alter Page2 to be 00 00 19 3C.

Enter the new P2 values (00 00 19 3C in this case) into the HITAG2 PC Software and press ‘Write2’ (W2). This will Write page2 only.

We must now change the values in the ‘Factory Config’ section to match our new Page2, or we will no longer be able to alter anything within the transponder.

Page 3: 

This contains the next part of the precoding information which must be altered. Currently, it is set to the factory default. The factory default value is 06 AA 48 54.

After connecting to the vehicle, the HT2 shows us what the Page3 value needs to be altered to for our vehicle. In this case, we need to alter Page2 to be 0E AA 48 54.

Enter the new P3 values (0E AA 48 54  in this case) into the HITAG2 PC Software and press ‘Write3’ (W3). This will Write page3 only.

If we are precoding a plain PCF7936 then, as there is no remote capability with this transponder, we are now done precoding our transponder and can proceed to programming it into the vehicle by OBD using the HT2 software.

If we are precoding a PCF7946 remote control key, there are some further steps. 

Page 4 / RSK LOW: 

This contains the next part of the precoding information which must be altered.

After connecting to the vehicle, the HT2 shows us what the Page4/RSK LOW value needs to be altered to for our vehicle. In this case, we need to alter Page4/RSK LOW  to be 68 D7 9A 96.

Enter the new P4/RSK LOW values (68 D7 9A 96  in this case) into the HITAG2 PC Software and press ‘Write4’ (W4). This will Write page4/RSK LOW only.

Note. Some PC Software, when a PCF7946 has been autodetected, will separate P4,P5,P6,P7 into a ‘Remote’ area, as in the above example.

Page 5 / RSK HIGH: 

This contains the next part of the precoding information which must be altered.

After connecting to the vehicle, the HT2 shows us what the Page5/RSK HIGH value needs to be altered to for our vehicle. In this case, we need to alter Page5/RSK HIGH  to be 00 00 7C 6E.

Enter the new P5/RSK HIGH values (00 00 7C 6E in this case) into the HITAG2 PC Software and press ‘Write5’ (W5). This will Write page5/RSK HIGH only.

Page 6 / RCF: 

This contains the final part of the precoding information which must be altered.

We must determine something about the remote key that we are wanting to program. There is a surface mount device (SMD) on the PCB. It can be with either 8 legs, with 10 or with 16.

The SMD referred to is shown above. In this case, it has 10 pins. After connecting to the vehicle, the HT2 shows us what the Page6/RCF value needs to be altered to for our vehicle.

Highlighted is what we must enter if our SMD has either 10 pins or 16 pins (37 1A F2 D5). If the SMD has 8 pins, then that info is also shown (77 1A F2 D5). Failure to set this correctly will result in the remote control not functioning. Now that we have correctly precoded our keys, we can program them to the vehicle by OBD.

Programming keys by OBD:

You will need the pincode for the vehicle. The HT2 will determine and enter this automatically for you. The software will prompt you through the process of programming the keys. Pay attention to the notes below.

IMPORTANT NOTE WHEN PROGRAMMING KEYS BY OBD

All keys, BOTH OLD AND NEW, must be programmed to the vehicle at the same one time. It does not matter which order you insert the keys. You can program the old one as the first and then the new as the second, or vice versa. What does matter, is that you program ALL OF THE KEYS IN THE SAME ONE PROCEDURE. Any keys not programmed are added to an internal list of ‘cancelled keys’. The BCM remembers them and will not allow you to program them subsequently. If the remote buttons do not function, this is a result of either incorrect selection of remote key (some are Delphi/Some Marelli) or incorrect precoding. It is not a problem with the HT2 software. If the key starts the car, then the HT2 software has done its job correctly.