Intermittent ABS and STC Service lights
 

Hi Folks:

I recently purchased a 2000 S80 2.9 with 105k miles.

I've been fixing little issues along the way (battery, bulbs, tires, etc) but now have a new problem.

Most recently, the car is intermittently showing both the ABS service and STC service warnings. This doesnt happen every time I drive the car - but when they come on, they stay on for the duration of my trip.

The car had a "check engine" light. I took it to a shop, they pulled the code for O2 sensor and replaced one of them. Problem solved. Told them about my intermittent warnings - but they didnt find anything...

I dont want to get in the situation that I spend my time and money going back and forth to the shop because the warnings dont come up when they test it (and you KNOW they wont!). :confused:

Have any of you experienced this? Any ideas would be appreciated.

OK - So no help from forum members - but I did find the probable problem/solution.

Looking around at the ABS posts i found a link to the CA guy who rebuilds sensors and on his page I found the following:

On the S80 and some T5 models with STC, you will see the ABS, STC and warning triangle light turn ON. In addition, you may see a warning message in the message display window that reads "Brake Failure", "Stop Immediately".

Volvo ABS Problems

This seems to be similar symptoms to what I am seeing. I emailed the guy and will replace my sensor using his service. Hopefully this will fix the issue.

glad you did the search 1st and found something. Most of the problems are solved simply by searching this forum FIRST.
Well hopefully yours works out. Let us know how you fixed it. :)

ABS and STC lights on intermittently
 

Orygun - I have this same issue. My car is a 1999 S70 T5. Check engine light is on / off intermittently. Now the ABS and STC triangle lights are coming on - not every trip, but occasionally. If I shut the motor off, it usually resets and the lights extinguish. Did you find that replacing a sensor fixed the issue and if so, which sensor was it? Did the O2 sensor solve the Check Engine light issue? Many thanks,

FLSalomon
Pace, FL

It is most likely your ABS sensor - I replaced mine and it solved all the issues. Your warning lights will eventually become more frequent/last longer - eventually the car will more or less disable itself. Mine never got to that point. I went to Vic Rocha for a rebuilt sensor. He has easy instructions for replacement. The cost was $200.00 - Note: He claimed to give a $50 rebate for the old core, but he never paid me.

The rebuild abs sensor did the trick.

His web site: Volvo ABS Problems

Hi,
I have a 2001 S60 and the ABS/STC light is on. No other lights are on and my brakes were just checked for state inspection. I was thinking that automatic breaking and steering, etc. is a non-essential thing so I am not worrying since I also had the urgent brake warning and determined that I was low on brake fluid. I have had many Volvos and have been driving them since 1976: 2 1968 240s, 1986 wagon 250?, and now an 1988 s40 as well as the S60. My 240 has over 200k miles and the S60 had nearly 100K.

Ok so you can top off your brake fluid for now but considering its a closed system you have to look for where that fluid went to before you have a catastrophic failure. Inspect calipers and wheel hoses for leaks, inspect around the master cylinder/booster, and inspect the ABS pump area. The ABS / STC warnings can be caused by a few things - bad sensors (at the wheels), oil on the axle near the sensor ring (typically from a torn CV boot), a failed ABS pump or as noted Orygun, a failed ABS controller module (incorrectly id'd as a sensor - this is the device bolted to the ABS pump to actuate the solenoids in the pump to toggle pressure to the wheels. the controller's circuit board can develop cracks in solder joints leading to intermittent errors. As the cracks worsen the error codes become more frequent).

stc-abs
 

I had my car checked for leaks, brakes, etc. and had that fixed.
I do not use any "automation" when I drive so I don't know if cruise control works or not. The lights are intermittent and there seems no rhyme or reason that it comes on. I spoke to my service advisor and he said it is probably the abs/stc module.

When I had a similar problem on my S40, I went used and got the module for $60. It essentially bolts onto the abs pump so there would be minimal labor involved.

stc-abs
 

Awesome, thank you. Where did you get your used part?
I used ebay to get an obscure part, i.e. small trim for my other Volvo,
an antique, 1988, 240 DL. BTW, I need an odometer, speedometer for my 240DL. Do you know where I might find a good used one, ideally with a guarantee?