What can I do to cut cost on a starter generator control module ?

The cost to replace the transmission control module (TCM) on a 2003 Audi A4 can vary depending on several factors, such as the location of the repair shop, the extent of the damage to the TCM, and the cost of the replacement part.
On average, the cost of replacing the TCM for a 2003 Audi A4 can range from $500 to $1,500. This cost includes the cost of the replacement part and the labor involved in the repair. However, depending on the extent of the damage to the TCM or if other parts need to be replaced along with the TCM, the cost can go up significantly.
It's always a good idea to get a quote from a reputable repair shop before proceeding with any repairs. They can provide you with a more accurate estimate based on the specific details of your situation. Additionally, if your Audi A4 is still under warranty, the cost of the repair may be covered, so it's worth checking with your dealer to see if this is the case.

U can't , software programmed into the computers . You would need to have computer re manufacturer delete pats an reprogram PCM - IPC - which ever control modules control the anti-theft system . Because if the PCM - engine computer does not see a coded message from the PATS module IPC - instrument cluster etc.. it won't engage the starter an or fuel injectors . It would cost less to have it fixed right by a qualified repair shop. or mobile lock smith .

There is no direct connection from the purple wire to the ignition switch . This is computer controlled , Ignition switch is a low voltage input to the BCM - body control module . When you turn the key to start the BCM see's this an sends a message on the serial data network to the PCM / ECM - engine computer . IF the PCM / ECM see's voltage from the Internal mode switch in the transmission it knows it is in park or neutral an see's no problems with the anti- theft system it will energize the crank relay sending Battery voltage on the purple wire to the starter solenoid . You have no clue of the complexity of this system , do yourself a favor an take it to a qualified repair shop . Before you make matters worse . You already spent money on a new starter needlessly .

Circuit Description
Moving the ignition switch to the START position signals the body control module (BCM) through discrete inputs from the ignition transducer that engine crank has been requested. The BCM verifies that theft is not active and sends a serial data message to the engine control module (ECM)/powertrain control module (PCM) requesting engine start. The ECM/PCM receives a 12-volt signal from the park/neutral position (PNP) switch or clutch pedal start switch notifying that it is safe to start the engine. There is a splice on this circuit in the fuse block-underhood that supplies power for the starter relay coil. The starter relay coil control circuit is then grounded by the ECM/PCM closing the switch in the starter relay suppling 12 volts to the S-terminal of the starter. Ground is supplied through the engine block.
Vehicle Theft Deterrent (VTD) Description and Operation
Circuit Description
The Passlock?"¢ system is provided in order to prevent vehicle theft if the ignition lock cylinder is forced to rotate. The Passlock controller reads the coded Passlock?"¢ data signal. The data consists of a voltage generated by a voltage divider network created between the Passlock assembly and the Passlock?"¢ controller. If the data is correct , indicating rotation of the lock cylinder with the proper mechanically cut key, then the Passlock?"¢ controller sends a password to the Powertrain controller over the class 2 bus to indicate that starter engagement should be allowed. The Passlock?"¢ controller also interfaces with the driver displays subsystem to indicate, via a Security telltale, the Passlock?"¢ subsystem's status and acute subsystem failures.
The components of the Passlock?"¢ System are as follows:
?€¢
The ignition switch

?€¢
The body control module (BCM)

?€¢
The security indicator on the instrument cluster

?€¢
The engine control module (ECM)

Who makes a TK. Remember we are a USA website.

Test the electrical circuit's . View wiring diagrams to see what all is involved in the starter circuit's , park neutral safety switch , starter relay , engine computer / PCM / ECM etc..... Depends on make , model an year vehicle . On some vehicles the ignition switch is a input to a control module (BCM-PCM ) the one control module sends a message over a computer data network to another control module which energizes the starter relay sending B+ voltage to the S terminal on the starter solenoid . Your best bet , have it towed to a qualified repair shop.

Has no starter relay , starter controlled by TIPM - totally integrated power module . The TIPM is a fuse box / control module . Suggest you have it towed to the dealer , Recall on the TIPM .
Defective TIPM Is Causing Dangerous Power Problems in Chrysler Vehicles

could be a starter solenoid, or motor, or starter relay problem, or signal wire to starter is loose, could be anything, around the stertar control.

The alternator is not charging the battery back up.

Do you have a key that has a black chip at the base of it? if you do, you have a vats problem. VATS...Vehicle Anti-Theft System. this would explain
the security light. the way the system works is that the chip (or pellet) in the key has a certain resistance
value,when you put the key in the ignition the keyswitch sends a signal to the vats module wich verifies the resistance and sends a signal to the cars computer that turns on the signal for the fuel injectors and enables the starter.
without this the car thinks its being stolen and disables the injectors after 3 seconds or so,and also
will disable the starter. so heres the souloution.
only three things can be wrong with this system
1. your keys is bad.
2.your keyswitch is bad
3.your vats module is bad
the pellet on the key will sometimes get worn out
after many years of use and will not make contact within the keyswitch. If you have a spare newer key try to see if this cures it. It cost about 27.00 for a new key. all prices quoted are for parts only. I am a mech so I do everything myself.

as I mentioned before the keyswitch may be worn on the inside and not making contact or 1 or 2 of the wires inside may be broken. very common for this to happen. new keyswitch cost arround 30.00 but you have to get a new key cut

your vats module may be bad. when this happens replacement may be your only recourse. they usualy cost about 300.00 if you can find them. very easy to replace. plug and play. the only trouble is getting to it as its located behind the glove compartment along with the anti theft relay. Also GM stopped making this part early last year so supplies are limited

my best sugestion to you is to buy a vats bypass module. its about 20.00 and you wire it into the harness you unplugged from your vats module. I just did one today on my sons car. had the same problem as yours. heres the link wheres you can get one.
www.xdponline.com I have no association with them other than thats where I got mine.(through there e-bay store) takes about 30 min to install..start to finish
heres another useful linkthat will help you install this
item
http://newrockies.ca/if-your-car-has-a-TDM/

I do not know anywhere that can repair the module, and yes one from a salvage yard is a good idea.