Lighting - Light Sensor Warning Intermittently ON/DTC P2104

94 Light Sensor Warning Light ON Intermittently (DTC 02104)

94 12 71

2010214/7

March 19, 2012.

Supersedes Technical Service Bulletin Group 68 number 08 - 08 dated November 5, 2008 for reasons listed below.





Affected Vehicles





Condition

Technical Background

Light Sensor Warning Light ON Intermittently





Customer concern: Automatic headlight instrument cluster warning light illuminating for 1 second accompanied with a short beep.

Condition: Only occurs when headlight switch is in AUTO position.

DTC "P2104/29 - G399 short to ground sporadic" is usually stored in vehicle electrical system control module -J519-.

Tip: The above DTC may be erased if the fault code does not occur again within 40 driving cycles.





Models Affected

This TSB applies ONLY to the above vehicles equipped with automatic headlights. These vehicles will be equipped with rear view mirror part number 8E0 857 511 B+ (color code) which has an integral light sensor.

Production Solution

Not applicable.

Service

Check for above DTC as follows:

1. Connect VAS Scantool.

2. From start-up screen select: Vehicle Self-Diagnosis >> 09 - electronic central electrics >> 02 - Interrogate fault memory.

If DTC "P2104/29 - G399 - short to ground sporadic" is stored in memory:

1. Replace interior rear view mirror (Part number. 8E0 857 511 B*).

See Repair Manual, Group 68, Interior Equipment, Interior rear view mirror, removing (automatic day/night mirror, interior rear view mirror with compass.

(*) Add color code: 4PK - Soul Black (A4, A4 Cabriolet); E59 - Light Platinum (A4); F77 - Light Aqua (A4); 1RS - Twist (A4).

2. Erase DTC using "05 - Erase fault memory".

3. Proceed to Checking Automatic Headlight Operation below.

If DTC "P2104/29 - G399 short to ground sporadic" is not stored in memory:





1. Remove interior rear view mirror.

If Supplier part number is 905-0617, 905-0702, 905-0704, or 905-0706.

1. Replace interior rear view mirror.

2. Proceed to "Check Operation of Automatic Headlights".

If Supplier part number is 905-1028, 905-1029, 905-1030, or 905-1031:

1. Further diagnosis of automatic headlight system is necessary. Do not complete this TSB.

Checking Automatic Headlight Operation





1. Place headlight switch in "AUTO" position.





Tip: Mirror should be in the installed position before performing the next step.





2. Place flashlight on windshield over light sensor. (Figure 5)

3. Headlights should turn OFF in 15 seconds.

If headlights do not turn OFF in 15 seconds:

^ Further diagnosis of automatic headlight system is necessary.

If headlights turn OFF in 15 seconds: System is operating properly.

^ Calibrate compass by driving slowly in a circle 1-2 times.





Warranty





Required Parts and Tools

Additional Information

All parts and service references provided in this TSB are subject to change and/or removal. Always check with your Parts Department and service manuals for the latest information.