This post and all of the information it contains are provided 'as is' without warranty of any kind, whether express or implied.
The wiring information was taken from "Bentley Publishers CD and Hardcover copy", there may be omissions or inaccuracies in information contained in this post. Before making any decision or taking any action based on the information contained in this Post, you should double/triple check information regards to the vehicle you service.
If you found that the information is inaccurate and you have found the solution post it up and I will update the post.
Most information posted is for USA and Canadian Audi C5 from 1998 to 2005 only,
The photos below shows three instrument clusters from Audi A6 C5 Series from 1998 to 2005 with Full size Center LCD,
Audi Allroad had some additional difference, some had thicker needle pointers based on engine 2.7T had thinner, 4.2 had thicker needles.

Here is the back of the instrument clusters.

You can see the difference between all the clusters .
Cluster 1 was installed in 1998 and 1999 Audi A6 models, the most visible difference it had analog clock
Cluster 2 was installed in 2000 to 2003 Audi A6 models, the most visible difference it had digital clock comparing to cluster 1
Cluster 3 was installed in 2003 to 2005 Audi A6/Allroad from 2001 models, the most visible difference it had rings added comparing to cluster 2
NOW COMPATIBILITY
Legend
- * Cluster 1 is 1998-1999 (no immobilizer, no Can-Bus)
- * Cluster 2 is 2000-2003 (no immobilizer in 2000 model, Immobilizer was added in 2001, Can-Bus was introduced in 2000+ models)
- * Cluster 3 is 2003 to 2005 (had immobilizer and Can-Bus) Audi Allroad from 2001 had this cluster
Cluster 2, and cluster 3 can fit directly into cluster 1, except the middle new plug needs to be installed and rewire connection.,
Cluster 3 can be installed into cluster 2 however it all depends if your car came with immobilizer.If your car came without immobilizer,
and you installed cluster that has immobilizer you will have little car key light ON on the tachometer , check the picture below.

This can not be disable by software, only solution is to cover with black electrical tape the opening for immobilizer light, only you will hear beeps for couple seconds when starting the vehicle.
If your car came with immobilizer , and you want to install another instrument cluster with immobilizer you need VAGCOM software from Ross Tech to program immobilizer to your car or you can have your Audi Dealer perform the service for you.
WARNING for those with immobilizer !!!
Do not start the car when you remove the cluster or when you install new one if it wasn't program to your car yet, if that happens your vehicle will start and shut down under 5 seconds and immobilizer will be activate , at that point it will not allow you to start the car until you re-install original cluster that was programmed in the car and if you unable to restart the vehicle you will have to tow your car to Audi Dealer to have them reset the immobilizer with their device
How do I know if I do or don't have immobilizer ?

