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That didn't work. I was trying to get you to Bay 13.
here's the info:
ABS/TRACS Light On
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On going questions and concerns about the ABS/TRACS lights being on can be found on almost every message board that discusses Volvos. Even though the light/lights are on you still have regular brakes. Several things can cause the lights to come on, the more common causes are; 1) bad electrical portion of the ignition switch, 2) bad ABS/TRACS module, 3) failure of the hydraulic block or the pump. On a very rare instance the wheel sensors failing can be a cause. There is one other condition that could exist on the 1996 850 model only. The lights will not be on however you might notice that at slow speeds or over small bumps the ABS will activate for no apparent reason. A weak crimping of the sensor wiring directly underneath the fuse box could cause this.
If the ignition switch is the problem, you may notice that the shifter is hard to get out of park, your headlights don’t work, the seat belt light stays on, your radio may cut out, the tach will read incorrectly and the ABS light is on. A simple way to check if the switch is your problem is to wiggle the switch forward just a bit and back a bit, not enough to cause the starter to engage or the engine to die. When the switch is your problem there will be no codes set and the light will come on and go off with no logic at all. You may start your car and be driving for a while and then the light will come on, stop for a quick stop and then when you start the car up again the light is off. The ignition key should not have tons of items hanging from it; one key fob is about all that should be on the key ring. If you can cause the light to come on and go off by moving the ignition key, replace the ignition switch (electrical side) by following the instructions at Bay13. Another indication that the ignition switch is the problem is that no codes will be stored in the ABS control module. If you have a 1993 to 1995 850 you can check for codes in the A-3 socket of the diagnostic connections by the washer fill cap. 1996 and up 850s and S/V/C 70 will have to have the codes read with a Volvo Scan Tool or equivalent.
The ABS control module can be the cause of the light coming on. On the 1996 and newer ABS systems the ABS module is bolted to the bottom of the hydraulic/pump block. The most common codes that are set in the module is for the wheel sensors or the ABS pump. In most all cases the sensors check out just fine and the pump can be activated and it runs fine. You could have the codes cleared and things will be fine for a while then the light is back on again. When you start your car and then get up to about 20 MPH a very quick test of the pump is conducted, if the pump doesn’t run, the light will turn on. The next time you start your car everything works and the light could be turned off. The problem is that in time small hairline cracks could show up on the circuit board of the module causing intermittent signal loss, thus causing a code to be set and the light to come on.
To date I have not replace a hydraulic block unit on a 1996 or newer, however I have replaced a few on pre-1996 Volvos. Should a 400 series code be set, more than likely the hydraulic block will need replacing.
In the last five years I have seen one bad wheel sensor, and hundreds of bad control modules. If a repair shop should replace your wheel sensors and your problem returns, ensure that the cost of that repair (parts and labor) is carried over to what it takes to really fix the car.
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