ABS issues

sisyphus

Veteran Member
Joined
Dec 8, 2008
Location
Appleton, Maine
TDI
99.5, '01 A4 Jetta sedans, 5 sp box, Hamman mod, Joey mod, Bilsteins, 2.00" lift
So this is weird. On my ‘01, 283k miles. Replaced the driver’s side driveshaft after a bad outer CV joint, all went well. Noticed the wiring to the ABS sensor was bad on that wheel but didn’t pay much attention to it. A week later my wife mentioned the ABS was coming on when the roads were dry. Then the light came on. I ordered a replacement sensor and put that in, and then cut back the broken wiring pretty far so I could have something to solder, reassembled everything and took it for a drive. Within 100 feet the ABS light came on.
Back into the garage, VCDS says mechanical fault on this sensor. I took it out, it looked fine, so I put it back, wire brushed the inside surface of the ABS ring as best I could for good measure, and headed back out. This time I made it about a mile and when stopping the ABS pump started doing its thing, even though it wasn’t needed but it felt…harsh. A mile later it happened again and the light came on. I will scan again but I’m pretty sure it’s gonna say the same thing.
I’m unclear how to pursue this now.
 

tgray

Veteran Member
Joined
Sep 12, 2004
Location
Marengo, IL
TDI
'02 Beetle, '05 Golf, 2000 Jetta, 2001 Jetta, 2002 Jetta
looks doesn't mean it is good. It may pay to try a new sensor if that is where the VCDS says the problem is.
 

sisyphus

Veteran Member
Joined
Dec 8, 2008
Location
Appleton, Maine
TDI
99.5, '01 A4 Jetta sedans, 5 sp box, Hamman mod, Joey mod, Bilsteins, 2.00" lift
Use VCDS to monitor wheel speeds reported by each sensor, should help to point you in the right direction.

VCDS ABS
I actually kinda did this. My laptop has to be plugged in to work, so I just spun the wheel while watching the speed on the screen. I couldn’t have seen the speedometer but the ECU saw the wheel turning to 6mph to 24’ before I stopped.
 

P2B

Top Post Dawg
Joined
Jan 11, 2006
Location
Toronto & Muskoka, Canada
TDI
2002 Jetta, 2003 Jetta, 2003 Jetta Wagon
You need to see what the sensors are reading while the ABS is engaging when it shouldn't.

An inverter capable of running an old laptop is pretty cheap, I think I paid $25 for the one I use for VCDS logging.
 

DivineChaos

Top Post Dawg
Joined
Jul 27, 2019
Location
Minnesota
TDI
mk6 jetta sportwagen tdi
I actually kinda did this. My laptop has to be plugged in to work, so I just spun the wheel while watching the speed on the screen. I couldn’t have seen the speedometer but the ECU saw the wheel turning to 6mph to 24’ before I stopped.
Could be a bad sensor or a bad tone ring. If you can, swap the sensor from side to side. Does it follow the sensor?
 

DivineChaos

Top Post Dawg
Joined
Jul 27, 2019
Location
Minnesota
TDI
mk6 jetta sportwagen tdi
The front ABS sensors are not interchangeable.
Ah. Well you'll have to pull up all 4 sensors in vag com and drive slow. See which one is off. As suggested before. Wally world sells cheap 12v to 115v adapters.
 

sisyphus

Veteran Member
Joined
Dec 8, 2008
Location
Appleton, Maine
TDI
99.5, '01 A4 Jetta sedans, 5 sp box, Hamman mod, Joey mod, Bilsteins, 2.00" lift
Ah. Well you'll have to pull up all 4 sensors in vag com and drive slow. See which one is off. As suggested before. Wally world sells cheap 12v to 115v adapters.
I guess. If I remember correctly this sensor was surprisingly pricey considering it’s just a hall sensor.
What if it’s reading correctly? That’s my biggest fear.
 

P2B

Top Post Dawg
Joined
Jan 11, 2006
Location
Toronto & Muskoka, Canada
TDI
2002 Jetta, 2003 Jetta, 2003 Jetta Wagon
I guess. If I remember correctly this sensor was surprisingly pricey considering it’s just a hall sensor.
What if it’s reading correctly? That’s my biggest fear.
It's throwing a code so unlikely it's reading correctly consistently.

I have had good results with Topran branded ABS sensors which are less than $20 each.

Is it possible the tone ring is damaged? You said you cleaned it up, but variations in clearance between sensor and ring as the wheel rotates can cause erratic readings.
 

Tdijarhead

Top Post Dawg
Joined
Nov 10, 2013
Location
Lawrenceville PA
TDI
2003 TDI Jetta Daughters Car, 2001 TDI Beetle, Daughters car, 2005 Golf TDI Mine, all 5 spds
How are your wheel bearings? Really bad bearing can allow the wheel to wobble slightly triggering the abs light.
 
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