ABS & Brake lights + AirBag Light on

Can you install color LCD into C5 Cluster

Here are wiring pinouts for Audi A6 1998, 1999 and 2000+ clusters
Green highlighted is what matches between the cluster with analog clock and cluster with digital clock
The remaining must be rewired , except of the CANBUS which is not present in clusters with analog clock you might run to some problems
Blue plug
BLUE 1998, 1999
1 - Terminal 15
2 - Right turn signal
3 - Speedometer output 1
4 - Vacant
5 - Fuel gauge sender
6 - Airbag
7 - Terminal 31 sensor Ground (GND)
8 - Coolant temperature
9 - Terminal 31 load Ground (GND)
10 - Oil pressure switch
11 - Engine speed (RPM) signal
12 - Terminal 61
13 - CAT
14 - Self-levelling suspension
15 - Terminal 58d
16 - Malfunction Indicator Lamp (MIL)
17 - High beams
18 - Left turn signal
19 - ABS
20 - Terminal 58s
21 - Door contact, driver's side
22 - Coolant level low
23 - Terminal 30
24 - Terminal 31 load Ground (GND)
25 - K-wire
26 - Right parking light
27 - Left parking light
28 - Speedometer input
29 - Brake fluid level/pressure
30 - S-contact
31 - Seat belt buckle
32 - Electronic Stability Program (ESP)
Blue 2000,2001 +
1 - Terminal 15
2 - Brake pad wear
3 - Speedometer output 1
4 - Not assigned
5 - Tank sensor
6 - Tank warning OBD 2
7 - Terminal 31 (sensor Ground (GND))
8 - Coolant temperature
9 - Terminal 31 (load Ground (GND))
10 - Oil pressure 2 (high)
11 - RPM signal
12 - A/C shut-off
13 - E-Gas/glow plug control
14 - Level control
15 - Terminal 58d
16 - Trailer turn signal
17 - High beam
18 - Left turn signal
19 - Not assigned
20 - Terminal 58s
21 - Driver door contact
22 - Lack of coolant
23 - Terminal 30
24 - Terminal 31 (load Ground (GND))
25 - Consumption signal
26 - Right parking lamp
27 - Left parking lamp
28 - Tachometer input
29 - Brake
30 - S-contact
31 - Speedometer output 2
32 - ESP/ASR
Green 1998, 1999
1 - Vacant
2 - Transponder 1
3 - Vacant
4 - Immobilizer
5 - W-wire
6 - Vacant
7 - Brake pads
8 - Input for outside buzzer control (currently vacant)
9 - Input for outside gong/chime control (currently vacant)
10 - Fuel tank warning output signal for Engine Control Module (ECM)
11 - Standing time output
12 - Air conditioning shut-off
13 - Parking brake
14 - Electronic throttle
15 - Side marker light
16 - Vacant
17 - Transponder 2
18 - Vacant
19 - Vacant
20 - Vacant
21 - Oil temperature
22 - Vacant
23 - Vacant
24 - Vacant
25 - Vacant
26 - Vacant
27 - Vacant
28 - Vacant
29 - Terminal 58d (outside dimmer potentiometer)
30 - Speedometer output 2
31 - Vacant
32 - Vacant
Green 2000+
1 - Not assigned
2 - Transponder
3 - Not assigned
4 - Not assigned
5 - W-wire
6 - Not assigned
7 - Right turn signal
8 - External buzzer
9 - External gong
10 - Airbag
11 - Stand-still time output
12 - Terminal 61
13 - Parking brake/BRAKE
14 - CHECK
15 - Oil level/oil temperature
16 - Not assigned
17 - Transponder 2
18 - CAN low speed (powertrain) (high +)
19 - CAN low speed (powertrain) (low -)
20 - CAN low speed (powertrain) (screen)
21 - ABS
22 - CAN low speed (comfort) (high +)
23 - CAN low speed (comfort) (low -)
24 - CAN low speed (comfort) (screen)
25 - Hood
26 - Fuel filler cap
27 - Belt buckle
28 - K-wire
29 - Outside temperature -input
30 - Terminal 58d (ext. Dimmer potentiometer)
31 - Selector range display
32 - Automatic vertical headlamp aim control system
RED 1998, 1999
1 - Fuel consumption signal
2 - Vacant
3 - Vacant
4 - Vacant
5 - Outside air temperature
6 - Selector lever position indicator
7 - Vacant
8 - Vacant
9 - Washer fluid
10 - Hydraulic pressure
11 - On-board computer reset
12 - Clock signal for radio frequency display
13 - Data signal for radio frequency display
14 - On-board computer, left
15 - Enable-signal for radio frequency display
16 - Tail lights / dimmed headlights (bulb monitor)
17 - Vacant
18 - On-board computer, right
19 - Brake lights
20 - Vacant
Gray 2000+ clusters
1 - Switch for menu control (Menu)
2 - Switch for menu control (out A)
3 - Switch for menu control (out B)
4 - Switch for menu control (Enter)
5 - CAN high speed Display (high +)
6 - CAN high speed Display (low -)
7 - CAN high speed Display (screen)
8 - not used
9 - not used
10 - not used
