# ABS Light and Brake Light Only During Highway Driving



## acamposac1 (Apr 10, 2015)

1996 Audi A6 (fwd) 270k miles
Like the title says, by Anti-Lock Off and Brake Light turn on when I take the car onto the highway after a couple min of driving. It seems like the slower I go, the longer it takes to turn on (45 min at 65 mph, almost instant at 80mph which is my normal speed). 
This only happens on the highway, and stays on until the car is restarted (and the abs is in fact disabled when the light comes on). 

The abs seems fine during low speed driving.

VCDS Codes:

VCDS-Lite Version: Release 1.2
Friday, 10 April 2015, 13:45:10:0


Chassis Type: 4A - Audi 100/A6 C4
Scan: 01,02,03,08,15,17,25,35

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Address 01: Engine Labels: 8D0-906-266.LBL
Controller: 8D0 906 266 A
Component: 2,8l V6/2V MPI OBD2 D03
Coding: 01042
Shop #: WSC 23247
VCID: 2A2781ABC5E7
1 Fault Found:
18014 - Rough Road/Engine Torque Signal from ABS: Electrical Malfunction
P1606 - 67-00 - Set-Point Not Reached || P1606 - 68-00 - Cylinder 1
Readiness: N/A
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Address 03: ABS Brakes Labels: 4D0-907-379-ABS.LBL
Controller: 4D0 907 379 G
Component: ABS/EDS BOSCH 5 7590
Coding: 0265109001 
Shop #: BB 37590
VCID: 321799CBED37
1 Fault Found:
00597 - Wheel Speed Impulses; Deviation
35-10 - - - Intermittent

Since the ABS module isn't pointing to a specific wheel speed sensor, it has to be the ABS module failing, right? I bought a cheap used one on eBay and installed it- same exact issue with same exact codes.
When using the measuring blocks to follow the individual wheel speeds, they all stay the same. I would like to try this on the highway, but there is a 20 km/hr limiter.

When doing the rear brakes, I inspected the rear sensors and tone rings. While the rings were rusty and dirty, I cleaned them up and still have the same issue.

All this seemed to start last year, the first time I took the car out on the highway after getting new tires. Both my mechanic and tire shop claim that this would have no impact on the Abs system (the wheel speeds look the same for each wheel in VCDS anyway), and it has to be a coincidence.

I'm all out of ideas (and so is my mechanic) on how to get this fixed, and have checked almost every single forum relating to this issue...

Let me know if you have any ideas. If not, I'll just have to wait a few more years until I get new tires to see if that was the cause. Thanks in advance for any help.


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