Electrical problem
1999 Volkswagen Jetta 6 cyl Front Wheel Drive Manual 180000 miles

I am going to replace the headlights. This will require me to remove the battery. Once Idisconnect it, I am concerned about the need to reset the computer - I have had problems in the past and had to tow the car 50 miles to a dealer to reset.

Question 1: will I have to reset the computer and

2: if I do how is it done.

Hello, I hate to say but it does look like according to battery removal/installation the ECM does need to be reset. I have include the battery removal/installation and down in the notes it states; “For OBD II vehicles, the readiness code for the Engine Control Module (ECM) must be re-generated after the battery has been disconnected”. I also include coding the ECM and it shows you need special tool,;” VAG1551 Scan Tool (ST) with VAG1551/3 adapter cable.” If it were me, I would attach a battery jump starter to the battery cables and that way you always have battery power to the car even when you disconnect the cables from the car battery and remove it. Obviously we can’t be responsible for things happening as you must remember there is still battery power to the car you are working on. Next, you must make sure the cables do not touch anything that would cause them to short out. Wrap them with rags or something. The big thing is be safe and don’t short something out. I did change a battery that way to prevent dropping the radio codes. It is up to you. Also, not sure why you are changing the headlights but if it is because they are getting delaminated there are kits you can purchase to buff them out. Good luck and be safe.

Removing
•Switch ignition off.
•Open cover -1- for battery case and unhook.
•First disconnect negative GND terminal (arrow) from battery negative (-) pole.
•Disconnect positive B+ terminal from battery positive (+) pole.
CAUTION: Never disconnect or connect the positive B+ terminal from battery while the negative GND terminal is connected Danger of short circuit!
•Flip fuse holder -3- upward.
•Remove fastening bolt -1- from battery case and remove battery case together with heat protection jacket.
•Remove (M8 X 25) hex bolt -3-.
•Remove clamping bracket.
•Remove battery.

Installing
To guarantee the battery seats securely only install batteries with a 10.5 mm battery foot strip and adhere to the following procedures:

Install battery so lug of battery carrier (arrow) engages in battery foot strip cut-out -1-. It must not be possible to move a battery to the left or to the right.
•The battery is correctly installed when the center cut-out in the battery foot strip aligns with threaded hole in the battery carrier (arrows).
•On batteries with hose for central venting, ensure hose is not kinked. Only then can battery vent freely.
•On batteries without hose for central venting, ensure opening on upper side of battery cover is not blocked.
•Install clamping bracket and tighten securing bolt -3- (M8 x 25) to 22 Nm (16 ft. lb ).
•Re-install battery case -2- together with heat protection jacket.
•Fasten battery case with securing bolt -1-.
•Secure (+) positive terminal clamp -2- to positive terminal on battery.
NOTES:
•The battery terminal clamps may only be secured by hand without force in order to prevent damage to the battery housing.
•Battery terminals may no longer be greased.
•Tighten battery terminal clamp securing screw to 6 Nm (53 in.lb ).
Only after the plus terminal securing clamp and the fuse holder have been installed may the Ground (GND) strap be secured to the negative terminal.
•Tighten terminal clamp securing screw to 6 Nm (53 in.lb ).
NOTES:
•When the battery has been reconnected, check operation of electrical equipment (radio, clock and convenience electrics etc.).
•For OBD II vehicles, the readiness code for the Engine Control Module (ECM) must be re-generated after the battery has been disconnected.
•After installing, check if battery is seated securely. The following dangers exist with a loosely installed battery:
•Shortened service life due to damage from vibration.
•The cells in the battery will be damaged if the battery is not secured correctly.
•Damage to battery housing by clamping bracket (possibility of acid leaking, therefore subsequent higher costs).
•Poor crash safety
Batteries with central gas venting
There are two types of batteries with central gas vents:
•Batteries with a hose on central gas vent.
•Batteries without a hose on central gas vent.
It is absolutely necessary to use original sealing plugs in the battery screwed openings to guarantee the battery is sealed correctly.

Use original sealing plugs of same construction if lost or damaged.

The sealing plugs must be installed with an O-ring.

Functional notes for central venting:
•Batteries of the latest generation are equipped with a central venting system with anti-flash protection.
•The anti-flash protection consists of a small round fiberglass mat with a diameter of approx. 15 mm and a thickness of 2 mm . It functions similar to a valve to allow the gasses that form in the battery to vent.
•The gasses that form while charging can vent centrally through an opening on the upper side of the cover The anti-flash protection is also installed at this point, which prevents ignition of the flammable gasses in the battery.


Engine Control Module (ECM), Coding

NOTE:
•A 5-character code must always be displayed during the control module identification.
•The control module must be recorded if the vehicle relevant coding is not displayed or the control module has been replaced.
Special tools and equipment
VAG1551 Scan Tool (ST) with VAG1551/3 adapter cable

Test sequence
•Connect VAG1551 (VAG1552) Scan Tool (ST).
•Switch ignition on and press buttons -0- and - 1- to insert "Engine Electronics" address word 01.
Indicated on display
Rapid data transfer
Select function XX HELP
•Press buttons -0- and -7- to select "Code control module " function 07 and press -Q- button to confirm input.
Indicated on display
Code control module
Enter code number XXXXX (32000)
•Enter relevant code number for vehicle and press -Q- button to confirm input.
Coding variants:
Coding Vehicle
00031 Manual Transmission
00033 Automatic Transmission
The control module identification and coding are indicated on the display, (example)
0219060186 MOTRONIC ME7.1G V06 ->
Coding 00000 WSC 00000
Indicated on display when a non-authorized code number has been entered
Function is unknown or
cannot be carried out at the moment . ->
•Press -> button.
•Press buttons -0- and -6- to select "End Output" function 06 and press -Q- button to confirm input.
•Switch ignition off.
•Check DTC memory. If necessary, repair any malfunctions and erase DTC memory.
•Display readiness code.
If DTC memory has been erased or the Engine Control Module (ECM) was disconnected from permanent battery (B+) voltage, the readiness code must be generated again.

NOTE:
The code entered and shown on the display will not be used by the Motronic control module until the ignition has been switched off once. An incorrect coding leads to:
•Engine running malfunctions (rough gear changes, load change jerks, etc.).
•Increased fuel consumption.
•Increased exhaust gas emissions.
•Malfunctions stored in DTC memory which are not actually present.
•Functions will not be performed (Oxygen Sensor (O2S) control, activation of the EVAP system, etc.).
•On front wheel drive vehicles the traction control will not function (TC warning lamp comes on).
•Reduced Transmission life.