11 - Enable
12 - Clock-
13 - Data-
14 - Brake light
15 - Wash water level
16 - Tail light/Low beam (Light control)
17 - On board computer left
18 - On board computer right
19 - On board computer reset
20 - Remote control input for auxiliary heater
21 - Summer /Winter Switch
22 - Auxiliary heater on
23 - Push button branch 1 Navigation
24 - Push button branch 2 Navigation
25 - Push button branch Telematik
26 - not used
27 - not used
28 - not used
29 - not used
30 - not used
31 - not used
32 - not used
Can I install Audi A4, S4, RS4 cluster into Audi A6 ?
Yes you can install cluster from B5 series A4/S4/Rs4 into A6 , however you will run to problems with compatibility .
1) Audi A4/S4/RS4 have different fuel tank size than A6, so your fuel gauge will not be accurate ,
2) Audi A4/S4/RS4 dimmer is control by the knob on cluster, Audi A6 is control by a dimmer switch near headlight , so you will need to remember to control dimming from two switches
3) Software compatibility , each cluster are preloaded with different software versions, so depends on the version one or more gauges (tachometer or speedometer) will not function properly or not at all.
Best recommendation is to stay with the same cluster from the same model series .
Will cluster from 2000+ A6, Allroad, S6 with digital clock work in 1998, 1999 Audi A6 C5 Series ? *updated*
I have build a wiring conversion for 1998/1999 A6 and now I can test every cluster in my 1999 C5 A6 with analog clock. Here is what I have find out
All clusters from C5 /4B series models will partially work in 98/99 Audi A6 like Speedometer, battery, fuel , and coolant temp will function after you do full wiring conversion
Tachometer will function from cluster year 2000 and early 2001 (non-immobilizer version), clusters from late 2001-2005 (immobilizer version) I got only certain clusters working (tachometer and oil temp were not responsive) that all depends on the version of the image the cluster is loaded with at the factory.
What will not function is oil temp gauge , on 2000+ Audi A6/S6/Allroad they have integrated oil level and oil temp into one unit and this sensor is mounted into oil pan, so this sensor has two functions , and it comes under one wire into the cluster, and the cluster digest the signal for oil level and temp and displays on the cluster.
98 and 99 Audi A6 models it is all separate only oil temp is measured and shown on oil temp gauge , there is only one pin wire and only one function which cluster with digital clock do not understand the signal
oil Sensor warning light will be showing on the center LCD screen at all times, (I have no solution for this one, other then retrofit pan and oil sensor from 00+ vehicle and run new wires to cluster)
Second issue is the brake pad wear signal , digital clock cluster doesn't understand this signal only solution is to ground the wire at the cluster.
Check engine light will not work . 2000+ have CANBUS system which is used to communicate with different modules in the car like ECM ,
1998, 1999 don't have CANBUS , and there is no other way around then change wiring and modules and might be expensive to retrofit. (I didn't found solution for this one, I know kufatec use to or still is selling CANBUS module for instrument cluster in Europe, that can digest signal for check engine light and the tachometer signal )
I have 2001-2005 Audi A6/Allorad/S6 with immobilizer , which cluster I can use and is it plug & play ?
If you have Audi A6/Allroad/S6 with immobilizer you can replace with another cluster that has immobilizer from 2001-2005 however it is not plug and play right away .
In order to replace the cluster , you need to have SKC code (5 digit code) from both your original Cluster and your replacement.
And you need to program your keys to new replacement cluster.
here is more information about immobilizers
http://wiki.ross-tech.com/wiki/index.php/Immobilizer
Audi A6 uses Immobilizer 3 similar to Audi TT, and Vw Jetta/Golf MkIV
http://wiki.ross-tech.com/wiki/index...r_Generation_3
If you have questions please post them here and I will answer them to best of my ability.
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