Resolving Interior Lighting \ Alarm\ Immobilizer Problems or Faults

 In a 993 the interior dome lights, the glove box light, the frunk light, and their fixtures and switches are all related to the Alarm and Immobilizer so any bad behavior of any of these components can result in:

• The LEDs on the door sills flash in couplets indicating an Alarm/Immobilizer fault;
• The flashing of the fob light in the clock indicates an immobilize fault;
• The interior cabin dome and frunk light do not go out when the doors and frunk are closed and locked with the fob;
• Additionally, the glove box and frunk stop illuminating when they should;
• The Engine compartment light stays illuminated or will not illuminate;
• The battery is discharged due to a parasitic load due to one of the above reasons.
• If you are only experiencing the inability to program fobs and all other aspects of the interior lighting and immobilizer/alarm are functioning properly look to the bottom of this page for things that will interfere with completing the programming process.

99% of the time any of the above faults can be sorted out by replacing a bulb or fuse or cleaning a lamp socket or switch. Here is a sequence of events to sort out such issues before bringing one's car to a professional for resolution.

Before beginning the below testing procedure remove any LED bulbs and replace them with the originally specified incandescent bulbs used in the interior of the car, the glove box, the frunk, the engine compartment, and the related warning lamps in the clock. 

Also, since we are not the engineers who originally designed these systems the below procedure steps and sequencing is based on making assumptions about the operation of the systems involved from our and others' observations clearing issues and some of these assumptions may be in error.

• Checking the engine compartment lamp function (alarm/immobilizer related):


• If the engine compartment lamp simply won't go out when the latch is closed it can be a stuck lower latch switch from dried grease. Flood the lower latch with CRC QD Electronic Cleaner, or other "electronics" cleaner spray while cycling the latch several times using a screwdriver to set the latch and pulling the release lever on the latch to open the latch.  If the issue is resolved lightly grease the capture mechanism with a very small amount of white lithium grease, release the latch and close the engine lid.
• Do not use something called electric motor cleaner as it may attack the plastic parts in the latch switch.
• If the lamp simply won't illuminate first pull the fixture and check the bulb, its fixture, and connection spades;
• Reinstall the lamp housing. It is very easy to short out the lamp housing to the body by removing it or reinstalling it so check its fuse once reinstalled;

• Pull apart the pigtail connection to the switch that is part of the engine lid lower latch and short out the wiring harness plug normally attached to the switch pigtail. If the light goes on the switch may have become stuck from dried grease. Flood the latch with electrical contact
  
  cleaner spray while cycling the latch several times using a screwdriver to set the latch and pulling the release lever on the latch to release it. If the issue is resolved lightly grease the capture mechanism with a very small amount of white lithium grease, release the latch and close the lid;
• Close the engine compartment lid before going to the next step.

• Check the frunk compartment lamp function (alarm/immobilizer related):

• If the lamp simply won't illuminate: 
• First, pull the fixture and check the bulb the fixture, and its connecting spades.
• Reinstall the lamp housing. It is very easy to short out the lamp housing to the body by removing it or reinstalling it so check its fuse once reinstalled;
• Also, its connection spades come loose easily so make sure they are fully seated and don't ground to the underside of the hood sheet metal when the fixture is installed
• Pull apart the pigtail connection to the lower latch switch that is part of the frunk hood lid latch and short out the wiring harness plug normally attached to the switch pigtail. If the light goes on the switch has become stuck from dried grease. Flood the latch with electronic cleaner spray while cycling the latch several times using a screwdriver to set the latch and pulling the release lever on the latch to open the latch.  If the issue is resolved lightly grease the capture mechanism with a very small amount of white lithium grease, release the latch and close the frunk lid.
• If the lamp simply won't go out; 
• Check the lamp fixture's connection spades don't ground to the hood when installed;
• If the frunk light won't go out when closing the hood latch with a screwdriver try unplugging the lower hood latch switch pigtail, 
• If the lamp goes out when the latch pigtail is unplugged the switch in the latch has become stuck from dried grease. Hose out the latch with electronic cleaner spray while cycling the latch several times using a screwdriver to set the latch and pulling the release lever on the latch to open the latch.  If the issue is resolved lightly grease the capture mechanism with a very small amount of white lithium grease, release the latch and close the hood;
• If the light still doesn't go out with the latch pigtail unplugged the problem lies with the dome lamps, the glovebox lamp, their switches, or the controller as they all share an integrated function with the alarm/immobilizer;
• Close the frunk lid before going to the next step in this process.
• Check the glovebox lamp function (alarm/immobilizer related):
• The lamp should illuminate when the glove box is opened and go out just before it is fully closed and latched. If it stays on inspect the plunger switch's function and its installation to see if it is being adequately compressed when the door to the glove box is closed; 
• If not working correctly it will cause a fault;
• If the glovebox lamp won't illuminate check the fuse it shares with the frunk light pull and inspect the bulb and fixture then pull and test the switch by simply shorting it out and see if the lamp illuminates indicating a bad switch;
• Once any issues with the glove box lamp are resolved close the glove box before going to the next steps below.
• Checking the dome lights(NOT alarm/immobilizer related):
  
  
  
• If one of the dome lights illuminates but the other does not check the problem fixture's rocker-lens switch position. It should be in the center dome-light-off when the doors are closed position. 
• If it is, pull and inspect the bulb, fixture, and its connections;
• If neither fixture illuminates pull both fixtures and check the bulbs, the fixtures, and their wiring for a loose or pulled-off connection spade.
• Once both fixtures are reinstalled check the fuse in the frunk fuse box; 
• If both lamps fail to go out when the lamp rocker is in the center position and the key fob is used to lock the doors or the doors are simply closed and the lamps remain illuminated after a short timed period the problem lies elsewhere;
• Checking the door jamb switches (alarm/immobilizer related):
• If the dome lights fail to illuminate open both doors.  If opening a second door causes the dome lights to illuminate the door jam switch on the door that did not cause the dome lamps to turn on alone has a bad or dirty switch or its wiring harness connection has come loose. 
• Rebooting the alarm/immobilizer:
• Disconnect and reconnect the car battery to reset any internal corruption in the controllers.
• Ignition Keyway Switch: 
•  The ignition lock has a switch referred to as "Switch Buzzer Ignition Lock" that senses that the ignition key has been removed and the deadbolt to lock the steering column has been triggered The switch's connection can be seen as the bi-post plug along the shank of the ignition switch steering lock bolt assembly in the picture to the right. The switch may be broken but more likely just stuck or dirty from dried lubricant;
  
  
  
• Try cleaning the switch by flooding the ignition keyway with a spray electronic cleaner using the thin extension tube that comes with the spray can. 
• Then insert and turn the key clockwise past the unlock position then; 
• Turn it counterclockwise and remove the ignition key;
•  Turn the steering wheel slightly if necessary to assist in locking the steering column;  
• Reflooding the keyway and repeating the sequence several times and see if it resolves the issue; 
• Put a square of cardboard over the floor carpet under the keyway to capture any solvent and old lubricant that may drip under the dash during this process;
• Be aware that the ignition lock assembly needs never be replaced as both of its switches can be replaced and a locksmith who works with automotive locks can service its mechanical components avoiding the $1000+ expense of having a new lock purchased from the dealer and keyed to your car.  
• This particular procedure is prompted by others' suggestions that the stuck switch may be the cause of a flashing fob warning lamp in the clock indicating a fault. Once cleaned put a very small amount of light oil on an ignition key and insert and remove it from the keyway a few times to lubricate the lock cylinder pins. Over-lubrication of the lock may cause problems down the road as dust and debris will tend to gum up the lock.

If after working through the above one still has an issue it may be the alarm or ignition immobilizer controllers under the seats. If you have problems with the remotes working with fresh batteries one can consider the fix described on this page.

Here is what the  993 Master  - Tore from Bergvill F/X Electronics suggests on the  topic of a parasitic electrical drain that causes a dead battery when a 993 is left standing and is related to the above topic:
https://www.bergvillfx.com/categories/964993-current-measurement

Continuous flashing Immobilizer light that does not extinguish:.

In addition to the above if you find the immobilizer light in the clock seems to flash continuously as you drive the car and doesn't extinguish after a short period check the state of charge of the car's battery as the Immobilizer doesn't seem to like a weak (low voltage) battery. Some have also suggested detaching and reattaching the car battery may also clear the continuous flashing issue.

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